Lower Ultimate Tensile Strength Research Articles

Effect of cryogenic coupled magnetic field treatment on the microstructure and mechanical properties on Ti-6Al-4V titanium alloy

In this work, the effect of cryogenic coupled magnetic field (CCMF) treatment on the microstructure and mechanical properties of Ti-6Al-4V titanium alloy is investigated. The titanium alloy was subjected to different magnetic induced intensities (B) and under different treatment temperatures. The results show that the volume fraction of the β phase decreases with both a reduction in treatment temperature and an increase in B value. The CCMF-treated samples exhibit a higher dislocation density compared to those treated with cryogenic fields alone. When compared to samples that underwent either single cryogenic treatment or single magnetic treatment, the CCMF-treated samples demonstrate a lower ultimate tensile strength but a higher elongation. The integration of cryogenic and magnetic fields can significantly enhance the plasticity of the samples. In general, CCMF treatment can effectively enhance the plasticity of the samples while maintaining the material's strength, representing a promising new treatment method for titanium alloys.

Process Parameter Optimization of Directed Energy Deposited QT17‐4+ Steel

AbstractThe feasibility of using argon‐atomized QT 17‐4+ stainless steel powder for directed energy deposition (DED) additive manufacturing is studied. The QT 17‐4+ steel is a novel martensitic steel designed based on the compositional modification of the standard 17‐4 precipitation‐hardened (PH) stainless steel. This modification aims to achieve better mechanical properties of as‐deposited components compared to the heat‐treated wrought 17‐4PH steel. In this study, QT 17‐4+ steel powder is used for DED, for the first time. The influence of laser power, laser scan speed, powder feed rate, and hatch overlap on the density is studied. The central composite design is used to determine the experimental matrix of these factors. The response surface methodology is used to obtain the empirical statistical prediction model. Both columnar and equiaxed parent austenite grain structures are observed. X‐ray diffraction analyses reveal a decrease in the percentage of retained austenite from 19% in the powder to 5% after DED. The microhardness of the DED processed sample in the as‐deposited state is slightly higher than that of wrought 17‐4PH steel either solution‐annealed or H900‐aged. A higher 0.2% yield strength, a lower ultimate tensile strength, and lower elongation are observed for the vertically printed test sample, when compared to the horizontal one.

Multi-build orientation effects on microstructural evolution and mechanical behavior of truly as-built selective laser melting Ti6Al4V alloys

The unique combination of lightweight, strength, corrosion resistance, high-temperature resistance, and biocompatibility make Ti6Al4V alloy an important material in metal contact of solar cells, and selective laser melting (SLM) enables the production of Ti6Al4V parts complex geometries that would be difficult or impossible to produce using traditional manufacturing methods. The build orientation of SLM process presents an essential effect on the quality of the produced parts, and thus, in this study it investigates the impact of multi-build orientation (0°, 30°, 45°, 60°, 90°) on the microstructural evolution and mechanical behavior of truly as-built Ti6Al4V alloys produced by SLM. The microstructure analysis revealed the presence of ordered subsurface pores, located at a distance of about 50 μm–150 μm from the sample surface. The microstructure consisted primarily of α′ martensite with a small amount of β phase. Massive transformation was observed in the 30° and 45° samples, with corresponding grain sizes of 5 μm and 10 μm, respectively. To be specific, the content of β phase and ultimate tensile strength (UTS) varied with the sample orientation, and the 45° build orientation exhibited the highest content of β phase with value of approximately 2.8%, but also the lowest UTS and elongation, which were 1161 MPa and 3.99%, respectively.

Cold-welded joint characteristics of gold nanowires via atomistic simulation

This study examines the effects of contact depth, contact orientation, contact angle, and nanowires temperature on the tensile strength of the gold nanowire generated via the cold welding process. There is an increase in the deformation rate with increasing contact depth. From 5 Å to 20 Å, the lattice matching of the nanowires is good, leading to a good weld joint. The greatest ultimate tensile strength (UTS) value is achieved at 5 Å contact depth compared to other depth cases. The UTS value is sensitive to the change in the contact orientation and the contact angle. Compared to other orientations, the (001) vs (001) orientation has the highest rate of orientation matching with the highest FCC structure ratio. Other orientations obtain a much lower UTS value. When the contact angle rises, the UTS value mainly decreases due to the higher level of lattice mismatch. Compared to the other angle cases, the maximum UTS value is attained at 0º contact angle. Moreover, changing in nanowires temperature within the 250 K450 K range do not result in significant variations in the sample's surface morphology, structural transformation, or atomic strain. At 250 K, the sample has the highest UTS value compared to other temperature cases.

Microstructural evolution and mechanical properties of Ti55531–0.5Nb fabricated by selective laser melting under different heat treatments

The metastable Ti55531–0.5Nb alloy was deposited by selective laser melting (SLM) technology. The microstructure and phase orientation along different deposition directions were analyzed, and the microstructural evolution and mechanical properties of the alloy with different heat treatments have been investigated. It is indicated that the microstructures of the as-build samples were β phase without α phase, and the β phase orientation was dominated by 〈100〉 texture. The volume fraction of primary α decreases with increasing of solution temperature, while the secondary α exhibits an opposite trend, which is mainly related to the growth rate and dissolution rate α phase. The relatively higher ultimate tensile strength of 1300 ± 20 MPa and lower elongation of 2.4 ± 0.1% was observed when solution temperature is 790 °C, and the lower ultimate tensile strength of 1190 ± 8 MPa with higher elongation of 8.40 ± 0.6% was obtained at solution temperature of 700 °C. The tensile fracture exhibits a mixture fracture mode dominated by ductile fracture when there is primary α phase in the microstructure, while the brittle fracture was obtained owing to the absence of primary α phase. The crack nucleation mode is mainly microvoid coalescence, which mainly nucleate grain boundaries α phase and propagates along the grain boundary observed from the tensile fracture and cross-sectional microstructure near the fracture of tensile specimens. There results can provide some theoretical support for metastable β titanium alloys fabricated by additive manufacturing technology and subsequent heat treatment in the future.

Effect of Interlayer Composition on the Properties of Laser-Directed-Energy-Deposition-Based Additively Manufactured Copper-Stainless Steel Wall Structures

Laser-directed energy deposition (LDED) is one of the advanced techniques used for the sustainable manufacturing of engineering components with minimal material wastage and higher performance. This paper reports an investigation on LDED-based additive manufacturing of compositionally graded Copper (Cu)-stainless steel (SS) wall structures for improved performance of tooling components. Three different approaches, such as Cu-SS direct joint, 20% graded Cu-SS, and 50% graded Cu-SS, are used to build the wall structures. Optical microscopy of LDED-built graded samples reveals defect-free deposition of Cu-SS direct joint and 50% graded Cu-SS wall structures at identified process parameters, whereas the 20%-graded wall yields micro-cracks in the lower Cu region. The elemental distribution shows gradual traditions in the weight percentages of Cu and Fe along the built wall. Furthermore, the ultimate tensile strengths of the direct Cu-SS joint wall structure and the 50%-graded Cu-SS wall structure are higher than the strength of LDED-deposited Cu, while the 20%-graded Cu-SS wall structure has lower ultimate tensile strength than the strength of LDED-deposited Cu. Lower ultimate strength and failure in the lower-Cu zone of 20% graded Cu-SS wall structure can be attributed to the presence of micro-cracks in the Cu20SS80 zone of 20%-graded Cu-SS wall structures. The study establishes LDED as a technique for building multi-material components promoting sustainability in terms of manufacturing and component performance.

A Glutaraldehyde-Free Crosslinking Method for the Treatment of Collagen-Based Biomaterials for Clinical Application.

Biological bioprostheses such as grafts, patches, and heart valves are often derived from biological tissue like the pericardium. These bioprostheses can be of xenogenic, allogeneic, or autologous origin. Irrespective of their origin, all types are pre-treated via crosslinking to render the tissue non-antigenic and mechanically strong or to minimize degradation. The most widely used crosslinking agent is glutaraldehyde. However, glutaraldehyde-treated tissue is prone to calcification, inflammatory degradation, and mechanical injury, and it is incapable of matrix regeneration, leading to structural degeneration over time. In this work, we are investigating an alternative crosslinking method for an intraoperative application. The treated tissue's crosslinking degree was evaluated by differential scanning calorimetry. To confirm the findings, a collagenase assay was conducted. Uniaxial tensile testing was used to assess the tissue's mechanical properties. To support the findings, the treated tissue was visualized using two-photon microscopy. Additionally, fourier transform infrared spectroscopy was performed to study the overall protein secondary structure. Finally, a crosslinking procedure was identified for intraoperative processing. The samples showed a significant increase in thermal and enzymatic stability after treatment compared to the control, with a difference of up to 22.2 °C and 100%, respectively. Also, the tissue showed similar biomechanics to glutaraldehyde-treated tissue, showing greater extensibility, a higher failure strain, and a lower ultimate tensile strength than the control. The significant difference in the structure band ratio after treatment is proof of the introduction of additional crosslinks compared to the untreated control with regard to differences in the amide-I region. The microscopic images support these findings, showing an alteration of the fiber orientation after treatment. For collagen-based biomaterials, such as pericardial tissue, the novel phenolic crosslinking agent proved to be an equivalent alternative to glutaraldehyde regarding tissue characteristics. Although long-term studies must be performed to investigate superiority in terms of longevity and calcification, our novel crosslinking agent can be applied in concentrations of 1.5% or 2.0% for the treatment of biomaterials.

Influence of bimodal copper grain size distribution on electrical resistivity and tensile strength of silver - copper composite wires

In order to obtain the best compromise between high strength and low resistivity it was decided to introduce a controlled content of copper (Cu) large grains in copper-silver (Ag-Cu) composite wires. Composite powders are prepared by mixing of 1 vol% Ag nanowires and bimodal Cu powder. The so-obtained composites powders are consolidated into cylinders (8 mm in diameter and 30 mm long) by Spark Plasma Sintering (SPS) at only 450 °C. The cylinders served as starting materials for room temperature wire-drawing (WD) for the preparation of fine wires (1–0.2 mm diameter). The microstructure of the cylinders and the wires was investigated by scanning electron microscopy imaging and electron backscattered diffraction analysis. The electrical resistivity and the tensile strength were measured at 293 K and 77 K. The electrical resistivity of the wires is the lowest when the large Cu grain content is the highest. Cu large grains greatly limit the electronic scattering, forming areas with few grain boundaries and no Ag/Cu interfaces and therefore can be considered as fast conduction channels. Conversely, the addition of Cu large grains leads to a moderate decrease in mechanical strength. By presenting a 12 % lower electrical resistivity and an equivalent ultimate tensile strength (UTS) wires with bimodal Cu matrix show a better compromise between low electrical resistivity and high UTS (0.45 μΩ cm, 1082 MPa at 77 K) compared to wires with a fine-grained Cu matrix (0.51 μΩ cm, 1138 MPa at 77 K).

Mechanical properties of cross rolled CoCrFeMnNi high entropy alloy

In recent years, there has been a significant interest in high-entropy alloys (HEAs) due to their unique compositions, microstructures, and the ability to customize their properties. This study investigated the microstructure and deformation behaviour of the CoCrFeMnNi HEA under homogenised and rolled conditions. Two rolling methods were employed, namely two-step cross-rolling (TSCR) and multi-step cross-rolling (MSCR). Texture analysis revealed the development of Brass (Bs) {1 10} < 112 > and Goss (G) {011} < 100 > texture components in the samples, with an equivalent strain of 1.609. Notably, the MSCR technique involved rotating the samples at a 45° angle around the normal direction (ND) during alternate passes, which was a novel approach in this study. TSCR samples exhibited the formation of dense lamellar bands, while MSCR samples displayed dense dislocations forming a cell block-type structure. Vickers hardness testing revealed differing hardness outcomes as a result of varying deformation levels in samples. Specifically, the TSCR sample with 80% deformation exhibited the highest hardness, while the 50% deformed MSCR sample displayed a comparatively lower hardness. In the context of room-temperature tensile tests, the 80% deformed TSCR sample showed higher ultimate tensile strength but lower ductility. In contrast, the 80% deformed MSCR sample exhibited a slightly lower ultimate tensile strength but higher percentage elongation compared to the TSCR sample. These findings suggest that multi-step cross-rolling can effectively enhance the strength and ductility of HEAs, providing valuable insights for optimizing their mechanical properties. The microstructural and mechanical characterization presented in this study contributes to understanding deformation mechanisms and property optimization strategies in HEAs, thereby supporting their potential applications across various industries.

Low-Cycle Fatigue Behavior of Wire and Arc Additively Manufactured Ti-6Al-4V Material.

Additive manufacturing (AM) techniques, such as wire arc additive manufacturing (WAAM), offer unique advantages in producing large, complex structures with reduced lead time and material waste. However, their application in fatigue-critical applications requires a thorough understanding of the material properties and behavior. Due to the layered nature of the manufacturing process, WAAM structures have different microstructures and mechanical properties compared to their substrate counterparts. This study investigated the mechanical behavior and fatigue performance of Ti-6Al-4V fabricated using WAAM compared to the substrate material. Tensile and low-cycle fatigue (LCF) tests were conducted on both materials, and the microstructure was analyzed using optical microscopy and scanning electron microscopy (SEM). The results showed that the WAAM material has a coarser and more heterogeneous grain structure, an increased amount of defects, and lower ultimate tensile strength and smaller elongation at fracture. Furthermore, strain-controlled LCF tests revealed a lower fatigue strength of the WAAM material compared to the substrate, with crack initiation occurring at pores in the specimen rather than microstructural features. Experimental data were used to fit the Ramberg-Osgood model for cyclic deformation behavior and the Manson-Coffin-Basquin model for strain-life curves. The fitted models were subsequently used to compare the two material conditions with other AM processes. In general, the quasi-static properties of WAAM material were found to be lower than those of powder-based processes like selective laser melting or electron beam melting due to smaller cooling rates within the WAAM process. Finally, two simplified estimation models for the strain-life relationship were compared to the experimentally fitted Manson-Coffin-Basquin parameters. The results showed that the simple "universal material law" is applicable and can be used for a quick and simple estimation of the material behavior in cyclic loading conditions. Overall, this study highlights the importance of understanding the mechanical behavior and fatigue performance of WAAM structures compared to their substrate counterparts, as well as the need for further research to improve the understanding of the effects of WAAM process parameters on the mechanical properties and fatigue performance of the fabricated structures.

Experimental And Finite Element Analysis of Tensile Behavior of Stir Casted Magnesium Alloy Az91

In this present project work the significance of light weight material is discussed. The conventional light weight metal aluminum is replaced by magnesium. In addition magnesium based alloys are superior properties and most widely applicable in automobile and aircraft materials. High-quality samples of magnesium alloy AZ91 is fabricated through stir casting route. The use of wire cut EDM for sample preparation proved to be a reliable and accurate method for creating uniform samples with consistent dimensions. The ultimate tensile strength (UTS) of the magnesium alloy AZ91 obtained through the wire cut EDM tensile test was 174 MPa, indicating that the material is strong and able to withstand high levels of tensile stress. The ANSYS simulation predicted a slightly lower UTS value of 169 MPa, indicating that the simulation method may have made certain assumptions about the material's behavior that did not match the experimental results. The difference of 5 MPa between the experimental and simulated UTS values suggests that there may be some room for improvement in the simulation methods used in ANSYS software. The results of this study provide valuable information for engineers and materials scientists working with magnesium alloy AZ91, as they demonstrate the material's behavior under tensile loading and highlight potential areas for improvement. Hence the fabricated material is tested experimentally and numerically for its tensile properties. Hence the present work is significant for need of light weight material in automobile and aircraft applications.

Effect of friction stir welding parameters on microstructure and mechanical properties of the dissimilar alloys of AZ91D and AA7075

Friction stir welding is an efficient joining process for light metal alloys, offering benefits such as high joint efficiency and reduced grain sizes. This work is to investigate the process parameters that can improve the welding quality and reduce the brittle intermetallic compounds, including Al3Mg2 (β) and Al12Mg17 (γ) in the welded region. It was perceived that the process parameters influenced the morphological characteristics and input heat, thereby affecting the materialization of intermetallic compounds. The primary diffraction peaks of both Al and Mg were present in all the joints. Two specific intermetallic phases, Al3Mg2 and Al12Mg17, were formed as a result of the diffusion of Al and Mg atoms during welding. These intermetallic compounds were found in all the joints. The Al12Mg17 phase, when mixed with the Mg phase, tended to migrate towards the weld surface where the AZ91D plate was positioned. This migration might lead to constitutional liquation, which refers to the melting of specific phases during solidification, resulting in the materialization of eutectic microstructures. The highest ultimate tensile strength (UTS) value of 116.64 MPa was achieved with a rotational tool speed of 800 r/min and a traverse speed of 20 mm/min. On the other hand, the lowest UTS value of 68.32 MPa was observed with a rotational tool speed of 400 r/min and a traverse speed (TS) of 20 mm/min. It was noted that lower UTS values were associated with the materialization of dense layers of intermetallic compounds (Al12Mg17 and Mg + Al12Mg17) in the stir zone when using lower rotational tool speed and TS. It suggests that improper processing parameters can lead to the materialization of intermetallic compound in the stir zone, which subsequently decreases the mechanical properties of the weldments.

Effect of Al2O3 particle content on microstructure and mechanical properties of 1060Al/Al–Al2O3 composites fabricated by cold spraying and accumulative roll bonding

1060Al/Al–Al2O3 laminated particle-reinforced aluminum matrix composites (LPRAMCs) were successfully prepared using a combination of cold spraying (CS) and accumulative roll bonding (ARB) techniques, exhibiting a synergistic improvement in strength and plasticity. The effects of Al2O3 particle content on the microstructure, tensile properties and fracture morphology of LPRAMCs were studied. The results showed that compared with the 1# composites with higher Al2O3 particle content (20.1 vol%), the 2# composites with lower Al2O3 particle content (8.4 vol%) exhibited delayed necking fracture during the ARB process, with greater elongation (El) but lower ultimate tensile strength (UTS). After 5 passes of ARB, the UTS and El of the 1# and 2# composites were 345 MPa, 16.1%, and 293 MPa, 22.2%, respectively. This suggests that the mechanical properties of the Al–Al2O3 deposited layer have a significant impact on the mechanical properties of LPRAMCs. With an increase in ARB passes, the fracture mode of the LPRAMCs shifted from brittle to ductile fracture, displayed by equiaxed and shear dimples. These findings can provide novel insights and theoretical foundations for optimizing the mechanical properties of Al matrix composites.

Preparation and characterization of drug-loaded, electrospun nanofiber mats formulated with zein or zein-based mixtures for wound healing applications.

Electrospun zein mats are known to have poor mechanical and water uptake properties limiting their usefulness as wound dressings.&#x0D; In this study, the effects of the solvent system used, the incorporation of the polymeric additives; polyethylene glycol 20000 (PEG20K) and polyvinylpyrrolidone K30 (PVPK30); and the crosslinking agent Tannic Acid (TA) on the mechanical and water uptake characteristics of zein – based nanofiber mats were investigated.&#x0D; The incorporation of either PEG20K or PVPK30 resulted in an improvement in water vapor sorption and a reduction in water contact-angle of the nanofiber mats. In addition, the incorporation of PEG20K and PVPK30 reduced the ultimate tensile strength, and Young’s modulus while increasing the percent elongation of the nanofiber mats. The use of tannic acid as a crosslinking agent led to an increase in the water vapor sorption, ultimate tensile strength, and Young’s modulus of the nanofiber mats.&#x0D; Mats with smaller average fiber diameter, greater ultimate tensile strength, higher Young's modulus, and greater water vapor sorption were obtained when using 80% (v/v) aqueous ethanol as a solvent system during the preparation of the nanofiber mats when compared to those produced using 60% (v/v) aqueous ethanol. In addition, using solutions with lower zein concentration resulted in mats with lower average fiber diameter, lower ultimate tensile strength and Young’s modulus, and higher percent elongation.&#x0D; Selected formulations were loaded with tetracycline hydrochloride and drug release was evaluated in bulk liquid and using Franz diffusion cells. The use of Franz diffusion cells allowed the discrimination between formulation performance as a function of composition and water uptake properties. Drug release from nanofiber mats was also confirmed by observing the formation of an inhibition zone in cultures of E. coli and S. aureus using the agar diffusion assay.&#x0D; Improved performance of zein nanofiber mats was achieved using polymeric modifiers and crosslinking with tannic acid improving their suitability for wound dressing applications.

Microstructural Characterization and Mechanical Properties of Metastable Beta and α+β Titanium Alloy Electron Beam Weldments

In the present study, the microstructural and mechanical properties of Ti-15V-3Cr-3Al-3Sn (Ti-1533) and Ti-6Al-4V (Ti-64) electron beam welds have been studied. Optical microscopy investigations revealed the presence of three different zones, namely, the fusion zone (FZ), the heat-affected zone (HAZ), and the base metal (BM). In Ti-1533 weld, the BM comprises equiaxed β grains while the FZ consists of large columnar β grains. Further, the HAZ constitutes coarse equiaxed β grains near the FZ. However, in the case of Ti-64 weld, the BM comprises a slightly elongated α phase and transformed β phase while the FZ consists of an acicular martensitic phase. Welds prepared with Ti-1533 exhibit a lower ultimate tensile strength (UTS) of 726 ± 5 MPa, yield strength (YS) of 702 ± 5 MPa, and % elongation (%El) of 12 compared to its BM (YS: 738 ± 5 MPa; UTS: 778 ± 5 MPa; %El: 15). The lower strength in Ti-1533 weld is due to the presence of coarse columnar β grains in the FZ while Ti-64 weld exhibits superior tensile properties (UTS: 993 ± 5 MPa; YS: 959 ± 4 MPa; %El: 9) compared to its BM (UTS: 910 ± 5 MPa; YS: 856 ± 5 MPa; %El: 14). The higher strength for Ti-64 weld could be attributed to the formation of acicular martensitic α′ in the FZ. However, Ti-64 welds subjected to postweld heat treatment (PWHT) showed a decrease in strength (UTS: 922 ± 4 MPa; YS: 858 ± 4; %El: 12) compared to as-welded Ti-64 welds. This is attributed to the formation of the diffusional product α+β phase in the FZ. In contrast, Ti-1533 welds subjected to PWHT showed a rapid increase in tensile property (UTS: 1224 ± 6MPa; YS: 1205 ± 8; %El: 9) values and hardness (380 HV) values compared to as-welded Ti-1533 welds. This increase in strength after PWHT is due to uniform precipitation of alpha particles in the β matrix, which was evidenced by transmission electron microscope results.

Mechanical and Thermal Properties of the High Thermal Conductivity Steel (HTCS) Additively Manufactured via Powder-Fed Direct Energy Deposition

High thermal conductivity steel (HTCS-150) is deposited onto non-heat-treated AISI H13 (N-H13) via powder-fed direct energy deposition (DED) based on the response surface methodology (RSM) to enhance the mechanical properties and thermal conductivity of N-H13, which is generally used as a hot-work tool steel. The main process parameters of the powder-fed DED are priorly optimized to minimize defects in the deposited regions and, therefore, to obtain homogeneous material properties. The deposited HTCS-150 is comprehensively evaluated through hardness, tensile, and wear tests at the different temperatures of 25, 200, 400, 600, and 800 °C. Compared to conventionally heat-treated (quenched and tempered) H13 (HT-H13), the hardness of the additively manufactured HTCS-150 slightly increases at 25 °C, whereas it does not show any significant difference above 200 °C. However, the HTCS-150 deposited on N-H13 shows a lower ultimate tensile strength and elongation than HT-H13 at all tested temperatures, and the deposition of the HTCS-150 on N-H13 enhances the ultimate tensile strength of N-H13. While the HTCS-150 does not show a significant difference in the wear rate below 400 °C compared to HT-H13, it shows a lower wear rate above 600 °C. The HTCS-150 reveals a higher thermal conductivity than the HT-H13 below 600 °C, whereas the behavior is reversed at 800 °C. The results suggest that the HTCS-150 additively manufactured via powder-fed direct energy deposition can enhance the mechanical and thermal properties of N-H13, including hardness, tensile strength, wear resistance, and thermal conductivity in a wide range of temperatures, often superior to those of HT-H13.

Optimization of FSW parameters for enhancing dissimilar joint strength of AA7050 and AA6061 using Response Surface Methodology (RSM)

This study used a central composite design of RSM to friction stir welding (FSW) of two different Al-alloys, AA6061 and AA7050, by varying input parameters, including tool tilt angle (TTA), rotating tool speed (TRS), and welding speed (WS). Twenty experiments were performed, and output responses such as UTS, percent strain, and hardness were perceived. The FSW parameters were optimized using the desirability method. An analysis of variance was performed with a 95 percent confidence interval (CI) to assess the suitability of the produced model. This study found that the WS and TRS were the most crucial variables affecting the ultimate tensile strength (UTS) and hardness of the weldments. At a TRS of 1500 rpm, 150 mm/min, and a TTA of 2°, the highest UTS (255.83 MPa) and percent strain (21.02) were recorded. At a WS of 120 mm/min, a TTA of 2°, and a TRS of 1100 rpm, the lowest UTS (148.58 MPa) and hardness value (66.4HV) were noted. The results of the tensile test demonstrate the significance of the TRS and WS in affecting the UTS of the welded joint. A higher TRS causes more significant material consolidation behind the shoulder and improved mechanical properties.

The influence of strain rate and annealing heat treatments on the corrosion and mechanical properties of WE43 and Zn7Ag biodegradable wires for application in soft tissue reconstructions

This study investigated the influence of annealing heat treatments on the microstructure, corrosion and mechanical behaviour of wires made from the Mg alloy WE43 and the Zn alloy Zn7Ag. The applied strain rate had little influence on the mechanical properties of WE43, whereas decreasing strain rate decreased the strength and increased the ductility of Zn7Ag attributed to creep. The annealing heat treatments had (i) a small influence on the corrosion rate of both WE43 and Zn7Ag wires, (ii) little influence on the mechanical properties of WE43, and (iii) had little influence on the strength of Zn7Ag but tended to decrease ductility and eliminated strain softening. WE43-FA immersed in Zahrina's interstitial fluid (ZIF) for 12 days had a yield strength that was decreased somewhat but fracture occurred much earlier causing a lower ductility and a lower ultimate tensile strength, attributed to notch sensitivity. Zn7Ag after 12 days and 20 days exposure to ZIF showed some reduction in the yield stress, and also early onset of fracture leading to a large decrease in ductility and some decrease in the ultimate tensile strength, also possibly attributed to notch sensitivity.

Development of an accurate “composition-process-properties” dataset for SLMed Al-Si-(Mg) alloys and its application in alloy design

Al-Si-Mg series alloys are the most common alloys available for additive manufacturing forming with low cracking tendency. However, there is no systematic study on the computational design of SLMed Al-Si-(Mg) alloys due to the huge parameter space of composition and processes. In this paper, a high-quality dataset of SLMed Al-Si-(Mg) alloys containing 176 pieces of data from 50 publications was first established, which recorded the information, including alloy compositions, process parameters, test conditions, and mechanical properties. A threshold value of 35 J/mm3 for energy density (Ed) was then proposed as a criterion to clean the data points with lower ultimate tensile strength (UTS) and elongation (EL). The cleaned dataset consists of a first training/testing dataset with 142 data for model construction and a second testing dataset with 9 data for model verification. After that, four machine learning models were applied to establish the quantitative relation of “composition-processes-properties” in SLMed Al-Si-(Mg) alloys. The MLPReg model was chosen as the optimal one considering its best performance and subsequently utilized to design novel compositions and process parameters for SLMed Al-Si-(Mg) alloys. The UTS and EL of the designed alloy with a maximum comprehensive mechanical property are 549 MPa and 16%, both of which are higher than all the available experimental data. It is anticipated that the present design strategy based on the machine learning method should generally be applicable to other SLMed alloy systems.

Quenching of Carbon Steel Plates with Water Impinging Jets: Differential Properties and Fractography

The demand for steel components with tailored properties is constantly growing. To obtain a specific variation of microstructures and mechanical properties along the component it must undergo a controllable cooling. One way to control the cooling rates along the component is by using different simultaneous water jet impingements on a hot austenitized surface. This can be done by a newly developed test rig for water Impinging Jet Quenching Technique (IJQT). This work discusses the effect of IJQT on mechanical properties and fracture behavior of 15 mm steel plates containing 0.27 and 0.38 mass-% carbon. The samples were cooled in a specifically designed setup of the technique to obtain simultaneous water and air cooling resulting in diverse microstructures. The mechanical property gradients of both steels were analyzed through hardness measurements and tensile tests. The fracture surfaces and the near fracture regions were observed using scanning electron microscope and light optical microscope respectively.The results from tensile tests showed that the larger part of the sample with higher carbon content was fully hardened, however smoothly transitioning to a more ductile region. The sample with lower carbon content combined various degrees of hardening and transitioned from higher to lower ultimate tensile strength values. Fracture behavior of higher carbon steel was predominantly brittle transitioning to a ductile, while the lower carbon steel had a small region showing brittle fracture transitioning to a larger region of predominant ductile fracture behavior.