Types Of Serrations Research Articles

Molecular dynamics of CH4 adsorption and diffusion characteristics through different geometric shale kerogen nanopores

In shale, pore structure plays an extremely significant effect on CH4 storage and transportation in a reservoir, especially for the reservoir involving large amounts of extremely tiny nanopore and variance of microstructure. In this study, three molecular dynamics models for different types of kerogen nanopores such as serration type, arc type and great-wall type are established, validated and implemented to assess the impact of pore structure on CH4 adsorption and diffusion behaviors in kerogen matrix and nanopore at temperature 320 ∼ 380 K, pressure 5 ∼ 20 MPa and pore size 3 ∼ 5 nm. The simulation results demonstrate that the CH4 density in the bulk of serration-type, arc-type and great-wall-type pores is 1.6, 1.3 and 1.9 higher than that inside kerogen molecules. Increasing temperature can weaken the adsorption capacity of kerogen, but the serration-type pore is the most sensitive to temperature. Regardless of the pore type, increasing pressure can significantly enhance the adsorption capacity of kerogen which is almost unaffected by pore size, whereas the CH4 diffusion coefficient increases with pore size. Furthermore, the great-wall-type pore can adsorb more CH4 molecules due to its smooth surface, followed by change in the arc-type and serration-type pores in turn. Among these types of pores, the CH4 diffusion coefficient is the most insensitive to the size of arc-type pore. Hence, the influences of kerogen pore structure under different conditions of temperature, pressure and pore size are quantified in this work to improve a comprehensive understanding of CH4 adsorption and diffusion behaviors in shale, thereby contributing to high-efficient and sustainable development of shale gas reservoirs.

Effect of temperature on dynamic strain aging and intermediate temperature embrittlement of nickel-based alloy N06625

Due to its excellent mechanical properties and good corrosion resistance at low to intermediate temperatures, nickel-based alloy N06625 has gradually become an ideal material for high-temperature gas-cooled reactor evaporators in nuclear power plants. It is currently receiving more and more attention. In this work, the tensile test of nickel-based alloy N06625 was carried out at room temperature to 900℃. The dynamic strain aging (DSA) process and microstructure evolution were studied by electron back-scatter diffraction (EBSD). The dynamic strain aging and intermediate temperature embrittlement of nickel-based alloy N06625 in the temperature range 25–900℃ were systematically studied. The results show that the stress-strain curve exhibits a serrated shape at 200–700℃, and with the increase in temperature, the serrated type changes from type A to type A+B and type C. The type A and type (A+B) serrations are related to the diffusion of interstitial carbon atoms. The interaction between substitutional elements Cr and Mo and movable dislocations causes the type C serration. As the temperature increases, high-density dislocations accumulate at the grain boundaries, and the proportion of substructural grains increases. A brittle fracture occurs at 600–800℃. The fracture mechanism may be due to the stress concentration at the grain boundary caused by the appearance of micropore, which weakens the grain boundary's strength and promotes the grain boundary's early failure. The continuous increase of strain makes the micropore fuse and grow to form a crack source.

Serrated flow stress in the CoCrFeNi multi-principal element alloys with different grain sizes and added Re

Multi-principal element alloys have attracted extensive attention as a new alloy design concept. In particular, the CoCrFeNi alloys with low stacking fault energy have excellent tensile plasticity and fracture toughness at both low and room temperature, and good phase stability at high temperatures, considered a new type of structural material with great potential. Multi-principal element alloys exhibit plastic instability termed serrated flow, at certain strain rates and temperature ranges. The serrated flow stress is usually closely related to dynamic strain aging, which reflects dislocation and barrier processes and impacts the mechanical properties of alloys. In the present study, CoCrFeNi alloys were selected as the research object, and the impact of grain size and the addition of Re elements on the serrated flow stress behavior was investigated. The results showed that in the tensile tests at 600 °C, the serrated flow stress behavior occurred in the fine-grain specimen only at a lower strain rate. The tensile curves of the coarse-grain specimen at different strain rates all show serration. Overall, the serrated type changes with the decreasing grain size, the increasing strain rate, and the addition of Re element, all of which result in a decrease in the magnitude and number of serrations and a weakening of the serrated behavior.

The influence of additive manufacturing on Portevin-Le Châtelier (PLC) effect in Ni–Co-based superalloy

The microstructures and tensile properties of the Ni–Co-based superalloys made by additive manufacturing (AM) were investigated. The results revealed that both normal and inverse Portevin-Le Châtelier (PLC) effects were observed in AM Ni–Co-based superalloys. In addition, AM significantly inhibited the PLC effect, the average stress decrements for the cast and wrought (C&W) alloys with the same nominal compositions were more than ten times as large as those for the AM alloys when tested at 400 °C with a strain rate of 3 × 10−4 s−1. In the AM Ni–Co-based superalloys, type C serrations had connections with the inverse PLC effect. Transmission electron microscope (TEM) was performed to investigate the interactions of solute atoms, dislocations, stacking faults (SFs) and the γ′ phase for a deep insight into mechanisms of the PLC effects and clarifying the changes in serration types and the conversion from normal to inverse PLC effect.

Effect of Si on the deformation behavior of retained austenite and annealed martensite in medium Mn steels

The present study systematically investigated the effect of Si additions from 0 to 4 wt % on the deformation mechanism of a Fe-0.2C-6.8Mn (wt. %) medium Mn steel. The duplex microstructure consisting of film-like retained austenite (RA) and lath-shaped annealed martensite (AM) was produced for different Si alloyed steels by annealing treatments. They have similar volume fraction of RA. The effect of Si content on the dynamic strain aging (DSA) of RA and the serration type of tensile curves, as well as the fine structure evolution within AM during deformation was studied in detail. For the different Si alloyed steels, their tensile curves all exhibit flow serrations, accompanied with the propagation of the Portevine-Le Châtelier (PLC) band caused by DSA in RA. The serration type was sensitive to Si content. For the high Si steel, only type B serrations appear. This is attributed to the high Si content in RA, promoting aged dislocations by C atoms due to the repulsive interaction between C and Si atoms. For the low Si and Si free steels, type A serrations occur after type B serrations disappear at a certain strain. The mechanical stability and Mn/Si contents of RA play an important role in the PLC band propagation. The Si content has also an important effect on the evolution of dislocation configuration within AM during deformation. In the low and Si free steels, the dislocation multiplication and tangles, as well as the formation of dislocation walls, dividing up the laths appear in the AM. While in the high Si steel, it is found that the dislocation cells appear within the AM due to Si addition promoting the formation of screw dislocations by neutron diffraction technique, and the cross slip of screw dislocations as a necessary mechanism for dislocation cell formation. The formation of dislocation configuration with low energy is believed to be another essential factor improving the mechanical properties, besides the transformation-induced plasticity effect. This work paves a new pathway towards tailoring dislocation configuration for designing a new generation advanced high-strength steel.

The influences of vanadium addition and temperature on the microstructure, and mechanical properties of Al0.1CoCrFeNiVx multi-principal element alloys

The study aimed to examine the crystal structure, microstructure, microhardness, and tensile properties of Al0.1CoCrFeNiVx (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) multi-principal element alloys. Both Al0.1CoCrFeNi and Al0.1CoCrFeNiV0.2 alloys were single FCC phase solid solutions. σ-phase precipitated in Al0.1CoCrFeNiV0.4 alloy. The volume fraction of σ-phase increased as V content increased from x = 0.4 to 1.0. The volume fraction of σ-phase in Al0.1CoCrFeNiV alloy was found to be 48.4 vol%. It was shown that to predict the phase composition of multi-principal element alloys containing σ-phase employing solid solution formation model, coupling it with criteria of σ-phase formation was necessary. Moreover, when the V content was x ≤ 0.4, the alloys showed good toughness and ductility (> 49%). However, a continuous increase in V content led to a higher volume fraction of σ-phase, which enhanced the strengthening/hardening effect until reaching the embrittlement threshold. At x = 0.4, the alloy exhibited a better balance between strength and plasticity. Uniaxial tensile tests were performed on the annealed Al0.1CoCrFeNiV0.4 alloy at different temperatures. Results suggested that the alloy retains excellent plasticity (> 45%) at 500 ℃. Nevertheless, it exhibited a decrease in strength and plasticity with elevated temperatures. The addition of V caused a significant increase in ultimate strength and elongation at mid-temperatures (500–700 ℃) compared to Al0.1CoCrFeNi alloy. The engineering stress-strain curves of the Al0.1CoCrFeNiV0.4 alloy displayed serrated flow at temperatures from 300 ℃ to 700 ℃. The serration type transitioned from A-type to C-type as the temperature rose.

Design of a Pendulum Impact Cutter to Measure Plant Stalk Cutting Force and Energy

Aims: A research study was conducted to examine how the blade type, cross-sectional area of stalks and moisture content of the crop is affecting the cutting energy and cutting force needed for the harvesting of blackgram and greengram stalks. A pendulum impact cutter was developed for the measurement of cutting energy and force.
 Methodology: The plant was positioned in the stalk holder to replicate the natural arrangement of stalks in a field. Three types of blades such as smooth edge, V-shaped and serrated type were used for the present study.
 Results: The experimental findings indicated that an increase in the cross-sectional area of blackgram and greengram stalks resulted in higher cutting energy and cutting force requirements for all the three types of blades. The decrease in moisture content of greengram and blackgram crops leads to increase in cutting energy and cutting force by all the three blades. The reason for increase of cutting energy and cutting force at low moisture content i.e., both plant materials exhibit a fibrous property at low moisture content which holds a higher strength. So, more cutting energy and cutting force is required for cutting at low moisture contents. The serrated type blade exhibited lower cutting energy and cutting force requirements in comparison to the smooth edge and V-shaped types of blades across all stalk diameters. Among three blades, serrated blade is best for cutting of green gram and black gram, which reported less cutting energy and force. The following functional relationship is drawn from this research i.e., the cutting energy and cutting force is directly proportional to the cross-sectional area of stalks and inversely proportional to the moisture content of the crop.

On the normal and inverse Portevin–Le Chatelier behavior in hot rolled Inconel 617 superalloy

In the present study the effect of hot rolling process on the normal and inverse Portevin-Le Chatelier behavior was investigated. The hot rolling process was carried out at 950 °C, 1050 °C, and 1150 °C to capture the effect of thermomechanical process on elimination or postponing of dynamic strain aging phenomenon in Inconel 617 during subsequent deformation process. The tensile test was performed within the temperature range between 350 °C and 750 °C at a constant strain rate. The microstructure evaluations were carried out by optical microscope and scanning electron microscope. The serrated flow was observed in the stress-strain curves at specific temperatures. The type of serrations changed from type B to type C at the strain rate of 5 × 10−4 s−1 as the tensile test temperature was enhanced. The change of normal PLC effect to the inverse PLC effect was intensified when the hot rolling temperature was increased; Hence, the inverse PLC effect was observed at 750 °C in the sample which had rolled at 1150 °C. Whilst the serrated flow was not seen at 750 °C in the samples which had rolled at 950 °C and 1050 °C. The critical strain, for the initiation of the serrated flow was found to reduce with the increasing temperature of hot rolling from 950 °C to 1150 °C. After tensile test, the microstructural evaluations revealed the proven substantial role of precipitation of γ′ and the Cr-rich M23C6 carbides in pinning of the mobile dislocations, which led to the inverse PLC effect.

Dynamic strain aging behavior of an advanced alumina-forming austenite stainless steel based on Fe–30Ni–15Cr–3.5Al

Alumina-forming austenite (AFA) steels have emerged as promising candidate materials for ultra-supercritical units because of their excellent high-temperature performance. Dynamic strain aging (DSA) can increase the strength, but at the expense of plasticity, which will inevitably reduce the service life of materials. The aim of this study was to determine the serration behavior of a new AFA steel from room temperature (RT) to 700 °C at different strain rates from 1.33 × 10−5 s−1 to 1.33 × 10−2 s−1. Serrations were found at 300–650 °C under the tested conditions. Regardless of the strain rate, three types of serration arose: type A, A + B, and C. Plateaus of yield strength, ductility minima, and sensitivity to negative strain rates were observed. Ludwik's relationship was more accurate than Holloman's relationship for expressing the relationship between the true stress and the true strain during plastic deformation. Below 600 °C, the critical plastic strain showed a positive DSA, but it showed an inverse DSA above 600 °C. The value of (m+β) at the normal DSA was 2.27, and the activation energy was 81.624 kJ/mol. Depending on the value of the activation energy, the DSA was attributed to pinning dislocations by substitutional aluminum atoms. SEM examination of the fracture surfaces revealed mixed mode with dimples and facets at tested temperature, but facts fracture became more intense with increasing temperature and ductility minima arose at 650 °C. The results of transmission electron microscopy showed increase interaction of dislocations with solute atoms with increase in the temperature up to 700 °C.

The Portevin-Le Chatelier Effect of Cu-2.0Be Alloy during Hot Compression.

The Portevin-Le Chatelier effect of Cu-2.0Be alloy was investigated using hot isothermal compression at varying strain rates (0.01-10 s-1) and temperature (903-1063 K). An Arrhenius-type constitutive equation was developed, and the average activation was determined. Both strain-rate-sensitive and temperature-sensitive serrations were identified. The stress-strain curve exhibited three types of serrations: type A at high strain rates, type B (mixed A + B) at medium strain rates, and type C at low strain rates. The serration mechanism is mainly affected by the interaction between the velocity of solute atom diffusion and movable dislocations. As the strain rate increases, the dislocations outpace the diffusion speed of the solute atoms, limiting their ability to effectively pin the dislocations, resulting in lower dislocation density and serration amplitude. Moreover, the dynamic phase transformation triggers the formation of nanoscale dispersive β phases, which impede dislocation and cause a rapid increase in the effective stress required for unpinning, leading to the formation of mixed A + B serrations at 1 s-1.

Small punch investigation of the dynamic strain aging behaviour and intermediate temperature embrittlement of Inconel 625

In this study, the deformation behaviour and mechanical property evolution of Inconel 625 were studied at different temperatures and deformation rates by using small punch test (SPT). With the increase in the temperature, small punch characteristic parameters decreased, and an approximate platform was found in the temperature range of 300–600 ℃. The dynamic strain aging (DSA) characteristics were observed in the load-displacement curves over a similar temperature range. To analyse the small punch DSA behaviour, the serration types, critical displacement, and maximum load drop were examined. The serration types changed from Type A to Type C when the temperature increased or the deformation rate decreased. The abnormal DSA was proven at around 600 ℃. Then, the influence of the strain rate was analysed and the intermediate temperature embrittlement was found at 600–700 ℃ as the strain rates decreased. Considering the difference between the SPT and the uniaxial tensile test, the influence of stress triaxiality on DSA was discussed. The similar change rule of serration types was presented. SPT was proven to be a reasonable method to evaluate the DSA behaviour which could replace uniaxial tensile test.

Effect of rolling temperature on the occurrence of dynamic strain aging of Inconel 617 superalloy

Inconel 617 specimens were hot rolled at 950 °C, 1050 °C, and 1150 °C to examine the effect of thermomechanical processing on the occurrence of dynamic strain aging (DSA), followed by performing the tensile tests at temperature range of 350 °C–750 °C with the strain rates of 5 × 10−4 s−1, 5 × 10−3 s−1, and 1 × 10−2 s−1. The microstructural evolution was studied by an optical microscope, a scanning electron microscope (SEM), and differential scanning calorimetry (DSC). The stress-strain curves were analyzed in terms of serration intensity and types. The serrated flow at temperature range of 450 °C–750 °C underwent changes by the strain rate and the temperature, and the serration type changed from types A + B and B to type C. The transformation of Portevin-Le Chatelier (PLC) effect from normal to the inverse PLC effect was observed at a temperature higher than 550 °C. The activation energy was calculated and it was found that the diffusion of Cr and Mo substitutional atoms are mainly responsible for the DSA effect in hot rolled Inconel 617 superalloy. The hot rolling temperature was also found to have a significant impact on the occurrence of DSA. Moreover, it was indicated that as the hot rolling temperature increases from 950 °C to 1150 °C, the occurrence of dynamic strain aging is intensified.

On the characteristic of ultrafine/nano precipitates and serration behavior in an Al-doped Fe3Cr2Ni multi-principle-element alloy

In this research, a class of Co-free Fe3Cr2NiAlx (x = 0–1.1) multi-principle-element alloys (MPEAs) with ultrafine/nano precipitates and serration behavior were fabricated. By varying Al element levels, the microstructure changed from a dual-phase structure of face-centered-cubic (FCC) plus body-centered-cubic (BCC) to a tri-phase structure of plate-like FCC, BCC and a uniformly dispersed nano-sized ordered B2 precipitates within BCC, then transformed to another dual-phase structure of BCC and the dual-morphology ultrafine/nano B2 precipitates within BCC. The increasing Al content resulted in a significant improvement in nanohardness (∼8.01 ± 0.32 GPa) and compressive yield strength (∼1284 ± 35 MPa) with keeping a large ductility (>60%), attributed to the uniform distribution of dual-morphology coherent B2 precipitates. The quantitative contributions of different strengthening mechanisms have been estimated in Fe3Cr2NiAl1.1 MPEA. A notable phenomenon has been discovered that Fe3Cr2NiAlx (x = 0.1–0.3) MPEAs showed the serration behavior near the yielding point of compressive stress-strain curves. In the compressive experiments with three different strain rates, as Al content increased, the serration type evolved from type B + C to type B. Serration behavior on stress-strain curves of alloys, impedes the engineering applications of alloys. It is critical to understand serration behavior of MPEAs in phenomenon and theory. This work has broader applicability to understand the effect of Al content on the microstructure and mechanical deformation behavior in MPEAs.

Noise reduction mechanisms for insert-type serrations of the NACA-0012 airfoil

Trailing-edge serrations inspired by owls are capable of reducing broadband noise. In this study, the wall-resolved large-eddy simulations (LES) are carried out on the flow over NACA-0012 airfoil with additional serrated trailing edges. The computations are conducted with the high-order flux reconstruction method on unstructured meshes. Three kinds of serrations with different lengths are studied and compared with the straight trailing-edge case, and all three types of serration achieved a certain degree of noise reduction. Presently, the medium-length serration achieves the best noise reduction effect. The maximum decrease of overall sound pressure level is approximately 2.4 dB, implying that the length of serration has a substantial impact on the noise reduction effect. The serration has no significant effect on the upstream turbulence statistics, but it changes the flow structure near the serration, such as inducing side vortex pairs attached to the serration edges. Moreover, dynamic mode decomposition shows that the pressure structures vary with the serration length. For the most unstable hydrodynamic wave, the spanwise coherence of the mode structure of pressure in the upstream boundary layer is weakened. In addition, serrations can redistribute the dipole sources on the surfaces of airfoil and serrations. The destructive interference is enhanced to some extent, which is favourable for noise reduction. In contrast with LES simulations, the pure dipole analysis shows that the longest serration case seems to be the best. Furthermore, a recently developed noise theory is used to evaluate the influence of serrations on the flow noise sources qualitatively and quantitatively. It is found that the serrations can mitigate noise source intensity near the serration edges but increase the source intensity in the near wake. The combined effect of serration on the dipole source and flow noise source determines the overall noise reduction effect. To conclude, destructive interference plays a primary role in suppressing noise radiation by serrated trailing edges, and the dual effect of flow noise sources should be considered in future serration designs. As the influence of turbulence structure will make it more difficult to find the optimal serration parameters, the position of high-fidelity simulation will become increasingly important.

Portevin-Le Châtelier Effect in a Powder Metallurgy Co-Ni-Based Superalloy.

The Portevin-Le Châtelier (PLC) effect in a powder metallurgy (PM) Co-Ni-based superalloy was systematically investigated via the tensile tests at temperatures ranging from 200 to 600 °C and strain rates at 1.0 × 10−4 to 1.0 × 10−2. Both normal and inverse PLC effects were observed in the PLC regime, and the former appeared in the A and B types at a low temperature, whilst the latter appeared in the C type at an elevated temperature. Both positive and negative strain rate sensitivities (SRS) were shown in PLC regime, and SRS should be derived from same types of serrations. Based on the calculated activation energy, the substitutional atom Mo is considered to take primary responsibility for the PLC effect in present alloy.

Experimental investigation into machinability of hardened AISI D6 steel using newly developed AlTiSiN coated carbide tools under sustainable finish dry hard turning

In the present study, a newly developed AlTiSiN coating material deposited on carbide insert by scalable pulsed power plasma (SPPP) technique is used for machinability investigation of hardened AISI D6 die steel (65HRC) in finish dry turning. Also, the cutting tool is characterized by various diagnostic tests to evaluate the effectiveness of nanocomposite AlTISiN coating material and its cutting performance. A series of machining trials have been performed under varied cutting conditions (feed, depth of cut, speed) to investigate the machinability concerning surface roughness, flank wear, and chip morphology. Further, an approach towards multi-response optimization and predictive modelling for minimization of flank wear and surface roughness have been performed using response surface methodology. Finally, a unique approach has been proposed for economic analysis and sustainability assessment in hard turning. Result shows that the nanostructured AlTiSiN coating developed lower range of tool wear (VB = 0.044–0.076 mm), produced surface finish (Ra) within 0.322–0.905 µm which is approaching the surface quality to that of cylindrical grinding because of minimum friction coefficient, good bonding capability and enhancement in hardness as well as wear resistance of coating material. Statistical analysis reveals that Ra and VB are influenced principally by feed (84.14%) and cutting speed (53.43%), respectively. With the tool life of 34 min, Gilbert's machining economic model calculated the overall machining cost per part of Rs.61.04 in hard turning using coated carbide insert. Chip morphology confirmed the formation of serrated type saw tooth chips. It is established that machining under dry condition provides environment friendliness, techno-economically feasible to improve sustainability.

Mechanical behavior and dynamic strain ageing in Haynes®282 superalloy subjected to accelerated ageing

The microstructure, hardness, impact toughness, and tensile properties of Haynes®282 alloy subjected to accelerated ageing at three temperature and time combinations were studied. Microstructural examination revealed that ageing promotes grain growth, the precipitation and coarsening of various phases and carbides in the matrix and at grain boundaries. While the ageing temperature and time has a minimal effect on the hardness and strength, it significantly deteriorates the ductility and impact strength of the alloy. Elevated temperature tensile behavior reveals that this alloy shows serrated flow due to dynamic strain ageing, and the type of serrations depends on the ageing treatment. In the as-received condition, serrations change from type A to a mixture of type A and type B, and further to type C with increase in strain. Alternately, only type C serrations are present on the flow curves of all the aged alloys. Dislocation interactions with interstitial solutes and substitutional solutes are responsible for the type A and mixture of type A and type B serrations, and type C serrations, respectively. Prolonged ageing also changes the deformation mode from planar slip to wavy slip on the account of γ’ coarsening. Fractographic examination of tensile tested and impact tested specimens indicated that the fracture mechanism transitions from ductile fracture with dimple features to brittle inter-granular features with an increase in the ageing duration. It was inferred that continuous inter-connected carbide network formed during ageing was responsible for reduction in ductility and impact strength.

Effect of Alloying Elements and Microstructure on the Dynamic Strain Aging Behavior of 1.25Cr-0.5Mo and 2.25Cr-1Mo Steels

The effect of alloying elements and microstructure on the dynamic strain aging (DSA) behavior of 1.25Cr-0.5Mo (P11, ASTM 335Gr.P11) and 2.25Cr-1Mo (P22, ASTM 335Gr.P22) steels was investigated. For both steels, different cooling conditions such as air-cooling (AC) and oil-quenching (OQ) were applied. Tensile tests were conducted in the temperature range of 20-450 ℃ and a strain rate in the range of 6 × 10<sup>-5</sup>- 6 × 10<sup>-3</sup> s<sup>-1</sup> for the steels with different cooling conditions. The P11AC steel showed serration behavior over a wider temperature range and exhibited higher ultimate tensile strength (UTS) than for the P22AC steel. This is attributed to the effects of alloying elements (Cr, Mo and Si) due to dissolved C, and the ferrite fraction on mechanical behavior. Meanwhile, the P11AC and P11OQ steels also showed different behaviors for DSA starting temperature, DSA temperature range, and serration type. The AC condition showed higher UTS from the interaction solid solution hardening (ISSH) effect due to substitutional Cr, Mo, and interstitial C elements. The calculated activation energy value (Q) for the P11 steel was around 94-103 kJ/mol<sup>-1</sup>, similar to that of ferritic steels, and it was higher for the P22 steel, with a Q value of 233 kJ/mol<sup>-1</sup> from the ISSH effect.

Deformation mechanism and microstructure evolution of medium-Mn AHSS under various loading conditions

Third-generation advanced high-strength steels possess an exceptional combination of high strength and ductility owing to their high work-hardening rate during deformation. In this study, the mechanical properties and microstructure/texture evolution of medium-Mn steel under various loading conditions (uniaxial tension, in-plane torsion, and equibiaxial tension) were investigated. Interrupted electron back-scattered diffraction and X-ray diffraction characterizations were carried out to track the microstructure and texture evolution of individual phases. Digital image correlation was employed for the in-situ measurement of formation and expansion of deformation bands, i.e., the Lüders and the Portevin-Le Châtelier (PLC) bands. The dynamic strain aging effect in terms of the formation of PLC bands and stress serrations was significantly affected by the loading conditions and stress level. Multiple types of stress serrations were observed in all tested specimens at different deformation stages. The texture evolution of the steel under various deformation modes was further tracked. Ferrite and fresh martensite exhibited the plain texture evolution like most body-centered cubic metals, whereas austenite showed a more complex texture evolution. The martensitic transformation notably decreased the RD||<001> intensity of the austenite; austenite debris was rotated with ferrite grains, while some intact austenite grains self-rotated to a stable orientation, which is unfavorable for martensitic transformation. The obvious intragranular orientation gradient observed in the austenite intact grains implies that considerable deformation occurred in the austenite. Finally, the experimental results indicate that equibiaxial tension primarily promoted the martensitic transformation, and the classical Olson–Cohen model was calibrated to capture the volume fraction evolution of austenite under various stress states.

Experimental and numerical analysis of orthogonal cutting of high strength aluminium alloy Al7075-T6

High strength Aluminum alloys are the key material class for the structural parts of aircraft, aerospace, military, and transportation industries because of their well-known performance, high strength, and light weight. In this present study, the Al7075-T6 tube was machined under orthogonal tool geometry conditions at different parametric combinations of cutting speeds and feed rates to investigate the chip morphology. Orthogonal cutting tests were performed with the high speed steel tool having a back rake angle of 8° and clearance angle of 7°, with varying cutting speeds and feed rates. The metallographic analysis was carried out on the chips obtained from experiments to find out the chip thickness and the type of serrations. Two dimensional finite element analysis was simulated by using ABAQUS/Explicit software. 2D orthogonal plane strain model was created using the Johnson-Cook elastoviscoplastic material model and chip separation criteria were given by the Johnson-Cook damage model. Orthogonal cutting simulations were carried out with the same machining conditions. The orthogonal cutting operation was predicted with numerical simulation and the predicted chip thicknesses were close to experimental chip thickness.