Anisotropic Mechanical Properties Research Articles

Drop cushioning dynamic effects of corrugated cardboard with effective anisotropic constitutive model

PurposeThe primary objective of this study is characterizing the anisotropic mechanical properties of corrugated cardboard and simultaneously simulating its drop cushioning dynamic effects under various drop conditions.Design/methodology/approachStatic and dynamic tests were conducted on corrugated cardboard to obtain adequate experimental data in different directions. An effective anisotropic constitutive model is introduced by developing the honeycomb materials model in ANSYS LS-Dyna, and an effective approach is established toward effectively determining the material parameters from the test data obtained. The model is validated by comparing simulation results with experimental data from five drop conditions, including bottom drop, front drop, side drop, 30° side drop and edge drop. Additionally, simulations are conducted to study the cushioning performance of the packaging by dropping the corrugated cardboard at different heights.FindingsThe study establishes a fast and effective approach to simulating the drop cushioning performance of corrugated cardboard under various drop conditions, which demonstrates good agreement with experimental data.Originality/valueThis approach is of value for packaging protection and provides guidance for stacking of packaging during transportation.

Anisotropic Mechanical Properties of Al-Mg-Sc-Zr Alloy Fabricated by Selective Laser Melting

Anisotropic Mechanical Properties of Al-Mg-Sc-Zr Alloy Fabricated by Selective Laser Melting

Effects of cellular crossing paths on mechanical properties of 3D printed continuous fiber reinforced biocomposite honeycomb structures

3D printing continuous fiber reinforced composite (CFRC) has the advantages of manufacturing complex shapes and short production cycles. Due to the anisotropic mechanical properties of continuous fibers, the printing path of the fibers determines the properties of the printed CFRCs. In this paper, a series of novel cellular crossing paths were proposed to print continuous ramie fiber reinforced biocomposite honeycomb structures (CFHSs). The compression, bending, and tensile tests were performed to analyze the effects of cellular crossing paths on the mechanical properties of CFHSs. An assessment method was presented for analyzing the comprehensive mechanical properties of CFHSs printed by different printing paths. The results showed that the CFHSs printed by no-crossing path (Path-1), single-crossing path (Path-3), and double-crossing path (Path-4) exhibited better compression, bending, and tensile properties, respectively. In addition, the samples printed by Path-3 were the most outstanding in the assessments of comprehensive mechanical properties, the comprehensive performance assessment score was 1.5 times that of the single-crossing path (Path-2, minimum score). Thus, an appropriate cellular crossing path could be selected according to the structural load-bearing state, thereby providing higher mechanical properties.

Fiber Reinforcement of 3D Printed Concrete by Material Extrusion Toolpaths Aligned to Principal Stress Trajectories

Additive manufacturing of cementitious materials is a rapidly growing branch of manufacturing both in research and industry, particularly the variant of material deposition by extrusion. This process results in a strong anisotropy in mechanical properties, owing largely to the interfaces between adjacent filaments. This anisotropy is even more pronounced when fiber reinforced mortars or continuous entrained reinforcement components such as cables are used. To exploit orientation-dependent performance, the print path can be designed to align with the principal (tensile) stress trajectories. However, obtaining an appropriate print path based on this concept poses several challenges, related to the filling of intermediate spaces between two trajectories. In this paper, an approach for planning such a robot toolpath is presented, elaborated, and illustrated by means of a case study on a well-known reference case. The main features of the tool planning method are the relaxation of the offset width, the avoidance of toolpaths with acute angles by intersecting offset curves, and a continuous toolpath.

Liquid crystalline composite hydrogels with large pH-triggered anisotropic swelling for embolotherapy

Inspired by the anisotropic structure of biological tissues, anisotropic hydrogels have been developed using various nanofillers, however, it remains a big challenge to synthesize hydrogels with large swelling anisotropy. Herein a single molecule filler, α-helical polypeptide, instead of nanoscale fillers, was used to synthesize anisotropic hydrogels. First nematic liquid crystal of poly(γ-benzyl l-glutamate) (PBLG) was prepared by shearing and stabilized by embedding in a crosslinked polymer matrix. The resulting PBLG composite gels were then converted to poly(L-glutamic acid) (PLGA) composite gels by debenzylation. The rigid rod-like structure of α-helical PBLG chains makes them easy to be orientated. The pH-sensitivity of PLGA makes the resulting composite gels pH-sensitive without the need to couple with a stimuli-responsive hydrogel matrix. In response to pH change PLGA composite gels swell anisotropically with a much larger swelling degree in the radial direction than in the axial direction. The swelling anisotropy (3.43) is much higher than most anisotropic hydrogels, particularly the stimuli-responsive ones reported previously. The composite gel also exhibits anisotropic mechanical properties with a larger Young's modulus in the axial direction than that in the radial direction. Preliminary test demonstrated that the composite gels have potential in embolotherapy thanks to its large pH-triggered anisotropic swelling. Statement of SignificanceAnisotropic hydrogels have important biomedical applications. Introduction of oriented nanofillers has been demonstrated a popular and versatile method for their synthesis, however, it remains a big challenge to achieve large swelling anisotropy. Herein a single molecule filler, α-helical polypeptide, instead of nanoscale fillers, was used to synthesize anisotropic hydrogels. This filler can be easily oriented by shearing. More importantly, as single molecule filler, it can constrain the swelling of hydrogel matrix more effectively. Using this filler, a pH-sensitive hydrogel with large swelling anisotropy (3.43) was successfully synthesized. Thanks to its large pH-triggered anisotropic swelling the hydrogel was successfully used as embolic agent to occlude vessels.

Interfacial performance and build orientation of 3D‐printed poly(ether‐ketone‐ketone) reinforced by continuous carbon fiber

AbstractContinuous fiber reinforced thermoplastic composites (CFRTPCs) prepared by fused deposition modeling (FDM) have gained great attention for the benefit of preparing products without molds. However, unexpected debonding and defects are derived from insufficient impregnation between fiber and matrix in 3D‐printed samples, resulting in weak interfacial performance. In this work, a polyetherimide (PEI) sizing agent was used to improve the fiber‐matrix interfaces, and the interlaminar shear strength (ILSS) of the continuous carbon fiber reinforced poly(ether‐ketone‐ketone) composites was increased to 27.1 MPa, 12.4% higher than that of unmodified composite. Meanwhile, the performance of CFRTPCs is affected by process parameters in FDM. Build orientation of FDM was discussed and PEI weakened the anisotropy of samples' mechanical properties because the performance variation caused by build orientation decreased from 86.8% to 65.2%, which may be beneficial for the forming freedom of in situ impregnated FDM. The addition of PEI makes sense to apply in situ impregnated FDM in high‐tech fields.Highlights CCF/PEKK composites were prepared by in situ impregnated FDM. ILSS of flat‐oriented CCF/PEKK was 86.8% higher than that of on‐edge. 5 wt% PEI sizing agent promoted adhesion of CCF and PEKK to obtain the best mechanical properties. PEI weakened the anisotropy of samples' mechanical properties, which was conducive to forming freedom.

Highly compliant biomimetic scaffolds for small diameter tissue-engineered vascular grafts (TEVGs) produced via melt electrowriting (MEW)

Biofabrication approaches toward the development of tissue-engineered vascular grafts (TEVGs) have been widely investigated. However, successful translation has been limited to large diameter applications, with small diameter grafts frequently failing due to poor mechanical performance, in particular mismatched radial compliance. Herein, melt electrowriting (MEW) of poly(ϵ-caprolactone) has enabled the manufacture of highly porous, biocompatible microfibre scaffolds with physiological anisotropic mechanical properties, as substrates for the biofabrication of small diameter TEVGs. Highly reproducible scaffolds with internal diameter of 4.0 mm were designed with 500 and 250 µm pore sizes, demonstrating minimal deviation of less than 4% from the intended architecture, with consistent fibre diameter of 15 ± 2 µm across groups. Scaffolds were designed with straight or sinusoidal circumferential microfibre architecture respectively, to investigate the influence of biomimetic fibre straightening on radial compliance. The results demonstrate that scaffolds with wave-like circumferential microfibre laydown patterns mimicking the architectural arrangement of collagen fibres in arteries, exhibit physiological compliance (12.9 ± 0.6% per 100 mmHg), while equivalent control geometries with straight fibres exhibit significantly reduced compliance (5.5 ± 0.1% per 100 mmHg). Further mechanical characterisation revealed the sinusoidal scaffolds designed with 250 µm pores exhibited physiologically relevant burst pressures of 1078 ± 236 mmHg, compared to 631 ± 105 mmHg for corresponding 500 µm controls. Similar trends were observed for strength and failure, indicating enhanced mechanical performance of scaffolds with reduced pore spacing. Preliminary in vitro culture of human mesenchymal stem cells validated the MEW scaffolds as suitable substrates for cellular growth and proliferation, with high cell viability (>90%) and coverage (>85%), with subsequent seeding of vascular endothelial cells indicating successful attachment and preliminary endothelialisation of tissue-cultured constructs. These findings support further investigation into long-term tissue culture methodologies for enhanced production of vascular extracellular matrix components, toward the development of the next generation of small diameter TEVGs.

Manipulating mechanical properties of PEG-based hydrogel nanocomposite: A potential versatile bio-adhesive for the suture-less repair of tissue

Multifunctional bio-adhesives with tunable mechanical properties are obtained by controlling the orientation of anisotropic particles in a blend of fast-curing hydrogel with an imposed capillary flow. The suspensions' microstructural evolution was monitored by the small-angle light scattering (SALS) method during flow up to the critical Péclet number (Pe≈1) necessary for particle orientation and hydrogel crosslinking. The multifunctional bio-adhesives were obtained by combining flow and UV light exposure for rapid photo-curing of PEGDA medium and freezing titania rods' ordered microstructures. Blending the low- and high-molecular weight of PEGDA polymer improved the mechanical properties of the final hydrogel. All the hydrogel samples were non-cytotoxic up to 72 h after cell culturing. The system shows rapid blood hemostasis and promotes adhesive and cohesive strength matching targeted tissue properties with an applicating methodology compatible with surgical conditions. The developed SALS approach to optimize nanoparticles’ microstructures in bio-adhesive applies to virtually any optically transparent nanocomposite and any type of anisotropic nanoparticles. As such, this method enables rational design of bio-adhesives with enhanced anisotropic mechanical properties which can be tailored to potentially any type of tissue.

Experimental study on the size effect and anisotropy in mechanical properties of fractured rock mass based on 3D printing

The size effect and anisotropy of fractured rock mass mechanical parameters are difficult problems to solve in the field of engineering. This study taken full advantage of sand 3D printing technology to batch-reproduce complex structures and prepare rock-like specimens with different sizes and rotation directions. The size effect and anisotropy of the fractured rock mass were investigated. Digital image correlation was used to conduct noncontact full-field observations of the specimen. The results showed that the sand 3D printing specimens have the advantages of high precision and brittleness and can reproduce the deformations and failure processes of natural rock. The compressive strength and failure mode of the fractured rock have significant size effect characteristics. Assessing the size effect on the compressive strength of the specimen, 100 × 100 mm is the mechanical representative elementary volume (mREV) scale. The compressive strength and failure mode of the fractured rock under the mREV scale show obvious anisotropy. Based on the size effect of fracture density, 80 × 80 mm was identified as the geometric representative elementary volume (gREV) scale. The gREV scale was smaller than and close to the mREV scale was found. In addition, the differentiation rate of standard deviation (DRSD) is defined to provide information on the dispersion of the strain field and the precursor information of crack initiation during the deformation and fracture of the rock mass. This study provides a new method for laboratory experimental studies on the size effect and anisotropy of complex fractured rock masses from the perspective of 3D printing.

Mechanical behavior of austenitic stainless steels produced by wire arc additive manufacturing

Wire arc additive manufacturing (WAAM) is an innovative technology with the potential to drive the transformation and upgrading of metallic manufacturing industry and construction sector. The advantages of WAAM technology in rapid manufacturing, design freedom, and energy saving have attracted attentions in the construction field. This research study focuses on investigating the microstructural and mechanical behavior of austenitic stainless steels produced by wire arc additive manufacturing through test programs. The stainless steel plates were first additively manufactured using cold metal transfer technology with three types of feedstock wires (ER304, ER308L, ER316L). Tensile coupon specimens and microstructural observation samples were extracted from the WAAM plates. The electron backscatter diffraction (EBSD) experiments were conducted to identify and analyze the microstructures of the WAAM austenitic stainless steels. Five test orientations, namely θ = 0˚, 30˚, 45˚, 60˚, 90˚ relative to the printing layer direction, were designed to investigate the mechanical properties anisotropy. Two types of specimen surface condition (milled type and as-built type) were considered to assess the impact of geometric undulation. The geometric features of the as-built specimens were obtained using 3D laser scanning. A total of 60 tensile tests with the aid of digital image correlation (DIC) system were conducted to obtain the stress–strain responses of the WAAM austenitic stainless steels. The mechanical properties anisotropy of the WAAM austenitic stainless steels was analyzed in detail.

Effect of hot rolling on microstructure and mechanical properties of hot isostatically pressed 30CrMnSiNi2A ultrahigh strength steel

The prior particle boundaries (PPBs) are a typical powder metallurgy (PM) defect, which usually leads to the deterioration of mechanical properties in PM materials. In this study, two different hot rolling modes (unidirectional rolling and cross rolling) are designed to improve PPBs in hot isostatic pressed (HIPed) 30CrMnSiNi2A ultrahigh strength steel. The microstructure, mechanical properties and fracture features of the HIPed compact, the hot unidirectional rolled (HURed) and hot cross rolled (HCRed) sheets are systematically compared. The results manifests that hot rolling has a significant influence on size and distribution of PPBs. PPBs in HIPed compact are comprised of Al-rich oxides which is distributed along particle boundaries. After hot rolling, large PPBs inclusions are crushed and the size of PPBs are mostly concentrated in 0–0.20 μm. Unidirectional rolling makes continuous PPBs structure broken into short-chain fragments and dispersed oxides completely, while cross rolling makes most of continuous PPBs structure maintained and only a few oxides are dispersed. Excellent mechanical properties are obtained by hot rolling, reflecting on an ultimate tensile strength (UTS) of about 2.0 GPa, a total elongation (TE) of 17.9 %, a Charpy impact energy of 28.6J along rolling direction and a UTS of over 2.1 GPa, a TE of 16.1 %, a Charpy impact energy of 18.1J along transverse direction, respectively. High performances can be attributed to formation of martensite, grain refinement, improvement of PPBs and work hardening. Furthermore, hot-rolled samples manifests an obvious anisotropy in mechanical properties. The HCRed sample reveals a lower anisotropy compared to the HURed sample, mainly owing to differences of PPBs distribution and rolling textures.

Implementation and evaluation of curved layer fused deposition modeling

Fused Deposition Modeling (FDM) is an extrusion-based additive manufacturing (AM) process in which a thermoplastic material is extruded through a nozzle. Although it was initially developed for rapid prototyping, advances in the FDM technology have rapidly increased its range of applications. However, the FDM process has inherent disadvantages, such as poor surface finish, severe anisotropic mechanical properties, and increased build time for high-resolution parts. This is the result of the layer-by-layer manufacturing process. To remedy these issues, Curved Layer Fused Deposition Modeling (CLFDM) offers a new building paradigm for FDM in which the material is deposited in curved nonplanar layers. The purpose of this study is to implement a curved-layer toolpath generation algorithm and quantify the benefits of the curved layered methodology over traditional planar layers in printing thin-contoured parts.

Forging Treatment Realized the Isotropic Microstructure and Properties of Selective Laser Melting GH3536

The anisotropy of mechanical properties in SLMed alloy is very important. In order to realize the homogeneity of the microstructure and mechanical properties of GH3536 alloy prepared by selective laser melting (SLM), the as-deposited samples were treated by hot isostatic pressing and then forged at different temperatures. The microstructure, grain size, room- and high- temperature tensile properties, and endurance properties of the samples were studied. The results showed that the microstructure of the sample was mainly equiaxed austenite phase, and granular carbides were precipitated inside the grains after forging treatment, resulting in the anisotropy of the sample almost disappearing. The grain boundary phase difference distribution was most concentrated at 60°. The grain size was less than 10 μm, and a large number of twins were formed. With the increase in forging temperature, the yield strength, tensile strength, and contraction of area of the samples changed little, and the properties parallel to the z-axis (parallel samples) and vertical to the z-axis (vertical samples) were almost the same. In particular, the yield strength, tensile strength, and contraction of area in the transverse and vertical samples were almost at the same level. Judging from the elongation after fracture and the contraction of area, the properties of the samples showed characteristics of anisotropy after a high temperature endurance test.

Effect of grain boundary Widmanstätten α colony on the anisotropic tensile properties of directed energy deposited Ti-6Al-4V alloy

Columnar grain structure caused anisotropy in mechanical properties, especially in elongation, is an important concern for Ti-6Al-4 V alloy fabricated by directed energy deposition (DED). Several strategies have been proposed to reduce anisotropy by globularizing the grains, but these conventional approaches are costly and inefficient due to challenges faced during producing the columnar β-grain structures. However, understanding the impact of columnar grain-related microstructures on the anisotropic deformation behavior is still necessary. Despite the recognition of the importance of grain boundary Widmannstätten α colony (αWGB) as a grain-related microstructure, it has received limited attention in available literature on anisotropy in mechanical properties. This study employed in-situ induction heating during DED to control αWGB formation, yielding three Ti-6Al-4 V samples with varying αWGB sizes. Anisotropic deformation of αWGB and its impact on elongation in build and transverse directions were analyzed. αWGB width grew from 0.5 µm to 32.4 µm via diffusion-controlled growth due to reduced cooling rate. Transverse deformation led to dislocation movement and accumulation, causing early failure and worsened ductile anisotropy within αWGB. Notably, larger αWGB size significantly exacerbated anisotropy in ductility. This work underscores αWGB's role in anisotropic deformation and offers insights for optimizing mechanical properties in DED-fabricated titanium alloys.

Mechanical properties and microstructure characteristics of wire arc additively manufactured high-strength steels

Additive manufacturing is a revolutionary emerging technology in the manufacturing industry. Wire arc additive manufacturing (WAAM) is a metal additive manufacturing technology suitable for the production of medium to large steel elements of structure. The aim of this study is to investigate the microstructural and mechanical behavior of high-strength steels produced by WAAM through experimental program. The test specimens were additively manufactured from three types of feedstock wires (ER100S-G, ER110S-G, ER120S-G). The microstructure characteristics of WAAM high-strength steels were identified. The tensile coupon specimens were extracted from flat regions of the WAAM runway-shaped steel tubes at five orientations θ = 0˚, 30˚, 45˚, 60˚, 90˚ with respect to the print direction to investigate the anisotropy of mechanical properties. Both the milled and as-built specimens were included to study the impact of geometric irregularity. The dimensions of the as-built specimens were measured using 3D laser scanning and the geometric characteristics were discussed. A total of 60 tensile tests were conducted with the assistance of digital image correlation (DIC) system in order to investigate the stress–strain responses of WAAM high-strength steels. Details of test program, including the specimen design, test setup and key test results, are presented. The anisotropy of WAAM high-strength steel specimens in terms of both the geometries and mechanical properties are discussed.

Single track versus bulk samples: Understanding the grain refinement in inoculated ferritic stainless steels manufactured by powder bed fusion-laser beam

One generic challenge in powder bed fusion - laser beam (PBF-LB) is the formation of epitaxially grown columnar grains, which lead to the undesirable anisotropy of mechanical properties. This anisotropy could be rectified by ex-situ or in-situ inoculation in some particular alloy systems. Understanding the grain refinement mechanism caused by in-situ inoculation is, however, complicated by remelting caused by the overlapping between neighboring scan tracks, when printing bulk samples using multiple tracks. Here in this work, a series of single tracks using ferritic stainless steels feedstock powder with and without pre-alloyed inoculant-forming elements, were printed at different scanning speeds to gain refreshed understanding on the mechanism of the observed grain refinement. Interestingly, the grain refinement in single tracks and bulk samples printed from the powder with and without inoculant-forming elements showed an opposite tendency. When using the powder without inoculant-forming elements, the single tracks showed large columnar grains, while the bulk samples showed even larger grain sizes; when using the powder with pre-alloyed inoculant-forming elements, fine equiaxed grains are found at the centers of the melt pools, surrounded by slightly coarser columnar grains at melt pool boundaries, in both single tracks and bulk samples. Noticeably, the mean grain sizes in the bulk samples are however smaller compared to those for single tracks because of remelting. Our work provides new insights on the grain refinement via in-situ inoculation during the PBF-LB process and highlights the importance of studying single tracks to better understand the melting and solidification behavior.

Influence of vacancies on the stability and mechanical properties of V2AlC: Guidelines for etching MAX phases via ab initio calculations

This study focuses on the ideal etching of defective MAX phases in a mechanical exfoliation process to produce vanadium-based MXenes. Two-dimensional MXenes exhibit high structural stability and excellent electrical conductivity, and can be applied as electrode materials. Mechanical exfoliation can be facilitated by modifying the vacancy in the V2AlC MAX phase, which makes etching challenging. We report the effects of M (vanadium), A (aluminum), and X (carbon) vacancies on the mechanical behavior of V2AlC via ab initio calculations. To this end, the anisotropic mechanical properties and strain–stress curves were calculated for MAX phases with different vacancies (x = 0.08, which corresponds to 8.33 at.%). The presence of vanadium vacancies significantly deteriorated the structural and mechanical properties compared to those of aluminum and carbon vacancies. Thus, it was confirmed that vanadium vacancies had a significant effect on the mechanical exfoliation of the MAX phases. These findings provide further insights into the design of MXenes.

A comparative ab initio study on mechanical and thermal properties of rare-earth scandate LnScO3 (Ln = La, Pr, Nd, Sm, Eu and Tb) compounds

To comparatively examine the mechanical and thermal properties of rare-earth scandate LnScO3 (Ln = La, Pr, Nd, Sm, Eu and Tb) compounds, ab initio calculation based on density functional theory was used within the framework of the generalized gradient approximation. The elastic moduli, Pugh’s criterion, Poisson’s ratio, Vickers hardness, linear compressibility, Debye temperature, Grüneisen parameter, elastic wave velocities, minimum thermal conductivities of LnScO3 were successfully obtained from independent single crystal elastic coefficients. The computed elastic constants indicate that these compounds have mechanical stability. The ductile and brittle properties of LnScO3 compounds were investigated using the B H /G H , Poisson’s ratio and Cauchy pressure. The mechanical anisotropic properties of LnScO3 compounds were discussed using universal anisotropic index, shear anisotropy factors, percentage shear (compressible) anisotropy index. Minimum thermal conductivities of LnScO3 were determined using Cahill’s and Clark’s model. Except for the elastic coefficients of NdScO3, SmScO3 and TbScO3 compounds, many physical properties of LnScO3 compounds were calculated for the first time in this study. We compared our calculation results with experimental and other theoretical data available in the literature.

Strong, tough, anisotropic, flexible, and transparent bamboo films

Bamboo has higher strength, better toughness, and a shorter growth cycle than wood. It is of great significance to use top-down nanotechnology to construct high-performance bamboo film (BF) instead of petroleum-based plastic film. However, bamboo lacks lateral cell tissues, and its structure is prone to disintegration when the components are removed. Herein, slice bamboo veneers (SBV) were used as building blocks, and a sequential process of alkali pretreatment-crosslinking-delignification-compression densification was conducted to fabricate the high-performance BF. The oriented arrangement of nanofibers, highly dense microstructure, and a large number of hydrogen bonds between cellulose microfibrils endowed BF with anisotropic and excellent mechanical and optical properties. The longitudinal tensile strength and toughness of the prepared BF were 656.6 MPa and 33.7 MJ m−3, respectively, and its light transmittance and haze were 70.2% and 88.1%, respectively. In addition, BF has good thermal insulation with a thermal conductivity of 0.0857 W m−1 K−1. The combined characteristics of BF, including high strength, high toughness, flexibility, anisotropy, high optical transmittance, and thermal insulation, make them suitable to be applied as optoelectronic substrates, insulating building materials, and green packaging materials.

High-Temperature Tensile Mechanical Properties and Microstructure of Rolled 6082-T6 Aluminum Alloy Sheets.

The tensile properties of rolled 6082-T6 aluminum alloy were tested at a high temperature, and the influences of tensile temperature on its flow stress and anisotropy were studied. The microstructure evolution was characterized using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). It was concluded that the tensile strength of the studied alloy decreases with increasing temperature. In higher-temperature deformation, the dislocation density decreases alongside the coarsening of precipitates, leading to a decrease in deformation resistance, and increase in the number of dimples and deepening of their sizes, exhibiting good plasticity. The alloy displays anisotropic mechanical properties at 200 °C due to the elongated grains and the orientation of the α-phase. The anisotropy becomes weaker with increasing temperature. There is no evident anisotropy at 400 °C, as the slip systems are activated more easily and the grains begin to recrystallize.