Heat Treatment Parameters Research Articles

OPTIMIZATION OF HEAT TREATMENT REGIME FOR A NEW BIODEGRADABLE Mg-Zr-Nd ALLOY WITH ENHANCED MECHANICAL PROPERTIES

Purpose. To develop a rational heat treatment regime for a new biodegradable magnesium alloy of the Mg-Zr-Nd system, to ensure enhanced mechanical properties throughout the entire treatment period. Research methods. Differential thermal analysis (DTA) was used to determine phase transformation temperatures. Microstructure analysis was conducted using optical microscopy (“Neophot 32” and “OLYMPUS IX 70”) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SELMI RЕМ-106I). Mechanical properties were determined using an INSTRON 2801 testing machine. The influence of cooling rate on microstructure and properties was studied using ProCAST simulation software. Heat treatment was carried out in a Bellevue type shaft furnace and a PAP-4M furnace. X-ray analysis was used to detect internal defects in samples. Results. A new heat treatment regime was developed for the biodegradable Mg-3.15Nd-1.25Zr-0.6Zn (wt%) alloy. Using differential thermal analysis and microstructure studies at various quenching temperatures, the optimal quenching temperature was established at 560 °C. Empirical relationships describing the influence of heat treatment parameters on the alloy's microstructure were calculated. The new heat treatment regime (quenching from 560 °C for 8 hours, air cooling + aging at 200 °C for 16 hours) resulted in improved mechanical properties (UTS = 276–282 MPa, δ = 5.2–5.8%) compared to the standard T6 regime. Scientific novelty. For the first time, a comprehensive study of the influence of heat treatment parameters on the structure and properties of a new Mg-3.15Nd-1.25Zr-0.6Zn (wt%) alloy with increased content of alloying elements was conducted. New dependencies describing the influence of quenching temperature on the alloy's grain size were established. Practical value. A new heat treatment regime for the biodegradable magnesium alloy was developed, which ensures complete dissolution of the pseudoeutectic phase and formation of strengthening phases, resulting in improved mechanical properties compared to the standard alloy Mg-2.5Nd-0.4Zn-0.5Zr (wt%) and the standard T6 regime.

Evaluation of Post-Processing on Additive Manufactured Bioresorbable Polymers for Medical Devices.

Additive manufacturing (AM) has seen massive growth in the medical device sector and an increase in the clearance of devices. Many challenges still exist in the design, development, and clinical use of AM-fabricated devices, notably the processing, annealing, and sterilization of resorbable polymers. In addition, the use of these materials continues to grow in medical devices and scaffold technologies for tissue engineering and regenerative medicine (TERM). Specifically, this study focused on the scaffold mechanical properties post-processing and throughout a simulated resorption (in vitro) study. Herein, we evaluated three (3) materials that span a range of mechanical properties and degradation rates relating to a range of tissue healing rates and mechanical properties affording the opportunity of biomimetic potentials, Caproprene 100M, Lactoflex 7415, and Lactoprene 100M. These bioresorbable polymers were additively manufactured into scaffold forms of Type V tensile bars to investigate post-processing parameters. A range of heat treatments were then performed after the AM process to induce a range of semicrystalline morphologies, and subsequently, two different sterilization techniques were performed, one based on super critical carbon dioxide and another using electron beam radiation. It was statistically shown that the heat treatment parameters and the sterilization method had statistically significant effects on the scaffold properties of each material. While material differences were responsible for the majority of the mechanical property breadth, techniques utilizing analysis of variance allowed the observation of significant effects and interactions associated with heat treatment, sterilization, and material parameters (alpha = 0.05). The characterization of the sample groups provided insight into the process-structure-property-performance relationships of the resorbable scaffold samples. It was established that the post-processing impacted the scaffold structures, and therefore, sterilization and heat treatment selections should be included within initial design considerations alongside material selection as critical for device development, especially when AM bioresorbable scaffolds for TERM.

Influence of Solution Treatment Temperatures on LPBF-Produced Inconel 939 Alloy on Mechanical Performance

This study investigates the influence of solution treatment temperatures on the microstructure and mechanical properties of LPBF (Laser Powder Bed Fusion)-manufactured Inconel 939 alloy. The primary objectives are to assess the impact of sub-recrystallization (below recrystallization temperature) and recrystallization temperatures during solution treatment on mechanical performance under different conditions. This study validates the hypothesis concerning carbide redistribution and mechanical performance in LPBF-produced Inconel 939 parts through comprehensive analysis, including microstructure studies and tensile tests. The results indicate that higher heat treatment temperatures lead to significant changes in carbide redistribution and mechanical performance. For instance, at room temperature, the specimen with sub-recrystallization solution treatment temperature exhibited superior mechanical properties compared to both the as-built and recrystallization-temperature solution treatment specimens. However, at elevated temperatures (700 °C), a reversal in mechanical anisotropy was observed, with the vertical axis demonstrating higher tensile strength compared to the horizontal axis for all material states. Furthermore, a microstructural analysis revealed distinct changes in grain structure and precipitate distribution, particularly the migration of carbides from grain boundaries to intragranular regions. These findings underscore the importance of precise control over heat treatment parameters to achieve optimal mechanical behavior. This research provides valuable insights into optimizing LPBF processes for the Inconel 939 alloy, highlighting the need for a meticulous control of the solution treatment parameters to ensure mechanical integrity. The findings contribute to a broader understanding of material-specific responses in additive manufacturing, with significant implications for aerospace applications.

Regression Analysis and Optimum Values of Austempering Affecting Mechanical Properties of Compacted Graphite Iron.

The study examined the effect of heat treatment parameters of compacted graphite iron (CGI) on the mechanical properties of the material. The microstructure was characterized using optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Three levels of heat treatment parameters were adopted considering the orthogonal test plan 24. The effects of austenitizing temperature and time and austempering on tensile strength, yield strength, and elongation were analyzed. Polynomial regression was chosen because it extends linear regression and allows for modeling more complex, nonlinear relationships between variables. Total regression models were determined for each dataset. The models for tensile strength (Rm) had an approximately 82% coefficient of determination, for yield strength (R0.2) around 50%, and for elongation (A5) around 80%. For optimization, the response surface method (RSM) was used. The results obtained were compared with the proposed mathematical models. The ANOVO results showed that austempering temperature (Tpi) had the greatest effect on each parameter studied. The optimal conditions for the analyzed parameters, assuming tensile strength and yield strength at the maximum level and an elongation of about 0.7%, are obtained for the following heat treatment parameters: Tγ = 890 °C; Tpi = 290 °C; τγ = 120 min; τpi = 150 min.

Effect of Cu Alloying and Heat Treatment Parameters on NiTi Alloy Phase Stability and Constitutive Behavior

Effect of Cu Alloying and Heat Treatment Parameters on NiTi Alloy Phase Stability and Constitutive Behavior

Investigation of age-hardening behaviour of Al alloys via feature screening-assisted machine learning

Age hardening stands as a crucial strengthening process for aluminium (Al) alloys. However, determining the optimal ageing conditions has traditionally relied on resource-intensive trial-and-error methods. To streamline the design of Al alloys, this study introduces a novel feature screening-assisted machine learning (ML) approach to explore age-hardening behaviour across varying compositions and heat treatment parameters, focusing on yield tensile strength (YTS), ultimate tensile strength (UTS), and elongation (EL). A comprehensive pool of features, incorporating alloy composition and fundamental elemental properties, was generated to provide metallurgical insights for ML predictions. Subsequently, feature screening methodologies, including correlation analysis, feature elimination, and multi-objective genetic algorithm (MOGA), were employed to identify key features from the vast feature pool, balancing model complexity and prediction accuracy. Employing support vector regression models trained on these optimized feature sets, we demonstrate enhanced prediction accuracy for strength properties while maintaining model simplicity for EL, with minimal impact on accuracy. In addition, experimental results further validate the method's ability to reproduce ageing curves across all three mechanical properties for both commercialized and newly designed Al alloys.

Heat Treatment Optimization and Nitriding Effects on Mechanical Properties of 32CrMoV12-10 Steel

32CrMoV12-10 steel is widely utilized in industries where high strength and toughness are crucial. This alloy is commonly used in manufacturing components like gun barrels, gears, and bearings, which demand exceptional mechanical properties. These parts typically undergo heat treatments, including hardening and surface enhancement techniques such as nitriding, to extend their fatigue life significantly. It is crucial to identify optimal heat treatment conditions to achieve desired material performance. In this study, commercial 32CrMoV12-10 steel was selected to investigate the impact of heat treatment parameters (temperature, duration time, and quenching media) on its mechanical properties. To analyse the effect of these parameters, the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) and the Taguchi Method were employed, facilitating a systematic examination of the process stages and subsequent mechanical testing outcomes, including Charpy V-notch impact, hardness, and tensile strength assessments. An optimal heat treatment protocol was established based on these analyses, and the nitriding depth of the optimally treated sample was examined using a micro-Vickers hardness tester. For comparative analysis, another sample with closely related outcomes was also evaluated. Results indicated that the surface hardness of the optimally treated Sample 10 reached 870 HV, with a core hardness of 417 HV, compared to non-nitrided Sample 3, which showed a surface hardness of 860 HV and a core hardness of 415 HV. Despite the proximity in their values, Sample 10 exhibited slightly higher micro-Vickers hardness than Sample 3. However, while Sample 3 fails to meet the specified tensile stress and hardness criteria, Sample 10, produced through optimization, meets criteria, ranging from 970 to 1040 N/mm², underscoring the efficacy of the optimization process facilitated by TOPSIS. This optimization was notable for its minimal experimental requirements, proving effective in conserving time, energy, and resources while investigating the processed material.

Sensitization and Mechanical Response of Cu‐Containing Steel Rods

The iron and steel manufacturing sector significantly adds to global greenhouse gas emissions, caused primarily by the carbothermic reduction of iron ore. Recycling scrap steel offers an effective decarbonization strategy but introduces impurities like copper (Cu) that can negatively impact mechanical properties. This study investigates the effects of Cu content and heat treatment on the mechanical performance and sensitization of steel wire rods for tire manufacturing. Steel rods with 0.04 and 0.21 wt% Cu are heated to 1050 or 1200 °C, then air quenched, or furnace cooled. Tensile testing coupled with microscopic analysis is used to evaluate mechanical properties and assess the sensitization effects. Higher Cu content leads to larger sensitized zones with increased Cu precipitation along grain boundaries. Ductility and toughness, crucial for wire drawability, are found to be reduced, despite higher ultimate strength. Slower furnace cooling is seen to result in smaller sensitized zones compared to air quenching, suggesting a pivotal role of cooling rate in sensitization control. The findings provide insights into optimize heat treatment parameters and Cu content limits, balancing mechanical performance and maintaining drawability for enhanced scrap steel recycling in tire production.

Influence of the material properties on the clinching process and the resulting load-bearing capacity of the joint

This study focuses on the phenomenological change in material strength caused by a specific heat treatment and the subsequent analysis of the influence on the clinching process and the resulting joint properties. For this purpose, three series of tests were performed. In the first series of tests, the influence of heat treatment up to 340 °C on the mechanical properties of an age-hardenable AlMgSi alloy was investigated. Holding time and temperature were varied and the material strength was evaluated by tensile and hardness tests. Two strength-increasing and two strength-reducing heat treatment parameters were identified. In the second series of tests, selected heat treatment parameters were applied to a larger number of specimens and the joint strength was investigated by shear and head tensile tests. In the shear tensile test, mainly the properties of the punch-side material have an influence on the resulting joint strength. A change in strength of the die-side material can be neglected. In contrast, the properties of both sheets are important in the head tensile test. The strength of the joint will only increase if the strength of both sheets is increased. In general, a strength increasing heat treatment resulted in higher joint strength. In the third series of tests, the factor of punch displacement was considered, which was demonstrated to directly influence the formation of the clinched joint geometry.

Optimizing the effect of heat treatment on the mechanical properties (tensile Strength and hardness) of Hyphaene Thebaica nut; A machine learning and Taguchi approach

The demand for innovative and sustainable biomaterials in healthcare and biotechnology has fueled the need for advancements in its engineering performance. However, the limited properties of biomaterials without the integration of synthetic reinforcements or supports pose a challenge. Consequently, there is a growing necessity for the development of full cycle eco-friendly materials. This study focuses on enhancing the mechanical properties of Doum palm nuts through heat treatment for engineering applications. The research employs the Taguchi optimization technique and genetic algorithms to determine the optimal combination of heating temperature and holding time, aiming to achieve the highest tensile strength and hardness. The results showcase the effectiveness of the proposed approach, revealing the optimal tensile strength of 7.32 MPa at a treatment temperature of 50 °C and a holding time of 120 min. Similarly, the optimum hardness of 60.3 Hv is attained at a heat treatment temperature of 100 °C and a holding time of 120 min. The study further investigates chemical changes through Fourier transform infrared analysis and optical micrographs. Regression models for tensile strength and hardness are developed, and the global optimum is found using a genetic algorithm solver. The findings of this study demonstrate significant and remarkable improvements in the mechanical properties of biomaterials, highlighting their potential for demanding engineering applications. The optimized heat treatment parameters provide a path towards enhanced biomaterials performance and offer promising avenues for the development of tougher and more resilient materials. This research contributes to the field of biomaterials engineering, paving the way for the design and production of eco-friendly materials with superior mechanical properties, thus addressing the ongoing demand for innovative and sustainable solutions in various industries.

The Impact of pH on Fouling and Related Physicochemical Properties of Skim Milk Concentrate during Heat Treatment Using a Laboratory-Scale Fouling Rig.

The objective of this study was to investigate the effect of pH (6.1, 6.3, 6.5, and 6.7) on heat-induced changes in concentrated skim milk as related to fouling in heat exchangers. Skim milk (30%, w/w, total solids) was recirculated in a laboratory-scale fouling rig at an initial target temperature of 85 °C for 90 min to simulate thermal processing and preheating of evaporated liquid concentrate feeds in dairy processing. This study investigated key changes in relevant physicochemical properties, such as viscosity, particle size, and sedimentation, as major contributors to fouling at lower pHs (6.1 and 6.3). Additionally, protein aggregation and calcium phosphate precipitation were identified as significant contributors to fouling deposits. Possible strategies to mitigate fouling were determined, including optimizing pH and adjusting heat treatment parameters to minimize protein denaturation and mineral deposition. The findings indicate that carefully controlling pH and processing parameters can greatly enhance the efficiency of milk concentration by evaporation and tailor finished product quality. Moreover, this study showed that monitoring of CIP solutions for protein content and turbidity provides valuable information on the intensity of fouling and the efficiency of cleaning.

DEVELOPMENT OF INNOVATIVE TECHNOLOGY AND HARDENING EQUIPMENT FOR THE IMPLEMENTATION OF HARDENING HEAT TREATMENT OF METAL PRODUCTS USING FLUIDIZED BULK MATERIALS (PART 1)

Statement of the problem. One of the main problems faced by a modern enterprise is the search for ways to improve the efficiency of its activities. For the effective functioning of the thermal units of toolmaking industries, the simultaneous availability of heating and quenching devices with different heating and cooling media is required. This explains the desire of manufacturers and scientists to find technological, cheap, environmentally friendly heating and cooling media that can provide the required heat treatment parameters and high quality of the processed parts. The purpose of the article is to analyze the state-of-the-art of hardening thermal (combined) treatment methods using bulk materials as media for volumetric heating and forced cooling of metal products and the design and technological features of hardening devices that can ensure a rational structural state of metal parts of complex geometric shapes with a minimum level of their warping and deformation on the example of using vibro-fluidized bulk materials (in the technical literature, the term vibro-gravity particles of heat is used). Research results. To analyze the results of tests of bulk materials as quenching media for high-alloy steel grades and their effect on the structure and properties of the metal in comparison with the traditional oil quenching regime. To consider the features of quenching devices that use mechanical vibration to produce vibro-s bulk material and the possibility of their use in the implementation of quenching modes (including isothermal) of steel products of complex geometric shapes. Conclusion. The use of fluidized bulk materials in industry as media for volumetric heating and hardening of metal products and the design of devices for their use has been investigated. The advantages of the fluidized bed cooling method for the effective implementation of hardening heat treatment regimes are determined. It is shown that this method of forced volumetric cooling of toolmaking products is rational in terms of various indicators. The structural and technological parameters of devices for its implementation are analyzed, which can consistently provide the required level of properties of alloyed and high-alloy tool steels with a minimum level of warping and deformation.

Thermodynamic prediction and experimental verification of phase transformation kinetics in 3Mn steel with Ti and V microadditions

AbstractIn this work, the phase transformation kinetics and precipitation processes were studied using thermodynamic calculations and a dilatometric method to determine the optimal chemical composition of medium-Mn steel and its initial parameters of heat treatment. The investigated steel is intended for forgings with the microstructure composed of bainitic matrix and retained austenite (RA). An influence of Al and Si on the Ms temperature was characterized to obtain the best chemical composition in terms of RA stabilization. Theoretical continuous cooling transformation (CCT) and time–temperature transformation (TTT) diagrams were determined and compared with dilatometric results. Microstructural observations were compared with the dilatometric results. The hardenability of steel was high due to increased Mn and Mo additions. A very small fraction of cementite is expected in the microstructure due to Al and Si additions. The shortest time to start and finish the bainitic transformation was noted for the isothermal heat treatment at 420 °C. The completion of the bainitic transformation took about 25 min and is acceptable from the industrial point of view. The obtained results constitute a good basis for designing thermomechanical processing routes of bainitic steels with RA.

Precipitation behavior and performance evolution of cold-rolled cu-Ti-Fe alloy during heat treatment

The CuTi alloy is extensively utilized for its high strength, excellent elasticity, and processability. Heat treatment processes are crucial for affecting the microstructure and properties. The effects of different aging processes on the microstructure and properties of cold-rolled Cu-Ti-Fe alloy were investigated, and the heat treatment parameters were optimized. The results show that the cold-rolled Cu-Ti-Fe alloy exhibits excellent comprehensive performance at 450 °C for 2 h, with the hardness of 342.2 HV, the electrical conductivity of 16.1 % IACS, and the tensile strength of 1051 MPa. The aggregation of solute atoms occurs in the early stages of aging. The uniformly distributed β'-Cu4Ti phase precipitates at peak aging, which has a coherent relationship with the matrix. The precipitation of Ti atoms enhances the electrical conductivity of the alloy, and the movement of dislocations is prevented by precipitates, increasing the strength. During the over-aging stage, the precipitates transform into β-Cu4Ti phases, losing complete coherency with the matrix. The coarsening of precipitates leads to the softening of the Cu-Ti-Fe alloy. Theoretical calculation results indicate that the thermal diffusion ability of solute atoms is the strongest and precipitates completely when the alloy aged at 450 °C. The precipitation strengthening mechanism plays a significant role in improving the strength.

The Influence of Microstructure and Process Design on the Plastic Stability of 4 wt% Medium‐Manganese Steels

The influence of different microstructures on the plastic stability of an air‐hardened industrially produced medium‐manganese steel is presented. For this matter, heat treatment parameters before and during intercritical annealing (IA) are varied, to achieve different microstructures. The resulting duplex microstructure is consecutively tested by tensile tests, which are monitored by digital image correlation (DIC) to obtain information on the local plastic deformation. The tests are accompanied by microstructure investigations using optical, scanning electron, and transmission electron microscopy. Finally, X‐ray and electron backscatter diffraction experiments are performed before and after deformation, to describe the altering phase fractions. It is demonstrated that the effect of the deformation temperature prior to IA treatment has a significant influence on the duplex microstructure, as it changes the austenite morphology from lamellar to globular and increases the phase fraction. The change in austenite phase fraction and morphology results in a higher yield strength (≈100 MPa), as well as higher uniform and total elongations (+2% and +5%, respectively). The DIC and tensile tests reveal that these differences in the austenite phase lead to a complete change in the strain hardening behavior, from continuous flow to discontinuous serrated flow, with clearly visible deformation bands during plastic deformation.

STUDY OF THE EFFECT OF AGING DURING CHEMICAL AND THERMAL TREATMENT ON THE STRUCTURE AND PROPERTIES OF STEEL 18ХГТ AND 20Х

The paper proposes a study of the effect of chemical and thermal treatment on the structure and properties of the grid of the agricultural separator made of 20X steel. As a comparative analogue of this steel, the grating of an agricultural separator made of 18ХГТ steel was used, from which test samples were made to determine the mechanical properties and microstructure. The data of the study allowed us to expand the understanding of the formation of the structural component and the influence of heat treatment parameters, namely cementation, on mechanical and operational properties.

Exploring W-EUROFER brazed joints: S/TEM and nanoindentation analysis following post-brazing tempering treatment

Tempering treatments are essential for restoring the hardness and microstructure of EUROFER steel when W-EUROFER joints are formed at temperatures exceeding the steel's austenitization point (890 °C). This post-brazing heat treatment can, however, alter the microstructure and thereby affect the mechanical properties. This study explores the microstructural and nanomechanical effects in the brazed area of W-EUROFER joints following this heat treatment, utilizing copper as an intermediate filler material. Using Scanning Transmission Electron Microscopy (STEM) with Energy Dispersive Spectroscopy (EDS) on FIB lamellae and nanoindentation techniques we examined the stability and phase characteristics of the post-tempered microstructure in two lamellae that covers the whole phases of the braze microstructure.The tempering process enhances copper diffusion and the growth of copper precipitates without significantly altering the joint's overall microstructure. Despite the general stress-relief effects of tempering, which typically lower mechanical properties, the diffusion phases formed during brazing maintained high hardness and modulus, indicative of a complex, element-rich composition. A reduction in mechanical properties was observed in the iron-rich phase near the W-braze interface and the EUROFER base material, aligning with the purpose of the heat treatment. However, the copper braze and tungsten base material largely retained their stability and resilience to thermal treatments.This research provides vital insights into the behavior of these material systems under thermal processing, highlighting the necessity of optimizing heat treatment parameters to preserve joint integrity in high-performance applications such as nuclear fusion reactors. The findings contribute significantly to the development of durable and reliable materials for fusion energy, emphasizing the importance of controlled tempering processes to enhance material properties.

Two‐stage annealing method for short carbon fiber‐reinforced nylon 6 in fused filament fabrication

AbstractThe mechanical properties of short carbon fiber‐reinforced nylon 6 (CF‐PA6) components formed by fused filament fabrication (FFF) are significantly affected by the process parameters of additive manufacturing and heat treatment. In this study, the effects of printing speed, carbon fiber aspect ratio, and annealing temperature on fiber orientation were investigated by observation of single‐layer‐single‐fiber samples. Furthermore, a two‐stage annealing process was proposed to increase the tensile modulus of CF‐PA6 based on the correlation analysis results between the degree of fiber alignment and the variation of tensile modulus. According to the calculation of the Pearson correlation coefficient, the tensile modulus was highly correlated with the degree of fiber alignment under different printing speeds and fiber aspect ratios. The variation in tensile modulus and fiber orientation was also consistent when the annealing temperature was lower than the crystallization temperature. Conversely, the variation of tensile modulus and fiber orientation were opposite, as the annealing temperature was higher than the crystallization temperature because of the influence of crystallinity. Through increasing the degree of fiber alignment and crystallinity of the parts, the proposed two‐stage annealing method could increase the tensile modulus of the parts to 9.0 GPa, which was 16.81% higher than that of single‐temperature annealing.Highlights The effects of annealing temperature, carbon fiber aspect ratio and printing speed on fiber orientation were illustrated. The relationship between the degree of fiber alignment and the variation of tensile modulus was established. The proposed two‐stage annealing method, considering fiber orientation and crystallinity, significantly increased the tensile modulus of CF270‐PA6 parts from 7.7 to 9.0 GPa. The quantitative analysis of the fiber orientation is realized by the statistical analysis of the plane fiber orientation angle of the single‐layer‐single‐fiber sample.

Microstructural evolution and mechanical properties of maraging steel by additive manufacturing

Laser powder bed fusion (LPBF) is a revolutionary and innovative technology that provides advanced technical support for the forming of parts with high precision and complex structures. In this work, a new type of Fe-Ni-Mo-Ti-Al-Y cobalt-free maraging steel was successfully fabricated by LPBF. The additive manufacturing parameters and the microstructural evolution of cobalt-free maraging steel under different heat treatment parameters were systematically studied. The results show that the parts without cracks and close to complete density can be fabricated under a wide LPBF process window. The dislocation cell with 500 nm in the printing state makes the material have good plasticity. After post-heat treatment, the preferred orientation of LPBF maraging steel is reduced, but the typical characteristics of molten pool and cellular structure in maraging steel disappeared, which is the result of local composition and microstructure homogenization. The elongation of LPBF maraging steel in solution annealed state is higher than that in as-printed state, which is due to the reduction of dislocation density and grain coarsening. However, after direct aging, due to the formation of nano-sized Ni3(Ti, Mo) precipitates in the matrix, the mechanical properties of the material were effectively enhanced, and the tensile strength increases from ∼1.1 GPa in as-printed state to ∼1.6 GPa in aging state. In contrast, the corrosion resistance of as-printed maraging steel is higher and comparable to that of traditional cobalt-containing maraging steel. However, the corrosion resistance of LPBF maraging steel after being aged is reduced, which is due to the existence of precipitates and dislocations. This study provides a theoretical reference for the composition design and strengthening mechanism of LPBF cobalt-free maraging steel.

Rotating bending fatigue behavior of high-pressure diecast AlSi10MgMn alloy based on T5 heat treatment parameters

Abstract The study investigates fatigue failure, a common phenomenon in machine elements subjected to cyclic stresses. The analysis emphasizes that the actual stress experienced by materials often falls below their tensile and yield strengths due to repetitive variable stresses, leading to fatigue damage. Fatigue life is measured by the number of cycles endured before failure. This paper focuses on the aluminum alloy of AlSi10MgMn, extensively used in manufacturing due to its strength, low density, and corrosion resistance. Experimental procedures encompassed tensile testing, microstructural examination, SEM analysis, and fatigue testing. Tensile tests provided initial stress values for fatigue testing. Microstructure analyses verified that heat-treated samples exhibited precipitates. SEM analysis disclosed microstructural characteristics, while fracture surface examinations demonstrated higher fatigue resistance in heat-treated specimens. Hardness measurements were conducted, with heat-treated samples showing higher values. Theoretical calculations based on stress and cycle numbers were compared to experimental fatigue results. The derived equations aligned well with the tests. Ultimately, the study underlines the importance of heat treatment on material behavior and fatigue resistance, shedding light on alloy performance and durability enhancement.