Anisotropic Tensile Properties Research Articles

Anisotropic tensile and degradation properties of as-extruded Mg-6Zn-2Sn-0.5Mn alloy

The anisotropic tensile and biodegradation properties of as-extruded Mg-6Zn-2Sn-0.5Mn alloy were studied in the present work. The results showed that the alloy exhibited refined grains and second phases, and {0001} basal planes aligned approximately parallel to the extrusion direction (ED). The tensile properties were tested parallel and perpendicular to ED, respectively, the results indicated that the tensile and yield strength of the extruded alloy were anisotropic, and ED sample had the higher strength. The corrosion resistance of the extruded alloy exhibited anisotropy as well, the corrosion rates evaluated by electrochemical tests and immersion measurements suggested that ED sample experienced slighter corrosion. The anisotropic tensile and degradation properties of extruded Mg-6Zn-2Sn-0.5Mn alloy were attributed to the basal planes and grain refinement.

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.

Effect of thermomechanical processing on compressive mechanical properties of Ti–15Mo additively manufactured by laser metal deposition

A bidirectional powder deposition strategy was employed to additively manufacture Ti–15Mo wt% using laser metal deposition. The as-built alloy was subsequently subjected to post-fabrication uniaxial thermomechanical processing at strain rates of 0.00055s−1, 0.0011s−1, 1s−1, and 4s−1, with strains of 20 % and 40 %. Experiments were conducted at room and elevated temperatures. Phase identification, elemental and microstructural characterisation were conducted using x-ray diffraction, energy dispersive spectroscopy and scanning electron microscopy. The three distinct zones, namely the fusion, remelted and heat affected zones, identified in each deposited layer of the as-built microstructure were retained after thermomechanical processing. After processing, electron backscatter diffraction was used to analyse deformation mechanisms. Deformation accommodation in β matrix was predominantly by a combination of slip and α′′ martensite which formed as a primary product at columnar and sub-columnar grain boundaries. However, the operation of {332}⟨113⟩ and {112}⟨111⟩ β-twinning was also determined, howbeit with a very small surface fraction. This implies a small surface fraction of secondary α′′ martensite forming within β-twins in the deformed microstructure. Compressive mechanical properties showed a strong dependence on strain rate as higher flow stress and compressive strength were obtained at higher strain rates. Grain structure homogenisation was not achieved after thermomechanical processing as there were α dominated regions as well as martensite/twin dominated regions which implies that an-isotropic tensile properties would emerge after tensile deformation on multiple pre-TMCPed samples. However, columnar β-grains were refined by a combination of precipitated α and deformation induced β-twins and martensite.

Estimation of Planar and Normal Anisotropy Parameters of Al 8011 Sheets as Cold Rolled and Cold Rolled with Annealed Condition

Aluminium 8011 cast plates subjected to cold rolling to reduce thickness from 12 mm to 3.5 sheets. As rolled aluminium sheet was subjected to annealing treatment after rolling. This work deals with the study of planar and normal anisotropy parameters of as rolled aluminium and rolled with annealed aluminium sheets. The tensile test samples were cut at 0°, 30°, 45°, 60° and 90° with respect to the rolling direction of as rolled Al sheet and rolled with annealed Al sheet. Tensile properties were measured at different orientations to the rolling directions. The wide variation in tensile strength was found in case of as rolled Al samples at different orientation to rolling direction of sheet (208 to 243 MPa). On the other hand nearly uniform tensile strength (128 MPa to 132 MPa) was measured for rolled and annealed Al samples at different orientations. As rolled Al samples shows anisotropic tensile properties where as isotropic tensile properties were measured for rolled with annealed Al samples. Al grains are more elongated along the rolling directions where as rolled and annealed Al sample shows more equiaxed grains which is attributed to isotropic behaviour of Al sheets. The normal anisotropy parameter or average rm value is higher (1.24) in case of rolled and annealed sheet sample as compared to as rolled Al sheet rm value (1.06). This is attributed to isotropic behaviour of rolled and annealed samples. Toughness and ductility properties are improved more than 3 times in case of rolled and annealed Al sheet samples. Annealing treatment of rolled Al sheet samples shows elongated grain morphology changes to equiaxed grains of aluminum which tends to improved formability and isotropic mechanical properties Al sheet. For determination of normal anisotropy (rm) value, tensile results R values are required at angles of 0 degrees, 45 degrees, and 90 degrees. However in this study additional R values are estimated at 30 degree and 60 degree in order to understand trend of R value at every 30 degree from 0 to 90 degree.

The synergic effects of heat treatment and building direction on the microstructure and anisotropic mechanical properties of laser powder bed fusion Corrax maraging stainless steel

An anisotropic microstructure and mechanical properties are big challenges in the development of various laser powder bed fusion (LPBF) alloys. This study investigated the roles of heat treatment and building direction (BD) on the microstructure and anisotropic mechanical properties of LPBF Corrax maraging stainless steel. The effects of solution treatment (ST) and integrated solution-aging treatment (SAT) were clarified. The results show that the grain size of martensite, amount of austenite, and features of grain boundaries were slightly varied with the building direction due to the thermal history. In the as-built state, the weak <111>α′||BD, <1 1‾ 0>α′||X, and <001>α′||BD textures could be found. After the SAT process, the <1 1‾ 0>α′||X texture was slightly intensified due to the coarsening of large columnar grains. However, the texture of the SAT sample was still weak.Furthermore, the building direction and heat treatment did not lead to obvious anisotropic tensile properties or change the ductile fracture mode. The weak texture and pores in LPBF Corrax did not dominate the tensile properties. Irrespective of sample state, the horizontally-built samples exhibited comparable strengths and slightly higher elongation than the vertically-built ones did. In the as-built condition, this phenomenon can be mainly attributed to the transformation-induced plasticity effect. In the ST and SAT conditions, smaller grain sizes of martensite and higher high-angle grain boundary ratios in the horizontally-built samples provided more resistance to crack propagation. LPBF Corrax maraging stainless steel exhibited superior tensile performances and low anisotropic tensile properties, which are very beneficial to the stability of the material during service.

Effects of Loading Direction on the Anisotropic Tensile Properties of Duplex Stainless Steels Based on Phase Strains Obtained by In Situ Neutron Diffraction Experiments

Effects of Loading Direction on the Anisotropic Tensile Properties of Duplex Stainless Steels Based on Phase Strains Obtained by In Situ Neutron Diffraction Experiments

Broadband Acoustoelectric Conversion Based on Oriented Polyacrylonitrile Nanofibers and Slit Electrodes for Generating Power from Airborne Noise

Electrospun nanofiber acoustoelectric devices typically have a bandwidth in the range of 100-400 Hz, which limits their applications. This study demonstrates a novel device structure with tunable acoustoelectric bandwidth based on oriented electrospun polyacrylonitrile (PAN) nanofibers and slit electrodes. When the PAN nanofibers were arranged perpendicular to the slits, the devices had a much wider bandwidth than their parallel counterparts, while the latter had a bandwidth similar to that of randomly oriented nanofibers. In all devices, the electrical outputs follow a similar trend with the slit aspect ratio. However, the slit number only affected the electrical output without changing the bandwidth characteristic. We further showed that both the slit electrode and the oriented nanofiber membranes played a role in tuning the frequency response. Under sound, the vibration of the electrode caused the slit to be misaligned on both sides. The anisotropic tensile properties of the oriented nanofiber membranes allowed the fibers to stretch differently depending on their angle of alignment with the slits. Those perpendicular to the slits received more intense stretching, contributing to a wider bandwidth. The wider bandwidth increases the electrical output, especially when harvesting multifrequency sound. A 4 × 3 cm2 device made of five-slit electrodes (slit width × length, 2 mm × 30 mm) with PAN nanofibers perpendicular to the slits showed a bandwidth of 100-900 Hz and electrical outputs of 39.85 ± 1.34 V (current output 6.25 ± 0.18 μA) under 115 dB sound conditions, which is sufficient to power electromagnetic wireless transmitters. When one such slit device was used as a power supply and another as a sound sensor, they formed a completely self-powered wireless system that could detect sounds from various scenarios, such as high-speed trains, airports, highway traffic, and manufacturing industries. The energy can also be stored in lithium-ion batteries and capacitors. We hope that such novel devices will contribute to the development of highly efficient acoustoelectric technology for generating electrical energy from airborne noise.

Effects of post-heat treatment on anisotropic mechanical properties of laser additively manufactured IN718

In this presented work, the effects of different heat treatments on the anisotropic mechanical properties of Inconel 718 (IN718) fabricated by laser powder bed fusion (LPBF) and laser directed energy deposition (LDED) were comparatively investigated. Samples prepared in build direction (BD) and transverse direction (TD) for tensile and creep tests were heat-treated with Solution + double aging (SA) and Homogenization + solution + double aging (HSA) procedures, separately. Experimental results indicate that both SA-treated LPBF-IN718 and LDED-IN718 show strong anisotropy in tensile and creep properties. TD samples have higher tensile strength and relatively better creep performance. After HSA treatment, LPBF-IN718 samples still show strong anisotropic tensile and creep properties. In contrast, anisotropy in mechanical properties of LDED-IN718 samples is mitigated significantly. The columnar grains in as-built LDED-IN718 recrystallized after HSA treatment, resulting in similar tensile and creep properties in both directions. The difference in residual stresses of LPBF-IN718 and LDED-IN718 is the main reason that causes the totally different conditions after HSA treatment. This work can provide a deeper understanding of the difference in anisotropic mechanical properties of LPBF-IN718 and LDED-IN718, which may guide the design of proper heat treatment of laser additively manufactured nickel-based superalloy potentially.

Anisotropic microstructure, properties and molecular dynamics simulation of CoCrNi medium entropy alloy fabricated by laser directed energy deposition

CoCrNi medium entropy alloy additive part was fabricated by laser directed energy deposition process. Based on an optimized additive manufacturing process parameters, the microstructure, tensile properties and corrosion performance in the XOY and XOZ planes were compared to learn the anisotropic properties of the additive part. The majority of the additive parts consisted of equiaxed grains, a small proportion consisted of elongated needle-like grains. The equiaxed and elongated needle-like grains in the XOY plane were finer compared to that in the XOZ plane. The corrosion electrochemical activity is uniform in the XOY plane, but varies at different heights in the XOZ plane base on scanning vibrating electrode technique results. Electron backscatter diffraction results near the fracture indicated a larger and relatively more homogeneous residual stress peak in the XOY plane. The tensile and yield strengths in the XOZ plane were lower than those in the XOY plane by approximately 98.5 MPa and 19.1 MPa. While the elongation in the XOZ plane was more than twice as high as that in the XOY plane. The reason for the anisotropic tensile behavior was the strong texture in the XOY plane and the relatively random grain orientation in the XOZ plane. Single crystal and polycrystalline molecular dynamics were used to simulate the anisotropic tensile properties in the XOZ and XOY planes. Single crystal simulation results showed that the maximum stress was 19.0 GPa and elongation was 13.0% when the stretching was along the [110] crystal orientation. The minimum stress was 17.1 GPa and elongation is 11.1% elongation when the stretching was along the [11 1‾] crystal orientation. Anisotropy existed for CrCoNi alloys in terms of tensile properties along different orientations. Polycrystalline simulation in the XOY plane results showed that the main cause of anisotropy between them was the tangling of the 1/6<112> dislocations and the 1/6<521> dislocations, which caused obstacles to dislocation motion and thus improved the strength of CoCrNi additive parts. High tensile strength in the XOY plane, not the XOZ plane, was attributed to 1/6<112> and 1/6<521> dislocation tangles at the (1 1‾ 0)/(115) planes.

Bioprinting of structurally organized meniscal tissue within anisotropic melt electrowritten scaffolds.

The meniscus is characterised by an anisotropic collagen fibre network which is integral to its biomechanical functionality. The engineering of structurally organized meniscal grafts that mimic the anisotropy of the native tissue remains a significant challenge. In this study, inkjet bioprinting was used to deposit a cell-laden bioink into additively manufactured scaffolds of differing architectures to engineer fibrocartilage grafts with user defined collagen architectures. Polymeric scaffolds consisting of guiding fibre networks with varying aspect ratios (1:1; 1:4; 1:16) were produced using either fused deposition modelling (FDM) or melt electrowriting (MEW), resulting in scaffolds with different internal architectures and fibre diameters. Scaffold architecture was found to influence the spatial organization of the collagen network laid down by the jetted cells, with higher aspect ratios (1:4 and 1:16) supporting the formation of structurally anisotropic tissues. The MEW scaffolds supported the development of a fibrocartilaginous tissue with compressive mechanical properties similar to that of native meniscus, while the anisotropic tensile properties of these constructs could be tuned by altering the fibre network aspect ratio. This MEW framework was then used to generate scaffolds with spatially distinct fibre patterns, which in turn supported the development of heterogenous tissues consisting of isotropic and anisotropic collagen networks. Such bioprinted tissues could potentially form the basis of new treatment options for damaged and diseased meniscal tissue. STATEMENT OF SIGNIFICANCE: This study describes a multiple tool biofabrication strategy which enables the engineering of spatially organized fibrocartilage tissues. The architecture of MEW scaffolds can be tailored to not only modulate the directionality of the collagen fibres laid down by cells, but also to tune the anisotropic tensile mechanical properties of the resulting constructs, thereby enabling the engineering of biomimetic meniscal-like tissues. Furthermore, the inherent flexibility of MEW enables the development of zonally defined and potentially patient-specific implants.

Elastomeric Trilayer Substrates with Native-like Mechanical Properties for Heart Valve Leaflet Tissue Engineering.

Heart valve leaflets have a complex trilayered structure with layer-specific orientations, anisotropic tensile properties, and elastomeric characteristics that are difficult to mimic collectively. Previously, trilayer leaflet substrates intended for heart valve tissue engineering were developed with nonelastomeric biomaterials that cannot deliver native-like mechanical properties. In this study, by electrospinning polycaprolactone (PCL) polymer and poly(l-lactide-co-ε-caprolactone) (PLCL) copolymer, we created elastomeric trilayer PCL/PLCL leaflet substrates with native-like tensile, flexural, and anisotropic properties and compared them with trilayer PCL leaflet substrates (as control) to find their effectiveness in heart valve leaflet tissue engineering. These substrates were seeded with porcine valvular interstitial cells (PVICs) and cultured for 1 month in static conditions to produce cell-cultured constructs. The PCL/PLCL substrates had lower crystallinity and hydrophobicity but higher anisotropy and flexibility than PCL leaflet substrates. These attributes contributed to more significant cell proliferation, infiltration, extracellular matrix production, and superior gene expression in the PCL/PLCL cell-cultured constructs than in the PCL cell-cultured constructs. Further, the PCL/PLCL constructs showed better resistance to calcification than PCL constructs. Trilayer PCL/PLCL leaflet substrates with native-like mechanical and flexural properties could significantly improve heart valve tissue engineering.

Anisotropic Tensile Properties in Ni-Based Single-Crystal Superalloy DD6 near [001] Orientation at 760°C

This work is concerned the tensile properties of the secondary Ni-based single-crystal superalloy DD6 near [001] orientation at 760°C. In this study, anisotropic tensile properties of DD6 alloy within 10° of the [001] orientation were exhibited at 760°C. The yield strength and ultimate tensile strength of DD6 alloy oriented close to [001] direction was the highest. As the deviation off the [001] orientation increased, both 0.2% yield strength and ultimate tensile strength was decreased. The specimens oriented close to [001]-[111] boundary exhibit higher yield strength and ultimate tensile strength than the specimens oriented close to [001]-[011] boundary. Numerous of dislocations can be found in the γ matrix channels during the tensile deformation. A number of dislocation pairs and few of stacking faults are found in the γ' precipitates after the tensile at 760°C. The morphology of γ' phases in DD6 alloy maintained cubical during the tensile deformation at 760°C. With Schmid's Law, the mechanism of anisotropic tensile properties in DD6 alloy near [001] orientation is analyzed.

Homogenization of microstructure and mechanical properties of wire arc additive manufactured martensitic stainless steel through optimization of post-process heat treatment

A single-bead multilayer martensitic stainless steel thin wall was fabricated using the wire arc additive manufacturing (WAAM) process. After the WAAM process, the tempering heat treatment was carried out to homogenize the microstructure distribution in the wire arc additive manufactured (WAAMed) part. To optimize the tempering temperature, the as-WAAMed samples were subjected to varying tempering temperatures of 300, 500, 600, and 700 °C for 2 h. The heterogeneous structure within the as-WAAMed part was hardly eliminated by the low tempering temperatures of 300 and 500 °C. On the other hand, the inhomogeneous hardness profiles were significantly homogenized by the tempering temperature of 600 and 700 °C. Tempering at 600 °C removed the heterogeneous structure, resulting in the effective homogenization of the significantly heterogeneous hardness profile and microstructure distribution in the as-WAAMed part. Tempering at 700 °C led to the lower hardness than that at 600 °C.The anisotropic tensile properties of the as-WAAMed part were also eliminated after tempering at 600 °C. The significant differences in the toughness of the different layers of the as-WAAMed part were effectively reduced by proper tempering. The slight decrease in toughness of the post-process heat-treated sample from the bottom to the top of the thin wall was mainly caused by the increase in the martensitic block size inherited from the prior austenite grain structure. This study suggests that tempering at 600 °C for 2 h is an effective post-process heat treatment to homogenize the microstructure and mechanical properties of as-WAAMed 2Cr13 martensitic stainless steel.

Heterogeneous microstructure and anisotropic mechanical properties of reduced activation ferritic/martensitic steel fabricated by wire arc additive manufacturing

• Reduced activation ferritic/martensitic steel was fabricated by wire arc additive manufacturing. • The as-deposited microstructure exhibited the heterogeneous band characteristics. • Microstructure differences caused the periodical hardness and anisotropic tensile properties. • A potentially detrimental softening zone, was found at the heat-affected zone of the as-deposited RAFM steel. Reduced activation ferritic/martensitic (RAFM) steel is an iron-based alloy as a candidate structural material in fusion reactor. This paper evaluates the compatibility of RAFM steel as a choice material for wire arc additive manufacturing (WAAM). Two specimens of RAFM steels with high and low heat input were fabricated by WAAM. The effects of the heat input on the microstructure, microhardness and tensile properties of samples were investigated. The fusion boundaries are spaced uniformly in the whole sample. Three distinctive zones were present in the periodic region, including heat-affected zone (HAZ), columnar grains zone and fine-grained zone occurred alternatively. The HAZ was affected by the heat input. The fully γ-annealed top region consisted of epitaxial elongated grains without HAZ. The periodic pattern in microhardness along the building direction was found which was related to the periodic microstructure featured. The tensile properties presented anisotropic characteristics due to the heterogeneous microstructure. Further analysis indicated that the grain coarsening in the HAZ and C precipitates distributed at the grain boundaries caused substantial softened in the HAZ, resulted in the lower localized microhardness and tensile strength. Compared to the high heat input specimen, the low heat input specimen had smaller grain sizes, higher microhardness and tensile properties.

Laser-based powder bed fusion of pre-alloyed oxide dispersion strengthened steel containing yttrium

In this study, the pre-alloyed powder Fe-22Cr-5.1Al-0.5Ti-0.26Y (wt%) was prepared by nitrogen atomization and characterized with the aid of focused ion beam (FIB) and transmission electron microscopy (TEM). The oxide dispersion strengthened (ODS) bulk material was successfully fabricated using laser-based powder bed fusion (PBF-LB). Micro-scale Y-Al-O complex oxides and nanoscale Y 2 O 3 @TiN core-shell structures were found in the as-built material. The importance of the presence of residual oxygen in the atomization system and the building chamber for the formation of dual-scale secondary phases was revealed. In addition, the formation mechanism of the dual-scale secondary phases was elucidated by investigating the phase and composition of the as-built ODS steel. Columnar crystals with {001}< 100 > cubic alignments grew epitaxially from the bottom of the molten pool during the PBF-LB process, forming a weak cubic texture in the as-built material. This cubic texture led to anisotropic tensile properties of the as-built material, where the room-temperature ultimate tensile strength in the XY-45° direction was higher than that in the building direction (Z). Our work provides a feasible scheme to shorten the preparation process of ODS alloys, which is usually carried out using complicated means. • The Y-containing pre-alloyed powder was prepared by nitrogen atomization. • Primary precipitates in the powder were characterized by FIB and TEM. • Residual oxygen participated in the alloying reaction in the molten metal. • Formation mechanisms of oxides and cubic texture were revealed.

Solute-induced near-isotropic performance of laser powder bed fusion manufactured pure titanium

Materials produced by laser-based powder bed fusion process ( L -PBF) undergo rapid solidification and several cycles of remelting. The resulting unique microstructure imparts anisotropy to the material and leads to its non-uniform deformation under load that can cause limitations in some applications. In this study, we explored the ability of nitrogen (solute) to reduce the degree of anisotropy of L -PBF fabricated Ti materials. The correlation among microstructural changes, texture evolution, and deformation behavior was investigated. L -PBF fabricated Ti with low N content (0.01 wt%) exhibits mainly continuous epitaxial growth of α grains with a strong crystallographic texture, leading to anisotropic tensile properties. A high N content (0.31 wt%) significantly changes the structure and texture of L -PBF fabricated Ti through the introduction of refined martensite grains with random crystallographic orientations, which reduces the degree of anisotropy and enhances strength (1066 MPa) and ductility (25%). This study will facilitate the manufacture of Ti with superior near-isotropic tensile properties, which has not been realized through traditional manufacturing processes.

Three-dimensional forming characteristics and mechanical property of additive manufacturing aluminium–copper alloys

The three-dimensional forming characteristics and mechanical properties of the Al–Cu alloy components, fabricated by the cold metal transfer-based wire arc additive manufacturing process with different deposition parameters, were analysed. A three-dimensional scanner is employed to test the geometrical forming characteristics of deposition components under different parameters. The results indicate that inappropriate heat input reduces the dimensional accuracy of the components. Based on the analysis of the mechanical properties of deposited components, the tensile strength and the elongation increase with the increase in deposited heat input. Meanwhile, the anisotropic tensile properties in the components are more significant. Higher ultimate tensile strength is obtained in the deposition direction than perpendicular to the deposition direction.

Decellularization of porcine esophageal tissue at three diameters and the bioscaffold modification with EETs‐ECM gel

Damaged complex modular organs repair is a current clinical challenge in which one of the primary goals is to keep their biological response. An interesting case of study it is the porcine esophagus since it is a tubular muscular tissue selected as raw material for tissue engineering. The design of esophageal constructs can draw on properties of the processed homologous extracellular matrix (ECM). In this work, we report the decellularization of multilayered esophagus tissue from 1-, 21- and 45-days old piglets through the combination of reversible alkaline swelling and detergent perfusion. The bioscaffolds were characterized in terms of their residual composition and tensile mechanical properties. The biological response to esophageal submucosal derived bioscaffolds modified with ECM gel containing epoxyeicosatrienoic acids (EETs) was then evaluated. Results suggest that the composition (laminin, fibronectin, and sulphated glycosaminoglycans/sGAG) depends on the donor age: a better efficiency of the decellularization process combined with a higher retention of sGAG and fibronectin is observed in piglet esophageal scaffolds. The heterogeneity of this esophageal ECM is maintained, which implied the preservation of anisotropic tensile properties. Coating of bioscaffolds with ECM gel is suitable for carrying esophageal epithelial cells and EETs. Bioactivity of EETs-ECM gel modified esophageal submucosal bioscaffolds is observed to promote neovascularization and antiinflammatory after rabbit full-thickness esophageal defect replacement.

Effects of Zn Addition on the Microstructure and Mechanical Properties of As-Extruded Mg-2Al-0.5Ca Alloy

The effects of Zn addition on the microstructure and tensile properties of as-extruded Mg-2Al-0.5Ca-xZn (x = 0, 0.3, 0.6, 0.9 wt.%) alloys were investigated in this work. The results showed that the extruded sheets exhibited a completely dynamically recrystallized microstructure, the grain size was refined, and texture weakening was achieved with Zn addition because of the segregation of Zn atoms on grain boundaries, which suppresses the growth of dynamic recrystallized grains. The addition of 0.6 wt.% Zn improved both the tensile strength and ductility of the as-extruded Mg-2Al-0.5Ca alloy. The as-extruded Mg-2Al-0.5Ca-0.6Zn alloy showed a 0.2% proof stress of 145 MPa, an ultimate tensile strength of 317 MPa, and an elongation of 30.0% along the extruded direction. The simultaneous improvement of strength and ductility was mainly due to the fine and homogeneous grain microstructure and the weakened extrude direction (ED)-tilted texture. The as-extruded Mg-2Al-0.5Ca-0.6Zn alloy showed little in-plane anisotropic tensile properties, with a 0.2% proof stress, ultimate tensile strength, and elongation in the 45° direction of 148 MPa, 299 MPa, and 25.0%, and those in the transverse direction of 148 MPa, 269 MPa, and 16.8%, respectively.

Effect of heat treatment temperature on microstructure and tensile properties of austenitic stainless 316L using wire and arc additive manufacturing

The effect of heat treatment temperature on the microstructure and tensile properties of 316L stainless steel fabricated by wire and arc additive manufacturing was studied in this paper. Heat treatment was used to uniformize the microstructure, eliminate the anisotropic tensile properties in as-built 316L part, and improve the poor elongation caused by the multilayered structure of alternating re-melting area (RA) and overlapping area (OA). The results showed that the heat treatments below 1000 °C had no significant effect on the multilayered structure and columnar austenite grains, but only changed the morphology and content of ferrite and σ phase within the grains. With the increase of the heat treatment temperature, ferrite transformed into σ phase and the fraction of second phase gradually decreased, leading to the slight increase of elongation but decrease of material strength and its anisotropic degree. After solution annealing above 1000 °C, the ferrite and σ phase was nearly dissolved in the austenite matrix. The austenite recrystallized and the multilayered structure was destroyed, which played a major role in the tensile properties. With the increase of heat treatment temperature, the fraction of recrystallization increased, resulting in decrease of material strength. The elongation was greatly improved and reached that of the annealed state, and its anisotropic was almost eliminated.