Chip Morphology Research Articles

The Behaviour of carbon quantum dots and cryogenic cooling in turning of super duplex F 53 steel

The objective of this research is to examine how various cooling and lubrication techniques affect the machinability of Duplex F53 steel when turning it, with particular attention to residual stress, surface roughness, chip morphology, tool wear, machining temperature, and crystallographic structures. According to the microstructure analysis, the presence of additional austenite grains at high temperatures during dry machining results in an increase in hardness. On the other hand, cooling techniques including liquid nitrogen (LN2), carbon Quantum dots with SQL (CD), and oil with small quantity lubrication (OSQL) produce larger ferrite grains, which lower hardness. According to residual stress analysis, the high temperatures during dry cutting result in increased strains, which are successfully mitigated by lubrication. The two-phase microstructure has a crucial influence in mechanical characteristics, as demonstrated by X-ray diffraction (XRD) studies, wherein finer grains improve surface polish but demand more energy. Measuring surface roughness (Ra) reveals that adhesion wears during dry machining raises Ra, while OSQL and LN2 cooling lower Ra and improve surface quality. Tool performance is negatively impacted by high machining temperatures. Cutting temperatures and friction are greatly reduced by LN2 cooling. Dry machining increases tool wear because of the high temperatures and absence of lubrication; OSQL and CD lower wear rates, while LN2 offers the best protection for tools. Thinner, better-separated chips are produced by effective lubrication in OSQL and LN2, while thicker, more deformed chips are produced by dry machining, according to chip morphology and thickness analyses. The study leads to the conclusion that super duplex steel's surface quality, tool life, and machinability can all be significantly enhanced by carbon quantum dots and cryogenic cooling.

Microarchitectural properties of compacted cancellous bone allografts: A morphology micro-computed tomography analysis

Massive bone loss poses a significant challenge in defect reconstruction. The use of compacted allografts is a valuable technique to reconstruct bone stock. This study aimed to assess the impact of compression on the microstructure of native cancellous bone chips with a micro-CT analysis.Bone samples were harvested from 15 femoral heads donated by patients who underwent total hip arthroplasty. Bone chips were prepared using a bone mill. All samples with the same weight were compressed by 25% and 50% of their original volume and subsequently scanned with a micro-CT scanner to determine the microarchitectural morphology of the bone chips. Uniaxial compression test was carried out before and after a standardized compaction procedure.Comparing the samples without compaction to 50% , the number of trabeculae doubled, the volume ratio doubled, and the trabeculae spacing was reduced, showing voids of 800 μm on average. The number of interlocking possibilities tripled, while no differences were seen in the trabeculae morphology. Uniaxial compression test showed a yield limit after compaction of 0.125 MPa.Interlocking might occur three times more with a denser material than in a non-compacted sample. The increase in density comparable to manual intraoperative compaction did not lead to significant fragmentation of the allograft material. The assessed microarchitecture should, therefore, reassemble the intraoperative situation during a manual bone impaction procedure.

Experimental Investigation of the Micro-Milling of Additively Manufactured Titanium Alloys: Selective Laser Melting and Wrought Ti6Al4V

AbstractIn recent years, additive manufacturing (AM) has gained popularity in the aerospace, automobile, and medical industries due to its ability to produce complex profiles with minimal tolerances. Micro-milling is recommended for machining AM-based parts to improve surface quality and form accuracy. Therefore, the machinability of a titanium alloy (Ti6Al4V) manufactured using selective laser melting (SLM) is explored and compared to that of wrought Ti6Al4V in micro-milling. The experimental results reveal the surface topology, chip morphology, burr formation, and tool wear characteristics of both samples. The micro-milling of AM-based Ti6Al4V generates a surface roughness of 19.2 nm, which is 13.9% lower than that of wrought workpieces, and this component exhibits less tool wear. SLM-based Ti6Al4V produces continuous chips, while wrought Ti6Al4V yields relatively short chips. Additionally, SLM-fabricated Ti6Al4V exhibits smaller burrs after micro-milling than wrought Ti6Al4V. Despite the higher hardness of SLM-based Ti6Al4V, it demonstrates better machinability than wrought Ti6Al4V, resulting in better surface quality with lower tool wear levels and shorter burr heights. This study provides valuable insights into future research on postprocessing AM-based titanium parts, especially using micro-milling.

Effects of tool coating and tool wear on the surface and chip morphology in side milling of Ti2AlNb intermetallic alloys

Effects of tool coating and tool wear on the surface and chip morphology in side milling of Ti2AlNb intermetallic alloys

Tribological characteristics of SiALON ceramic inserts during sustainable machining of Inconel 625 based on comprehensive chip morphology analysis

Tribological characteristics of SiALON ceramic inserts during sustainable machining of Inconel 625 based on comprehensive chip morphology analysis

Comparative study on machinability and surface integrity of γ-TiAl alloy in laser assisted milling

γ-TiAl alloy, as a typical difficult-to-cut material, is considered to have great potential in aero-engine manufacturing. However, it is difficult to achieve high-quality processing of γ-TiAl alloy using traditional cutting processes, due to the room temperature brittleness and high strength of theγ-TiAl alloy. This study proposes a fiber laser assisted machining (LAM) method to improve the cutting quality of γ-TiAl alloy, which attempts to address current challenges in applications of aero-engine manufacturing. The machinability and surface integrity of γ-TiAl specimens using LAM method and conventional milling are analyzed and discussed. Through cutting force testing, chip morphology research, surface hardness testing, and microstructure observation, it is found that the LAM method significantly improves the machinability and machined surface integrity of γ-TiAl specimens. Furthermore, the cooling strategies in LAM is discussed through comparative cutting experiments. During continuous LAM processing, it is found that the rapid heat accumulation effect induces tool adhesive wear, which leads to the decline of cutting quality and tool failure. The experimental results indicate that liquid cooling is an available strategy to reduce tool wear. However, it should be noted that periodic thermal shock by liquid cooling causes surface roughness to increase in continuous LAM processing. Through this work, it is proved that the LAM method can improve machinability and surface integrity of γ-TiAl specimens, which has great potential and worths further studies.

Research on tool wear and breakage state recognition of heavy milling 508III steel based on ResNet-CBAM

Milling water chamber head material 508 III steel belongs to extreme manufacturing, and the tool failure is very serious in the process of machining. How to monitor and identify the tool wear damage state in time and effectively is a key problem to be solved urgently. Identifying chip morphology changes under machining conditions plays a very important role in characterizing tool wear and breakage. Tool wear has an important influence on the chip morphology during the process of milling 508III steel, and changes in chip morphology can also reflect the tool wear and breakage state. Therefore, this paper takes the chip morphology image as an important feature for tool wear and breakage recognition, and uses Gaussian fuzzy estimation morphology method to preprocess the chip morphology image. Build a ResNet network combined by convolutional block attention module (ResNet-CBAM) tool wear and breakage recognition model, and explore the selection of the model backbone network, determination of the ResNet backbone network depth, and fusion methods of different attention mechanisms. Through the ablation experiment and visual analysis of the attention mechanism module, it is verified that the ResNet-CBAM model proposed in this paper has an accuracy rate of 96.67% in tool wear and breakage state recognition, especially in the stage of severe tool wear and breakage. This study realizes the prediction and early warning of tool life, and provides effective guarantee for the efficient cutting of large parts of high-end equipment and the stable operation of manufacturing system.

Chip formation analysis during dry turning of C45 steel

Machining is a material removal process that creates surfaces through chip formation using a cutting tool. The morphology of the chips and the mechanisms governing their formation directly affect the quality of machined parts. This experimental study examines chip formation mechanisms in the dry turning of C45 steel under various cutting conditions, utilizing coated carbide inserts. Machining performance was evaluated based on key chip morphology parameters, including shape, length, thickness, and volume. The results show that increasing cutting speed (Vc) produces shorter, thicker chips without significantly altering their predominantly helical shape. A higher feed rate (f) maintains the tangled ribbon form of the chips but leads to longer chip production. Additionally, changes in the depth of cut (ap) create instabilities that result in varied chip morphologies, including long tubular, short helical, and elementary forms. As the depth of cut increases, chips become shorter and thinner. These findings provide valuable insights into the material's deformation and fracture mechanisms, enhancing our understanding of chip formation and its impact on the efficiency of dry turning operations on C45 steel.

High-speed turning of AISI 4340 alloy steel using carbide tools in a sustainable minimum quantity lubrication environment

Purpose This study aims to investigate the machining performance of CVD-coated carbide tools by considering most crucial machinability aspects: cutting force, tool life, surface roughness and chip morphology in high-speed hard turning of AISI 4340 alloy steel under a sustainable minimum quantity lubrication (MQL) environment. Design/methodology/approach The purpose of this study is to analyze the performance of coated carbide tools under MQL environment therefore, machining tests were performed in accordance with the Taguchi L9 orthogonal array, accommodating the three crucial machining parameters such as cutting speed (V = 300–400 m/min), feed rate (F = 0.1–0.2 mm/rev) and depth of cut (DOC = 0.2–0.4 mm). The measured or calculated values obtained in each experimental run were validated for normality assumptions before drawing any statistical inferences. Taguchi signal-to-noise (S/N) ratio and analysis of variance methodologies were used to examine the effect of machining variables on the performance outcomes. Findings The quantitative analysis revealed that the depth of cut exerted the most significant influence on cutting force, with a contributing rate of 60.72%. Cutting speed was identified as the primary variable affecting the tool life, exhibiting a 47.58% contribution, while feed rate had the most dominating impact on surface roughness, with an overall contributing rate of 89.95%. The lowest cutting force (184.55 N) and the longest tool life (7.10 min) were achieved with low machining parameters at V = 300 m/min, F = 0.1 mm/rev, DOC = 0.2 mm. Conversely, the lowest surface roughness (496 nm) was achieved with high cutting speed, low feed rate and moderate depth of cut at V = 400 m/min, F = 0.1 mm/rev and DOC = 0.3 mm. Moreover, the microscopic examination of the chips revealed a serrated shape formation under all machining conditions. However, the degree of serration increased with an incremental raise with cutting speed and feed rate. Research limitations/implications The study is limited to study the effect of machining parameters within the stated range of cutting speed, feed rate and depth of cut as well as other parameters. Practical implications Practitioners may consider to adopt this machining technique to create more sustainable working environment as well as eliminate the disposal cost of the used metal cutting fluid. Social implications By applying this machining technique, diseases caused by metal cutting fluid to the mechanist will be significantly reduced, therefore creating better lifestyles. Originality/value Hard turning is commonly carried out with advanced cutting tools such as ceramics, cubic boron nitride and polycrystalline cubic boron nitride to attain exceptional surface finish. However, the high cost of these tools necessitates exploration of alternative approaches. Therefore, this study investigates the potential of using cost-effective, multilayer-coated carbide tools under MQL conditions to achieve comparable surface quality. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2024-0013/

Finite Element Simulation of Ti-6Al-4V Alloy Machining with a Grain-Size-Dependent Constitutive Model Considering the Ploughing Effect Under MQL and Cryogenic Conditions

The finite element modeling method has been widely applied in the modeling of the cutting process to characterize the instantaneous and microscale deformation mechanism that was difficult to obtain using physical experiments. The lubrication and cooling conditions, such as minimum quantity lubrication and cryogenic liquid nitrogen, affect the thermo-mechanical behaviors and machined surface integrity in the cutting process. In this work, a grain-size-dependent constitutive model was used to model orthogonal cutting for Ti-6Al-4V alloy with MQL and LN2 conditions. The cutting forces and chip morphologies that were measured in the cutting experiments of Ti-6Al-4V alloy were used to validate the simulated forces. The relative errors between the measured and simulated principal forces were less than 8%, while the relative errors of thrust forces were less than 19%. The predicted chip morphologies and surface grain refinement agreed well with the experimental results under the conditions with different uncut chip thicknesses and edge radii. Additionally, the relationship between the plastic displacement and grain refinement, as well as the microhardness and residual stresses under MQL and cryogenic conditions, were discussed. This work provides an effective modeling method for the orthogonal cutting of Ti-6Al-4V alloy to understand the mechanism of the plastic deformation and machined surface integrity under the MQL and LN2 conditions.

The Effects of Alloy Composition and Surface Integrity on the Machinability of Austenitic Stainless Steels 304 and 304L

Austenitic stainless steels, such as 304 and 304L, are extensively utilized in diverse industries due to their favorable properties, including biocompatibility, high durability, ductility, toughness at cryogenic temperatures, and excellent corrosion resistance. Additionally, these steels exhibit notable resistance to fatigue and oxidation. Despite these advantages, they are challenging to machine due to characteristics such as high work hardening, built-up edge formation, and low heat conductivity. The material 304L distinguishes itself from material 304 through its lower carbon content, making it more resistance to corrosion. 304L is experiencing a consistent rise in industrial demand. It is anticipated that this advanced material will progressively supersede 304 in various applications. The variability in alloy compositions and surface integrity of blanks can influence the tool wear and may even lead to abrupt tool breakage, necessitating supervision during machining operations. This study delves into the correlation between the alloy compositions, micro structure, surface integrity, and machinability of these special steels, focusing on turning processes. Various blanks of 304 and 304L in the form of bars, sourced from different manufacturers, were utilized in the study. These blanks exhibited slight variations in alloy composition (albeit within the standard range) and differed in the state of surface integrity characterized by variations in microstructure, grain size, microhardness, and residual stress. All blanks (across this array of materials) were subjected to turning using the same tool specifications and sets of machining parameters for comparative analysis. Various machinability indicators, including cutting forces, surface roughness, burr formation, tool wear, and chip morphology, were thoroughly examined. The findings highlight that the key factors influencing machinability include the microhardness of the surface and the residual stress state in the subsurface of the bars before the turning process. In contrast, changing the alloy composition within the standard range has hardly any effect on the machinability of these steels. The machinability of the examined specimens was adversely affected when the hardness exceeded 350 HV from the surface up to 2 mm below the surface and simultaneously the surface compressive residual stress exceeded −130 MPa.

Machinability Performance of Single Coated and Multicoated Carbide Tools During Turning Ti6Al4V Alloy

AbstractThis paper presents the machinability performance of uncoated, single-coated, and multicoated carbide tools during turning of Grade 5 (Ti6Al4V) Titanium alloy, which is challenging to machine due to its distinctive material properties. Coated tools with single-coated Titanium Aluminium Nitride (TiAlN) and multi-coated layer of Titanium Aluminium Nitride with Aluminium Chromium Nitride (TiAlN + AlCrN) coated inserts were utilized to assess surface roughness (Ra), tool wear rate (R), and chip morphologies under various cutting conditions using dry machining. Analysis of the used tools revealed that coated tools exhibited improved tool life and surface quality compared to uncoated tools across all cutting conditions. Multi-coated tools of TiAlN + AlCrN demonstrated a tool life increase of up to 15% compared to uncoated and single-coated tools, with surface roughness improvements ranging from 30 to 45% depending on cutting speed. Chip morphology analysis indicated an increase in the chip reduction coefficient with higher cutting speeds for all tool types. Coated tools exhibited the lowest chip-reduction coefficient due to the presence of TiAlN and AlCrN coatings, which control the tool chip contact length. Conversely, uncoated chip morphology resulted in larger chip thickness values compared to coated tools, particularly at cutting speeds above 100 m/min, attributed to poor heat dissipation and chemical reactions at the tool chip interface. Energy dispersive X-ray scanning electron microscopy (SEM/EDXS) analysis of worn uncoated inserts revealed a higher tendency towards Titanium adhesion compared to coated tools. The proposed multi-layer coatings of (TiAlN + AlCrN) used for dry machining proved highly beneficial for achieving economic machining objectives and may reduce the need for lubrication when processing Ti6Al4V alloys.

Wear behavior of novel CVD-coated wiper inserts’ with various chip-breakers and resulting surface integrity during dry drilling of Ti-6Al-4V

In this paper, a comprehensive investigation in terms of tool wear/life, chip morphology, surface roughness/damage, diametric error, burr height, and microstructure is conducted by using an innovative integration of peripheral wiper and central stepped inserts when drilling Ti-6Al-4V alloy in a dry-cutting environment. Two geometries of peripheral wiper inserts termed as LM (groove width-1000 mm, groove depth-65 mm) and GT (groove width-720 mm, groove depth-20 mm) are evaluated at two levels of cutting speeds (50 m/min and 60 m/min) and three levels of feed rates (0.10 mm/rev, 0.15 mm/rev, and 0.20 mm/rev) while keeping the geometry of central stepped insert constant. The GT wiper configuration is found to be more suitable in terms of tool life, drilling maximum number of holes (75) at a cutting speed of 50 m/min and feed rate of 0.10 mm/rev which is ∼3-fold higher than that of the LM geometry. With respect to majority of the drilled hole attributes, better performance of LM geometry is observed in comparison to its GT counterpart due to its improved chip breakability. In addition, all holes are oversized ranging from 30 µm to100 µm. Minor plastic deformation of grain boundaries in the machined sub-surface is noticed to a depth of 10–15 µm in the direction of cutting.

A review on progress trends of machining of Carbon Fiber Reinforced Plastics

In contemporary manufacturing industries, composite materials such as carbon fiber reinforced plastics (CFRPs) have become indispensable, finding extensive applications in aerospace, automotive, shipbuilding, high-tech sports equipment, and more. The exceptional chemical, physical, and mechanical properties of CFRPs, including high corrosion resistance, superior strength-to-weight ratio, high fatigue strength, and oxidation resistance, make them highly sought after. However, these very advantages pose significant challenges during machining due to the abrasive nature of composites, anisotropic mechanical properties, and poor thermal conductivity, which collectively exacerbate tool wear. This review paper addresses the critical need for innovative solutions to improve the machinability of CFRPs, a subject of paramount importance for advancing manufacturing efficiency and product quality. It comprehensively examines the latest research progress, current practices, and emerging trends in machining techniques such as turning, drilling (including reaming and countersinking), milling and grinding. The review delves into the influence of various cutting conditions, environments, and tool geometries. It also examines tool textures, materials, and coatings. Additionally, advanced machining methods, including vibration, thermal, and hybrid-assisted machining, are discussed. These factors impact key performance metrics such as cutting forces and torques, tool wear and life, chip morphology, surface roughness, and the quality of machined surfaces, including defect analysis. By synthesizing a vast array of literature for the first time, this paper highlights the most effective strategies to enhance machinability while extending tool life and improving surface finish. Notably, it underscores the innovative use of dry and flood lubrication, minimum quantity lubrication, cryogenic lubrication, and high-pressure cooling. Additionally, it emphasizes optimizing cutting tool geometry, employing diamond tools, and coating tools with TiN and TiAlN, alongside the application of heat treatment and hybrid machining methods, particularly those incorporating vibration machining techniques. This review not only identifies the current challenges but also proposes cutting-edge solutions, making it an essential resource for researchers and practitioners aiming to push the boundaries of CFRP machining technology.

Investigation on the material removal mechanism in ion implantation-assisted elliptical vibration cutting of hard and brittle material

Ductile-regime machining has been used to generate damage-free surface of hard and brittle materials by setting the cutting depth to be smaller than the ductile-brittle transition depth (DBTD). However, the ductile-regime cutting of sapphire remains challenging owing to its extreme hardness, small DBTD, serious surface fractures, and severe tool wear. To solve this problem, ion implantation-assisted elliptical vibration cutting (Ii-EVC) has been proposed in this study to enhance the machinability of hard and brittle materials. Taking sapphire as an example, high-energy phosphorus ions were implanted into the workpiece to modify its surface. Nanoindentation tests revealed that the modified materials undergo plastic and elastic deformation more easily due to the decrease in hardness and modulus. Compared with nanocutting without implantation assistance, the DBTD of implanted sapphire has been increased by more than five times. The advantageous effects of Ii-EVC achieve great enhancement in machinability, including surface fractures suppression, tool-wear reduction, chips morphology transformation from discontinuous to continuous, and cutting force decrease. Furthermore, even near the cracks in the brittle region after Ii-EVC, the subsurface microstructure showed a more complete lattice arrangement and a strain distribution close to zero, indicating that crack propagation was effectively suppressed. Due to the promoted localized plastic deformation, the stress distribution in the implanted material is much smaller than that in pristine workpiece. Implantation-induced defects not only serve as a core for absorbing external energy from the high-frequency vibration and improving the in-grain deformation but also facilitate the formation of shear bands. The interface with high distortion between the modified layer and substrate can effectively dissipate strain energy and hinder crack propagation to the free surface. The turning experiments verified that Ii-EVC can achieve better surface quality, less tool wear and higher optical transmittance. Overall, Ii-EVC addresses the challenges of tool breakage and surface fracture caused by high-frequency collision between tool and workpiece in traditional EVC, overcomes the problem of limited modification depth in ion implantation, and increases the ductile-regime removal depth of extremely hard and brittle materials to several microns. Such findings demonstrate that Ii-EVC is a promising method for the ultra-precision manufacturing of advanced materials.

A study on mechanisms of saw-tooth chip formation in hard turning under hybrid nanofluid-assisted MQL environment

Saw-tooth chip generated from hard turning is one of the most distinguishing features with conventional turning process. The presented work aims to contribute an extensive understanding the formation mechanism and main parameters of saw-tooth chips in oblique hard turning of 90CrSi hardened tool steel (60–62 HRC). The effects of dry, Al2O3 nanofluid MQL, Al2O3/MoS2 hybrid nanofluid MQL conditions on the serrated chip formation were experimentally investigated in terms of chip morphology, chip color, segment spacing, serrated segmentation frequency, and shear angle. The obtained experimental results indicated that, due to the better cooling and lubricating performance of nanofluid and hybrid nanofluid, the shear angles ϕ increase about 91.73% and 94.88% respectively when compared to dry cutting, which makes the formation of saw-tooth chip more favorable. Moreover, the analysis of microstructure image of the back side of chip proves the better lubrication from ball roller and tribo-film formation of Al2O3 and MoS2 nanoparticles. Based on the chip morphology analysis, the shear angle ϕ, the degree of chip segmentation on the top side in the chip’s transverse section K2, and the chip deformation coefficient in the transverse section K3 should be used as the additional criterions to evaluate the frictional improvement in cutting zone.

Experimental investigation on sustainable machining of monel using vegetable oils as cutting fluids and machine learning-based surface roughness prediction

Abstract The material processing industry is anticipated to mitigate environmental degradation. The protocols established by the International Organisation for Standardisation were adhered to. As a result, it would be prudent to investigate the feasibility of minimizing the use of synthetic cutting fluids from the machining process. This study discusses an environmentally-friendly machining technique for turning nickel-based alloy Monel-500, which evaluates four different cooling conditions: dry machining, flood machining, Co-MQL (coconut oil), and Rb-MQL (Rice Bran Oil). These conditions were tested by experimenting with various machining parameters to investigate four aspects of the turning process: surface finish,cutting temperature, tool wear and chip morphology. Rice bran oil is considered eco-friendly compared to synthetic cutting fluids, and employing it in minimum quantity is economical and helps improve the machined workpiece’s surface finish. The investigation has been further extended by applying machine learning algorithms to predict surface roughness, utilising two logical regressions implemented in Python. Among the two machine learning approaches, the random forest regression technique has demonstrated superior results, achieving a prediction accuracy of 99.8%. Consequently, a decision tree has been developed using this regression model to predict the surface roughness. The structured analysis of the decision tree provides more accurate conclusions, offering flexibility in adjusting parameters and expanding options for operation. As a result, the decision tree approach enables the efficient utilisation of production resources and enhances production capacity by making informed choices about cooling methods during the turning process. Rb-MQL has performed better in all aspects than the other three cooling conditions. When comparing machining under dry conditions, flood cooling, Co-MQL, and Rb-MQL (rice bran oil) reduce the tooltip temperature by 39.5%,25.45 and 24.11%, respectively. Rb-MQL reduced surface roughness by 28.23%,43.59 and 60.49% in contrast with machining under dry, flood, and Co-MQL.

Improving surface integrity of GH4169 alloy through magnetic-assisted cutting

GH4169 alloy presents superior properties such as high strength and resistance to high temperature, but possesses poor machinability. To ameliorate the problem and improve the machined surface integrity of GH4169 alloy, this paper focused on the application of magnetic-assisted cutting (MAC) for GH4169 alloy. In the MAC process, a permanent magnetic field (the magnetic field intensity is 0.25 T) was applied to the workpiece material during cutting, and its impact on chip morphology, tool damage and surface integrity was investigated. By comparing to traditional cutting (TC), the introduction of a magnetic field results in a reduction in the chip thickness and minimizes chip serration, leading to smoother cutting process and reduced fluctuations in cutting forces. Meanwhile, the introduction of magnetic field resulted in a substantial decrease in the notch wear and abrasion of cutting tool, and mitigated the excessive growth of built-up edge (BUE), which improved the tool life and machined surface integrity. By analyzing the machined surface at the end of TC and MAC, it was found that the surface roughness at the end of MAC was reduced by 22.4 %. Meanwhile, the cavity, side flow and debris of BUE, which tend to occur in the machined surface during the TC process, are effectively suppressed after MAC. Furthermore, Microstructural analysis of the machined surface indicated an enhancement in the dislocation density on the machined surface layer, suggesting the magnetoplastic effect of the magnetic field on GH4169 alloy.

Effect of materials and process parameters on machinability of stainless steels

Stainless steels, recognized for their corrosion resistance attributed to a minimum of 11 % Chromium, encompass a variety of alloys with distinctive microstructures and properties. Machinability significantly varies among these alloys. Austenitic steels such as SS303 and 304 present challenges, demonstrating poor surface finish and high power consumption. This study, employing a central composite design, investigates the machinability of AISI 303, 304, 316, AISI 416, and AISI A36. Turning tests with PVD TiAlN-coated inserts revealed optimal parameters for cutting speeds (90.5256–244.411 m/min), feed (0.0635–0.4826 mm/rev), and depth (0.00016–0.00187 m.). Surface finish analysis identified AISI 316 as the best, closely followed by AISI 303. From a power consumption standpoint, AISI 303 performed the best, and concerning fragmented chip morphology, AISI 303 also excelled. The superior performance of AISI 303 is attributed to 2 % Manganese and 0.15 % Sulfur, proving to be the most effective combination compared to the other four steels, resulting in a higher percentage of MnS2, optimal for improving machinability. The depth of cut emerges as the most influential factor affecting dimensional accuracy. These findings hold practical significance in the selection of stainless steels and corresponding process parameters across various industries, including the manufacturing of heavy earthmoving equipment. By shedding light on the optimal composition and machining conditions, this study contributes valuable insights for enhancing performance and efficiency in stainless steel applications.

Study on the critical conditions for ductile-brittle transition in ultrasonic-assisted grinding of SiC particle-reinforced Al-MMCs

High volume fraction (45 %) silicon carbide particle-reinforced aluminum matrix composites (SiCp/Al-MMCs) play a significant role in various engineering fields due to their outstanding performance. However, damages characterized by SiC particle fracture during machining lead to poor surface integrity, which severely affects the fatigue performance of SiCp/Al composite structural components. Ultrasonic-assisted grinding (UAG) is acknowledged as beneficial for promoting ductile grinding in hard and brittle materials. This study focuses on the critical conditions for ductile-brittle transition in ultrasonic-assisted grinding of SiCp/Al composites and develops a mechanism and data driven model of critical undeformed chip thickness (UCT) for ductile grinding to accurately predict the material removal mode. The model thoroughly integrates considerations of chip morphology, removal mode transition mechanism, and grinding surface damage characteristics. Response surface methodology (RSM) and genetic algorithms (GA) were utilized to correct the impact of processing parameters on the removal regime. Experiments on ultrasonic-assisted side and end grinding were conducted to thoroughly discuss the effects of different undeformed chip thicknesses, grinding speeds and ultrasonic vibration amplitude on surface damage and the critical conditions for the ductile-brittle transition. The findings corroborate the experimental data with the predicted values. Ultrasonic vibration can effectively reduce the brittle fracture of SiC particles in SiCp/Al composites. Appropriately increasing the grinding speed and reducing the chip thickness can enhance the critical chip thickness for ductile grinding and decrease the proportion of brittle surfaces, thereby achieving a balance between surface integrity and grinding efficiency. This research provides guidance for high-performance machining of SiCp/Al composites.