Electron Backscatter Diffraction Results Research Articles

Effect of Magnesium Treatment on Cleanliness, Microstructure, and Magnetic Properties of Fe–80Ni Permalloy

Cleanliness and microstructure significantly impact the magnetic properties of soft magnetic materials. This study investigates the impact of Mg treatment on the cleanliness, microstructure, and magnetic properties of Fe–80Ni alloy. The content of Mg ranges from 0% to 0.034%. The O and S contents can be reduced to 0.0006% and 0.0011%, respectively, when the content of Mg is 0.027%, and the number of inclusions is reduced. Simultaneously, the primary inclusions are modified to Mg‐containing inclusions. Based on electron backscattered diffraction results, Mg treatment can refine the deformed grain and enhance grain boundary energy after cold rolling. In addition, the grains exhibit enhanced growth after annealing with Mg treatment. Due to the improvement of cleanliness and microstructure, the magnetic properties of Fe–80Ni alloy are enhanced with Mg treatment. With Mg treatment, the coercivity of alloys is reduced, and maximum magnetic susceptibility (χmax) increases to 0.3247 with Mg treatment, while that is 0.1938 without Mg treatment.

Influence mechanism of microstructure variation on mechanical properties of laser melting deposition Ti–6Al–4V alloy under electroshocking treatment

In this work, the electroshocking treatment (EST) was applied on the Ti–6Al–4V alloys prepared by laser melting deposition (LMD), and the evolutions of microstructure and mechanical property were investigated. The results indicated that the size of columnar grains in LMD Ti–6Al–4V was reduced after EST, and the α refinement was obvious. The basket weave microstructure existed due to the effect of EST. The results of electron backscatter diffraction (EBSD) showed that EST could reduce the orientation concentration and weaken the texture. The texture in Ti–6Al–4V was formed during LMD, and it became uniform and weak after EST. On the mechanical properties, the microhardness of specimen increased after EST with 0.04 s, and the yield strength changed little and the strain increased more obviously because of the microregion phase transition. The compression fracture morphology revealed that the fracture mode of LMD Ti–6Al–4V changed from the brittle fracture to ductile fracture because of the microstructure variation. Based on above results, it demonstrates that EST is a new exploration method to manipulate the microstructure of LMD titanium alloys and modify the comprehensive mechanical properties of LMD titanium alloys.

Effect of rotational speed and feed rate on microstructure and mechanical properties of 6061 aluminum alloy manufactured by additive friction stir deposition

Additive friction stir deposition (AFSD) is attractive for its ability to create freeform and fully dense structures without melting and solidification. Hence, additive friction stir deposition is an alternative to fusion-based additive manufacturing technology. In this study, the influence of the AFSD parameter (i.e., rotational speed and feed rate) on the mechanical properties and microstructure of 6061 aluminum alloy is investigated. The as-deposited 6061 aluminum alloy exhibits a relatively homogeneous microstructure with extensive equiaxed grains. Compared to the feedstock material, the ultimate tensile strength of the as-deposited 6061 aluminum alloy decreased to 65% from 320 to 210 MPa. The results of electron backscatter diffraction indicate that continuous dynamic recrystallization occurs during the AFSD process. Furthermore, it is evidence that the grain size and ultimate tensile strength are positively correlated with feed rate and rotational speed, whereas the elongation at break decreases with the increase in feed rate and rotational speed.

A microstructure-based multiscale approach to predict the formability of multiphase steels

A multiscale approach was proposed to predict the macroscopic forming limit of Q&P980 steel. The microstructure-based simulation was implemented in the microscopic simulation to obtain the macroscopic stress-strain curve. The representative volume element (RVE) was established using the data extracted from the characterised results of electron back-scattered diffraction (EBSD). The microscopic constitutive model of each constituent phase was determined based on a new method. The acquired macroscopic stress-strain curve was extrapolated using the modified Power-Law (MPL) strain hardening model. In the macroscopic simulation, the Nakajima and Marciniak-Kuczynski (M-K) simulations were combined to obtain the macroscopic forming limit only based on the macroscopic stress-strain curve. The microscopic and macroscopic simulations show good agreement with the experiment results, verifying the multiscale approach's accuracy. This study provides a solution for the direct connection between the microstructure and macroscopic forming limit.

A new measure to enhance the heat-resistant (4TiC + 5AlN)/Al composite by multi-scale Fe/Mn enrichment effect

Developing high-strength Al-based alloys that can operate at 250 °C and above remains a challenge. In this study, a heat-resistant and high-strength (4TiC + 5AlN)/Al–Fe–Mn composite is designed using the liquid–solid reaction and hot extrusion. The strengthening phases, including sub-micron TiC, micron Al3(Fe, Mn), nano-sized AlN, and nano-sized Al3(Fe, Mn), in which the in–situ AlN particles are distributed in the matrix as networks, exhibit an attractive strengthening effect. Based on the results of electron backscatter diffraction, the extruded (4TiC + 5AlN)/Al–Fe–Mn composite prefers to form fiber texture in the longitudinal and cross-section:<111>Al//ED. And the average grain size of (4TiC + 5AlN)/Al–0.3Fe–0.1Mn composite is 0.69 µm. The ultimate tensile strength of the (4TiC + 5AlN)/Al–Fe–Mn composite is as high as 215 MPa at 350 °C. And the high-temperature elongation of the (4TiC + 5AlN)/Al–Fe–Mn composite is maintained while increasing the high-temperature strength. The improved performance of the (4TiC + 5AlN)/All–Fe–Mn is attributed to the synergistic effect of the multi-scale Al3(Fe, Mn) phases and particles. Furthermore, the formed micrometer Al3(Fe, Mn) phases are used to regulate the distribution of the TiC and AlN particles. The nano-Al3(Fe, Mn) dispersoids that precipitated during the homogenization can enhance the high-temperature deformation resistance of the matrix. In particular, the Fe and Mn atoms tend to aggregate at the TiC/Al interface, effectively modifying the interfaces between ex-situ TiC particles and the Al matrix. The modified interfaces of TiC/Al are beneficial to load transfer strengthening. The strengthening mechanisms of the (4TiC + 5AlN)/Al–Fe–Mn composite have been analyzed in detail, and the main strength–increasing mechanisms are calculated from the microstructural data. This work may provide an important approach to preparing heat-resistant Al matrix composites with strength-ductility matching.

Dynamic vapor and keyhole behavior, and equiaxed dendrite formation in blue laser processing of copper

A coupled Cu vapor and keyhole numerical model including a simple virtual mesh refinement method was developed to investigated the Cu vapor and keyhole behavior in blue laser processing of a copper material. Electron backscatter diffraction (EBSD) was adopted to measure the crystal structure of the fusion zone. The Cu vapor mainly flowed upwards above the keyhole, while some downward flows were observed inside the keyhole. The recoil force and Marangoni stress caused the melt at the keyhole wall to flow downwards, and the Marangoni stress caused the melt at the pool edge to flow outwards. Owing to the multiple reflections and high absorption rate, the total blue laser energy efficiency can be as high as 83.1%. The EBSD, numerical and theoretical results indicated that the blue laser favored the fine equiaxed dendrite formation in the center of the fusion zone, which was attributed to the higher value of the cooling rate G × R, where G is the temperature gradient and R is the solidification rate, and the lower value of G/R at this location, unlike the previously studied infrared laser processing case.

Indentation Plastometry for Study of Anisotropy and Inhomogeneity in Maraging Steel Produced by Laser Powder Bed Fusion

This work concerns the use of profilometry‐based indentation plastometry (PIP) to obtain mechanical property information for maraging steel samples produced via an additive manufacturing route (laser powder bed fusion). Bars are produced in both “horizontal” (all material close to the build plate) and “vertical” (progressively increasing distance from the build plate) configurations. Samples are mechanically tested in both as‐built and age‐hardened conditions. Stress–strain curves from uniaxial testing (tensile and compressive) are compared with those from PIP testing. Tensile test data suggest significant anisotropy, with the horizontal direction harder than the vertical direction. However, systematic compressive tests, allowing curves to be obtained for both build and transverse directions in various locations, indicate that there is no anisotropy anywhere in these materials. This is consistent with electron backscattered diffraction results, indicating that there is no significant texture in these materials. It is also consistent with the outcomes of PIP testing, which can detect anisotropy with high sensitivity. Furthermore, both PIP testing and compression testing results indicate that the changing growth conditions at different distances from the build plate can lead to strength variations. It seems likely that what has previously been interpreted as anisotropy in the tensile response is in fact due to inhomogeneity of this type.

Characterization of Properties of Laser Powder Bed Fusion Three-Dimensional-Printed Inconel 718 for Centrifugal Turbomachinery Applications

AbstractThis paper presents the results of a comprehensive effort to characterize the properties of Inconel 718 produced by a form of laser powder bed fusion (LPBF) additive manufacturing (AM) or three-dimensional (3D)-printing, subsequently subjected to hot isostatic pressing (HIP) and heat treatment according to standards F3055-14a and AMS 5663, respectively. Material property data, while broadly available for traditional Inconel 718 presentations (e.g., forgings or castings) is currently lacking for the 3D-printed material. It is expected that while limited in size, the experimental data sets presented provide sufficient information to glean the capability of LPBF Inconel 718. These include: (1) chemical composition, electron backscatter diffraction (EBSD), and X-ray energy dispersive spectroscopy (XEDS) characterization of 3D-printed material structure; (2) tensile properties—0.2% yield stress, ultimate stress, modulus of elasticity, and elongation to failure—based on 108 samples, as functions of temperature and sample print orientation; (3) creep rupture data including the Larson-Miller parameter, based on 21 samples; and (4) high cycle fatigue data based on 21 samples as a function of temperature. Results are compared to available standards and/or data for forged, cast, and other AM Inconel 718. A key observation of this study, based on the EBSD results, is that while the material appears to approach full recrystallization following heat treatment, there is a detectable fraction of the material that does not fully recrystallize, resulting in a material with mechanical properties (e.g., yield stress and creep rupture) measurably lower than those of forgings, but higher than those of castings.

Micro-nano secondary phase greatly increases the plasticity of titanium-zirconium-molybdenum alloy

Improving ductility without sacrificing strength remains challenging for brittle molybdenum and its alloys. Titanium‑zirconium‑molybdenum alloy with the micro-nano-scale secondary phases (MN-TZM) was prepared using titanium sulfate, zirconium nitrate, fructose, and molybdenum powder as raw materials. The elongation at failure of the MN-TZM alloy was increased by 2.3 times to 15.1% without sacrificing strength. The fracture of the MN-TZM alloy exhibited cleavage and ductile tearing characteristics. Transmission electron microscopy and electron backscatter diffraction results indicate that dislocations can slip along the (110) plane at different strains, bypassing or even passing through the micro-nano-scale secondary phase (MN-SP) in MN-TZM alloys. The stacking faults and dislocation junctions of the MN-TZM alloy substructure avoid stress concentration and enhance the deformation ability. This study provides theoretical guidance for the industrial production of high-performance secondary-phase dispersion-strengthened structural materials, linking process-structure-properties relationships.

Compressive properties of a severely deformed fine-grained Mg−6Gd−3Y alloy

An extruded Mg−6Gd−3Y alloy was processed by 6 passes of simple shear extrusion (SSE) at 553 K to refine the microstructure. The microstructural studies were performed through electron back-scattered diffraction (EBSD) and also transmission electron microscopy (TEM) to investigate the microstructural features which emerged after SSE. It was revealed the SSE-processed alloy had a duplex microstructure containing both fine dynamically recrystallized (DRX) grains and some large deformed grains. A relatively high fraction of low angle grain boundaries (LAGBs), induced within the un-DRXed deformed grains, was identified by EBSD results. TEM studies revealed the formation of round Mg5Gd-type nano-particles through dynamic precipitation only in the DRXed regions of microstructure in the SSE-processed alloy. Compressive mechanical properties and strain hardening behavior of the alloys were assessed by compression testing of both alloys at room temperature. SSE processing resulted in enhanced yield stress and reduced ductility. Both the extruded and SSE-processed alloys exhibited a three-stage strain hardening behavior with a much more pronounced stage II of hardening in the latter one. According to the mechanical properties results, there was a noticeable difference in the strain hardening rate and also dislocation storage rate of the extruded and SSE-processed alloys. This discernible strain hardening behavior of the two alloys was attributed to the formation of fine DRXed grains, dynamic precipitation of nano-sized Mg5Gd particles, and induction of LAGBs, which emerged after SSE.

High ductility CrCoNi medium entropy alloy prepared by liquid nitrogen temperature rolling and short time annealing at moderate temperature

As-cast CrCoNi Medium Entropy Alloy (as-casted MEA) was obtained by vacuum arc melting. The as-casted MEA was rolled 3 times at the temperature of liquid nitrogen (77 K), the sum of the total deformation was 50%. Then, the rolled CrCoNi Medium Entropy Alloy (as-rolled MEA) were annealed with different parameters, the annealing parameters were 923 K/30min, 973 K/30min and 1073 K/30min respectively. The experimental samples were characterized by uniaxial tensile test at room temperature, electron back scatter diffraction (EBSD) and transmission electron microscopy (TEM). The tensile test results showed the CrCoNi MEA was deformed by Liquid Nitrogen rolling, the tensile strength increased from 421 MPa to 1312 MPa, but the elongation was only 7.4%. The as-rolled MEA annealed at moderate temperature and short time, the ductility of the CrCoNi was improved significantly. When the as-rolled MEA annealed at 1073 K/30 min, the elongation of CrCoNi increased to 65.3%, while the tensile strength maintained 800 MPa. The EBSD and TEM results showed that the CrCoNi MEA was deformed by Liquid Nitrogen rolling, there were a lot of high density dislocation regions in the alloy. At the same time, a large number of bunches of stacking faults (SFs), intersected SFs and deformation twins (DT) were found in the rolled MEA. The EBSD and TEM results also showed that when the CrCoNi MEA was annealed, a large number of type B and type C annealing twins and 9 R structures were found in the alloy. The growth of annealing twins were achieved by the mechanism of grain boundary migration caused by stacking faults annexation. After annealing, the transformation of FCC→9 R structure was occurred, and the 9 R structure caused more boundary nucleation of annealing twins. The annealing twins and 9 R structure played a key role in improving the ductility of the annealed CrCoNi MEA. Adopt the technology of moderate temperature combining short time annealing process, can effectively control the properties of CrCoNi MEA.

Effect of Shot Peening Strengths on Microstructure and Mechanical Properties of 316L Stainless Steel Prepared by 3D Printing

Herein, the influence of shot peening (SP) on the microstructure and mechanical properties of 3D printed 316L stainless steel is studied by optical microscopy (OM), electron backscattered diffraction (EBSD), and mechanical properties testing. The changes in microstructure and mechanical properties of 316L stainless steel by 3D printing under different SP strengths are explored, which are drawn as follows: 1) the microstructure of 3D‐printed 316L stainless steel is greatly refined, and the thickness of ultrafine microstructure in the surface layer increases from 0 to 112.5 μm with the increase in peening strengths from 0 to 0.4 MPa; 2) with the increase of peening strengths from 0 to 0.4 MPa, the hardness increases from 236 to 518 HV, and yield strength increases from 547.3 to 740.7 MPa; and 3) based on the EBSD results, the enhanced hardness and yield strength are caused by refinement hardening and dislocation hardening for the SP samples. In addition, it should be noted that the SP decreases the elongation of 3D‐printed 316L stainless steel up to 9%, and makes the ultimate tensile strength reach the maximum value of 871.2 MPa at 0.2 MPa SP strength.

Statistical analysis and recovery behaviors of dislocations in cold‐rolled and annealed reactor pressure vessel steels

AbstractThe statistical analysis and recovery behavior of dislocations in cold‐rolled and annealed reactor pressure vessel steels with a thickness reduction of 50 % were investigated by using x‐ray diffraction and electron backscattered diffraction analysis in this study. A new modified Kubin &amp; Mortensen's method was proposed to evaluate the geometrically necessary dislocation density, and this method could effectively improve the accuracy of geometrically necessary dislocation evaluation by eliminating the effect of step size and measurement noises. Comparison analysis between modified Williamson‐Hall and modified Kubin &amp; Mortensen's methods was also performed in this study, which shows different recovery behavior of dislocations. The electron backscattered diffraction results show that geometrically necessary dislocation density remained unchangeable after annealing treatment below and at 550 °C, and it occurred to decrease above 550 °C due to the occurrence of recrystallization. However, dislocations started to migrate and annihilate at 340 °C according to x‐ray diffraction results. A possible explanation is a difference in the effect of pairwise dislocation annihilation on statistically stored dislocations and geometrically necessary dislocations.

The Effect of Laser Shock Peening on Back Stress of Additively Manufactured Stainless Steel Parts

Abstract This work studies the use of laser shock peening (LSP) to improve back stress in additively manufactured (AM) 316L parts. Unusual hardening behavior in AM metal due to tortuous microstructure and strong texture poses additional design challenges. Anisotropic mechanical behavior complicates application for mechanical design because 3D printed parts will behave differently than traditionally manufactured parts under the same loading conditions. The prevalence of back-stress hardening or the Bauschinger effect causes reduced fatigue life under random loading and dissipates beneficial compressive residual stresses that prevent crack propagation. LSP is known to improve fatigue life by inducing compressive residual stress and has been applied with promising results to AM metal parts. It is here demonstrated that LSP may also be used as a tool for mitigating tensile back-stress hardening in AM parts, thereby reducing anisotropic hardening behavior and improving design use. It is also shown that the method of application of LSP to additively manufactured parts is key for achieving effective back-stress reduction. Back stress is extracted from additively manufactured dog bone samples built in both XY and XZ directions using hysteresis tensile. Both LSPed and as-built conditions are tested and compared, showing that LSPed samples exhibit a significant reduction to back stress when the laser processing is applied to the sample along the build direction. Electron backscatter diffraction (EBSD) performed under these conditions elucidates how grain morphologies and texture contribute to the observed improvement. Crystal plasticity finite element (CPFE) modeling develops insights as to the mechanisms by which this reduction is achieved in comparison with EBSD results. In particular, the difference in plastic behavior across build orientations of identified crystal planes and grain families are shown to impact the degree of LSP-induced back-stress reduction that is sustained through tensile loading.

Anisotropic tensile behavior of laser powder-bed fusion made Ti5553 parts

Directional heating during metal additive manufacturing promotes the growth of a columnar-grained microstructure along the building direction with a preferred crystal orientation, which results in anisotropy of properties. In this work, the anisotropy of laser powder bed fused Ti-5553 metastable β titanium alloy components are investigated. Samples printed in the normal (vertically printed), and parallel (horizontally printed) orientations to the building direction were subjected to quasi-static uniaxial tensile tests. In comparison, samples printed parallel to the building direction exhibit a significantly higher ultimate strength of 846 ± 6 MPa, whereas the samples printed normal to the building direction reached 780 ± 10 MPa. Fracture initiation and propagation were investigated using interrupted tensile testing. The fracture path of partially fractured specimens reveals the development of slip bands oriented at a 45 ± 5° angle with respect to the loading direction, which promoted fracture by coalescence of aligned pores. Electron backscatter diffraction results indicate that the grain boundaries act as favorable nucleation sites for fracture initiation, particularly when they align perpendicular to the loading direction. Conversely, fracture in samples printed parallel to the building direction was predominantly transgranular, which is expected to be a major contributing factor to the higher strength observed.

Significance of underwater friction stir welding on the weld integrity of thin sheets of aluminum (AA1050-O) and brass (CuZn34) joints

Classical friction stir welding (C-FSW), because of its solid-state joining nature, offers several benefits over traditional fusion welding for joining dissimilar materials. C-FSW conducted in open air, are affected by several weld flaws and thick Intermetallic Compounds (IMCs) that reduce the weld joint quality. In this study, FSW of thin sheets of aluminum alloy (AA1050-O) and brass (CuZn34) in lap joint configuration was performed in air and underwater. The main objective of this study was to investigate the feasibility of underwater-FSW (UW-FSW) for obtaining aluminum and brass (Al-Brass) joints at different values of shoulder plunge depth (SPD) and tool rotational speed (N). To determine the effect of welding temperature at different values of SPD and N on the formation of weld joints, K-type thermocouples were used. Underwater welding reduced the welding temperature and thermal cycle time. The optical images of C-FSW joints revealed the presence of kissing bonds, wavy patterns, cracks, tunnels, and void defects. In UW-FSW, the faster cooling rate significantly reduced these weld flaws. Electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) were used for the microstructural characterization. EBSD and TEM results show fine microstructure and precipitates in UW-FSW specimens. The X-ray diffraction results demonstrated that the weld joint interface primarily consisted of Al-Cu & Cu-Zn IMCs in the form of Al4Cu9, Al2Cu, AlCu3, AlCu4, CuZn5, and Cu5Zn8. The amount of IMCs was less in the joints produced by UW-FSW. The obtained results were used to understand the variation in the weld strength of C-FSW and UW-FSW joints at different values of SPD and N. To further evaluate the interface of the Al-Brass weld joint, energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM) were employed. EDS confirmed the presence of brass fragments in the stirred zone of aluminum substrate. TEM and SEM images illustrated fine precipitates and formation of thin IMC layers in UW-FSW. The tensile test result shows that the UW-FSW remarkably improved the joint strength. The percentage increase in the joint tensile strength for UW-FSW was found 42%, 30% and 50% higher than C-FSW for lower, medium and high heat input welding conditions. The lower heat input in UW-FSW significantly suppressed the formation of weld flaws and IMCs, which collectively improved the tensile strength of the weld joint.

Microstructure and Solute Segregation around the Melt-Pool Boundary of Orientation-Controlled 316L Austenitic Stainless Steel Produced by Laser Powder Bed Fusion.

For this article, we studied the microstructure and solute segregation seen around the melt pool boundary of orientation-controlled 316L austenitic stainless steel produced by laser powder bed fusion, using transmission electron microscopy and energy-dispersive x-ray spectroscopy. We found that the solidification cellular microstructures could be visualized with the aid of solute segregation (Cr and Mo) during solidification. Mn-Si-O inclusions (10-15 nm in diameter) were distributed along the lamellar boundaries, as well as in the dislocation cell walls. It is believed that the grain growth of the inclusions can be effectively suppressed by rapid quenching during the laser powder-bed fusion process. A thin region without cellular microstructures was observed at the melt-pool boundary. The cellular spacing widened near the bottom of the melt-pool boundary, owing to the decrease in the cooling rate. Atomic-structure analysis at the lamellar boundary by high-resolution transmission electron microscopy revealed a local interfacial structure, which is complementary to the results of electron back-scatter diffraction.

Electrically assisted manufacturing of microchannels with enhanced filling quality and microstructural performance for thermal management

The printed circuit heat exchanger (PCHE) with arrayed microchannel structures is ideal for the extreme thermal management of hypersonic flight vehicles. Electrically assisted manufacturing (EAM) has a remarkable predominance in fabricating microchannels on sheet metals. By conducting EA micro-embossing experiments at current densities of 20, 25, and 40 A/mm2, respectively, the filling behavior and microstructural evolution of SUS304 sheets under the influence of current were elucidated in this study. The results indicated that a higher current density shortens the initial extrusion stage's duration and facilitates the material flow transition to the filling stage. Moreover, the current can simultaneously enhance the filling height and profile quality by minimizing the stress and stress differential in the deformation region of the filling section. The results of electron backscatter diffraction (EBSD) demonstrated that recrystallization occurs due to the synergistic effect of deformation and current. The degree of recrystallization in different regions of the filling section has a huge discrepancy. The region beneath the tooth exhibits considerable recrystallization and contains abundant refined grains. At the current density of 20 A/mm2, a number of dislocations accumulated in the deformed grains, and the filling section mainly consisted of 〈1 1 1〉 fiber texture and 〈1 0 1〉 deformation texture. In the process of continual dynamic recovery and recrystallization, dislocation packing relives at the current density of 40 A/mm2, which is one reason for the increase in filling quality. The 〈1 1 1〉 texture and 〈1 0 1〉 deformation texture are weakened and rotate as the forming temperature rises. Additionally, the 〈1 0 1〉 texture transforms into a 〈0 0 1〉 recrystallized texture. The diminished 〈1 0 1〉 deformation texture, the rotated 〈1 1 1〉 texture, and the appearance of 〈0 0 1〉 recrystallized texture enhance the homogenous strain distribution of the filling section, which is an additional explanation for the improvement of filling quality at high-density current. Based on the above results, a high-performance PCHE prototype with a pressure bearing capacity of 23 MPa and a heat transfer coefficient of 22 kW/(m2·K) was manufactured by EAM, confirming that the EAM technique is capable of achieving high-quality and eco-friendly fabrication of the enhanced microchannels.

Current-carrying tribological properties of an elastic roll ring under different currents

A novel rotating conductive joint that comprises an inner raceway, outer raceway, and a roll ring is proposed in this study. The tribological and conductive properties of the rolling rings were studied under current conditions of 0–20 A. The current density of the rolling contact reached 419 A/mm2 when transmitted at 20 A. However, a high current could result in a high-friction coefficient and severe wear. The results of optical microscopy and electron back-scattered diffraction showed that the grain boundary was partially annihilated, and the stress decreased in the wear area under 10 and 20 A. On the wear surface, the current-carrying friction caused the hardening, and the electroplasticity caused softening. The surface hardness of the wear area was the result of competition between hardening and softening, which reached its highest value at 5 A.

Crystal plasticity modeling on the selective laser melted AlSi10Mg alloy

Additive manufacturing (AM) has been developing into a revolutionary technique, in which parts are created by additive processing as opposed to the conventional subtractive manners. AM components possess the characterization of special microstructure and porosity. In this paper, a computational method is developed to investigate the mechanical property of selectively laser melted (SLM) AlSi10Mg alloy. The DREAM.3D software is utilized to generate a polycrystal model based on electron backscatter diffraction (EBSD) results. The investigated alloy shows a weak texture that the grain preferential grows along the <100> orientation. The real defect geometries are reconstructed from X-ray Computed Tomography (XCT) experimental slices and embedded into a representative volume element (RVE) model. Furthermore, a crystal plasticity (CP) model integrated fast Fourier transform method (FFT) in Düsseldorf Advanced Material Simulation Kit (DAMASK) package is implemented to simulate the mechanical response for the RVE model. The effect of porosity on tensile strength is studied, and result shows the defects degrade tensile strength.