Higher Ultimate Tensile Strength Research Articles

Influence of Post-Weld Heat Treatment on Mechanical Properties and Microstructure of Plasma Arc-Welded 316 Stainless Steel

This study investigates the effects of post-weld heat treatment (PWHT) on the microstructures and mechanical properties of plasma arc-welded 316 stainless steel. The experimental parameters included the solid solution temperatures of 650 °C and 1050 °C, solid solution durations of 1 h and 4 h, and quenching media of water and air. The mechanical properties were evaluated using Vickers hardness testing, tensile testing, scanning electron microscopy (SEM), and optical microscopy (OM). The highest ultimate tensile strength (UTS) of 693.93 MPa and Vickers hardness of 196.4 in the welded zone were achieved by heat-treating at 650 °C for one hour, quenching in water, and aging at 500 °C for 24 h. Heat-treating at 650 °C for one hour, followed by quenching in water and aging at 500 °C for 24 h results in larger dendritic δ grains and contains more σ phase compared to the other conditions, resulting in increased strength and hardness. Additionally, it shows wider and shallower dimple structures, which account for its reduced impact toughness.

Investigation of the mechanical properties of lead-free Sn-58Bi solder alloy with cobalt addition through flux doping

Purpose This study aims to investigate the effect of incorporating cobalt (Co) into Sn-58Bi alloy on its phase composition, tensile properties, hardness and thermal aging performances. The fracture morphologies of tensile-tested solders are also investigated to correlate the microstructural changes with tensile properties of the solder alloys. Then, the thermal aging performances of the solder alloys are investigated in terms of their intermetallic compound (IMC) layer morphology and thickness. Design/methodology/approach The Sn-58Bi and Sn-58Bi-xCo, where x = 1.0, 1.5 and 2.0 Wt.%, were prepared using the flux doping technique. X-ray diffraction (XRD) is used to study the phase composition of the solder alloys, whereas scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) are used to investigate the microstructure, fractography and compositions of the solders. Tensile properties such as ultimate tensile strength (UTS), Young’s modulus and elongation are tested using the tensile test, whereas the microhardness value is gained from the micro-Vickers hardness test. The morphology and thickness of the IMC layer at the solder’s joints are investigated by varying the thermally aging duration up to 56 days at 80°C. Findings XRD analysis shows the presence of Co3Sn2 phase and confirms that Co was successfully incorporated via the flux doping technique. The microstructure of all Sn-58Bi-xCo solders did not differ significantly from Sn-58Bi solders. Sn-58Bi-2.0Co solder exhibited optimum properties among all compositions, with the highest UTS (87.89 ± 2.55 MPa) at 0.01 s−1 strain rate and the lowest IMC layer thickness at the interface after being thermally aged for 56 days (3.84 ± 0.67 µm). Originality/value The originality and value of this research lie in its novel exploration of the flux doping technique to introduce minor alloying of Co into Sn-58Bi solder alloys, providing new insights into enhancing the properties and performance of these solders. This new Sn-Bi-Co alloy has the potential to replace lead-containing solder alloy in low-temperature soldering.

Mechanical property and strengthening mechanism of ZrC nanoparticle dispersion-strengthened Mo containing FeCrAl alloys

Poor mechanical strength at high temperature is the key problem to limit the application of FeCrAl alloys as the candidates for the accident tolerant fuel (ATF) cladding in LWRs. Fe-13Cr-5Al (wt%) alloys were strengthened by adding solid solution element Mo and nanosized ZrC particles, and the strengthening mechanism was assessed by microstructure characterizations including TEM and EBSD. Fe-13Cr-5Al-2Mo-1ZrC alloy has the highest ultimate tensile strength (UTS) and an acceptable ductility at each tested temperature (Room temperature, 400°C or 800°C). Especially at 800 °C, the UTS of Fe-13Cr-5Al-2Mo-1ZrC alloy is about 124 MPa, which is 125% and 34.7 % higher than that of raw Fe-13Cr-5Al (55 MPa) and Fe-13Cr-5Al-1ZrC alloys (89 MPa), respectively. Fe-13Cr-5Al-2Mo-1ZrC alloy has the highest hardness of 306.3 HV, which is 12.8% higher than that of Fe-13Cr-5Al and 3.7% higher than that of Fe-13Cr-5Al-1ZrC alloys, respectively. Furthermore, Fe-13Cr-5Al-2Mo-1ZrC samples maintain high strength and favorable ductility after annealing at 1000°C for 20 h indicating their superior thermal stabilities. The excellent mechanical properties and superior thermal stabilities of Fe-13Cr-5Al-2Mo-1ZrC alloy were not only attributed to the dispersion strengthen by nanosized ZrC particles, the solid solution strengthening by Mo elements, but also the grain refinement structure promoted by the synergistic effects of Mo and ZrC additions.

Experimental analysis of hybrid AM60 magnesium composites reinforced with TiC and TiB2 via stir casting

Rapid progress was made in the development of additive manufacturing process, which went commencing being uncomplicated model substitutes to talented additive process. With powders, additive method such as full melting, segment by segment material fusion, and congeal of fine particles may present inimitable opportunities and compensation. Titanium carbide (TiC) and titanium diboride (TiB2) are employed as reinforcements in the creation of AM60-based hybrid metal matrix magnesium composites. Hybrid AM60 nanocomposites were made using well-known additive manufacturing techniques such selective laser melting. The AM60 bar was created from cylindrical type specimens. The reinforcements are increased by percentages two combination of hybrid composites are prepared AM60 with 4 % Titanium carbide (TiC) and titanium diboride (TiB2) and 8 % Titanium carbide (TiC) and titanium diboride (TiB2). Consequences of the reinforcement were evaluated using micro tensile and micro hardness tests. Among the samples and specimens are showed in harmony through ASTM values, micro tensile and micro hardness characteristics are evaluated using Digital tensometer instrument and a Vickers hardness tester. Vickers Hardness Numbers (VHN) for AM60 magnesium alloy with 4, and 8 % reinforcing are 185.9, and 206.8, respectively. The highest ultimate tensile strengths are, respectively, 703.15, and 809.9 MPa. An Optical Micrograph is used to evaluate the bonding structure of composites, while a Field Emission Scanning Electron Microscope (FESEM) is used to evaluate micro tensile specimens. The greater impact of the different reinforcements Titanium carbide (TiC) and titanium diboride (TiB2) has led to more improved tensile and hardness properties.

Mechanical properties and corrosion resistance improvement of TiAlSnMo alloys via Mo addition

In this paper, Ti-5Al-2.5Sn-xMo (TASxM, x = 0,5,10,15 wt%) alloys were designed and prepared. Phase compositon and microstructure analysis results indicate that the addition of Mo reduces the phase transition point of TASxM alloys, stabilizes more β phase to room temperature, and refines the α grains. The strength of the TASxM alloys exhibits a positive correlation with the increasing Mo content within 10 wt%, and the highest ultimate tensile strength (UTS) can be obtained in TAS10M (1260 MPa), which can be primarily attributed to the synergistic effects of phase transition, solid solution strengthening, and fine grain strengthening. Interestingly, the UTS of TAS15M unexpectedly decreases to 724 MPa, which is strongly influenced by the altered slip system numbers resulting from the β/α phase ratio. Even more intriguing is the observation of stress-induced martensitic transformation in the deformed TAS15M alloy, often resulting in a substantial influence on elongation. The corrosion resistance of the TASxM alloy has also been investigated through electrochemical experiments. The findings reveal that the corrosion resistance of the TASxM alloy is enhanced with the elevation of Mo content, peaking at TAS15M. This improved resistance is attributed to the augmented β phase content and the formation of protective MoO2 and MoO3 oxide films on the surface of alloy.

Adhesive and healable supramolecular comb-polymers

A series of supramolecular comb polymers (SCPs) with adhesive and healable characteristics have been generated through the copolymerisation of methacrylate monomers featuring aromatic amide functionalities with lauryl methacrylate. By varying the amide functionality and loading of the supramolecular monomers, the properties of the resulting SCPs can be tailored, ultimately providing stable films at room temperature. As the loading of the amide-bearing monomer was increased, the phase separation between the hard and soft domains was enhanced, promoting larger hard-domain aggregation, as observed via atomic force microscopy (AFM). The mechanical properties of the SCPs correlated to the loading of the amide-bearing monomers, by increasing the mol% incorporation the resulting SCPs transition from possessing high strain to high ultimate tensile strength (UTS) and Young's modulus (YM). Over several re-adhesion cycles, the SCPs were shown to retain their shear strength when thermally adhered to both glass and aluminium substrates. Additionally, the SCPs exhibited healable properties at elevated temperatures (> 45 °C) allowing for the recovery of mechanical properties post-damage.

Effect of partitioning treatment on the strengthening and plasticising mechanism of one-step quenching and partitioning steels

The effects of partitioning temperature and time on the strengthening and plasticising mechanism of a one-step quenching and partitioning (Q&P) steel were investigated. The results show that as the partitioning temperature decreased, the lath martensite became finer with higher dislocation density, while the dislocation density and RA amount decreased with increasing partitioning time. Lower quenching temperature and shorter partitioning time are conducive to achieve the high ultimate tensile strength of 1377 MPa and the better total elongation of 12.3% for low-carbon one-step Q&P steels. Meanwhile, the dislocation strengthening caused by martensite and the solid solution strengthening are main strengthening mechanisms of one-step Q&P steels. In addition, a new martensite transformation kinetic model considering the influence of silicon element was established, and simultaneously, the modified CCE model predicted RA fractions more accurately for high-silicon Q&P steels, especially at lower quenching temperature.

Исследования соединений AA7075, сваренных трением с перемешиванием и ультразвуковым воздействием: механические свойства и анализ разрушения

Introduction. Joint efficiency and strength, particularly in aluminum alloys, are crucial in aerospace, defense, and industrial applications. Post-welding treatments like shot peening and laser shock peening significantly improve joint efficiency and strength, enhancing fatigue life, grain structure, and tensile strength. The purpose of the work. The literature reviewed shows that the ultrasonic vibration-assisted friction stir welding (UVaFSW) and post-weld treatment improved the mechanical properties and material flow. However, limited studies have been observed on the UVaFSW joints of AA7075-T651, considering the consequence of welding speed, tool rotation, and post-weld shot peeing treatment. The methods of investigation. The study investigates the ultrasonic vibration-assisted friction stir welded (UVaFSwed) AA7075-T651 joint's tensile strength, microhardness, microstructure, and fracture behavior, considering the impact of tool rotation, welding speed, and post-weld shot peening treatment. Results and Discussion. The post-weld treated shot-peened UVaFSWed joints demonstrated the maximum tensile strength of 373.43 MPa, the microhardness of 161 HV, and the lowest surface roughness of 15.16 µm at 40 mm/min welding speed when compared to the friction stir-welded (FSWed) joints. These results indicate that shot peening improved the mechanical properties and surface quality of the UVaFSWed joints. The high tensile strength and low surface roughness make these joints suitable for applications requiring strength and aesthetics. The fracture for the shot peened UVaFSWed joints mainly occurred in the heat-affected zone (HAZ) during the tensile test. It could be attributed to the higher temperature experienced during welding, which resulted in grain growth and decreased material strength in the HAZ. The shot-peened UVaFSWed joint has a more uniform grain distribution than the FSWed one, which contributed to the joint's higher tensile strength. The fractured surface of the shot peened UVaFSWed joints showed larger, equiaxed, and shallow dimples, resulting in higher ultimate tensile strength (UTS) and microhardness compared to the conventional FSWed joints. The mechanical properties and microstructure observed in the welding zones of shot peened UVaFSWed joints are superior to those of conventional FSW joints. However, further investigation is required to determine the specific factors contributing to this localized failure at HAZ, considering the effects of shot peening parameters. This study also suggests the potential for optimizing shot peened UVaFSWed joints of AA7075-T651.

Microstructural evolution and cryogenic and ambient temperature deformation behavior of the near-α titanium alloy TA15 fabricated by laser powder bed fusion

Titanium alloys produced by additive manufacturing show excellent mechanical properties at room temperature. However, their deformation behavior at low temperature is still not fully understood. In this study, the microstructural evolution and tensile behavior of the near-α titanium alloy Ti-6.5Al-2Zr-Mo-V (TA15), fabricated via laser powder bed fusion (LPBF), were determined at both 25 °C and −196 °C. The LPBFed TA15 alloy shows the microstructure of α laths and acicular α′ martensite due to the rapid cooling rate during LPBF processing. Pyramidal <c+a> slip and numerous twins, including nano-twins and triple twins, were activated at cryogenic temperature, leading to the high ultimate tensile strength (UTS) up to 1750±8 MPa and yield strength (YS) up to 1548±25 MPa, which is higher than the strength at room temperature (YS∼1103 MPa, UTS∼1281 MPa). The dominant deformation mechanism changes from dislocation slip to twinning with decreasing temperature, leading to uniform deformation with an elongation of 5.2±0.1 %. The results can guide the control of the microstructure of LPBFed near-α titanium alloys at cryogenic temperature.

Microstructures and mechanical properties of additively manufactured Fe–21Mn-0.6C TWIP steel using laser powder bed fusion

Twinning induced plasticity (TWIP) high manganese steel exhibits high ultimate tensile strength (UTS) and ductility, but its low yield strength restricts its applications. This research presents a Fe–21Mn-0.6C TWIP steel with enhanced mechanical properties additively manufactured using laser powder bed fusion (LPBF). The average grain size of the LPBF-fabricated Fe–21Mn-0.6C was 17.1 μm in the vertical direction, which was a quarter of that of a wrought one. The tensile yield strength was 657 MPa and the UTS was 1089 MPa with an elongation of 47.9% for the vertical direction. Compared to the wrought Fe–21Mn-0.6C, the yield strength increased by 110%. The high strength of LPBF-fabricated Fe–21Mn-0.6C is primarily attributed to solution, grain boundary and dislocation strengthening. Serrations were observed in the stress-strain curves at the initial stage of deformation, showing large stress drops. In the annealed sample, serrations appeared at a later stage of deformation with little stress drops. This difference in serration phenomenon is attributed to the varying dislocation density in the two samples.

High strength and ductility high-entropy intermetallic matrix composites reinforced with in-situ hierarchical TiB2 particles

The design guided by entropy enables the attainment of superior mechanical properties and further extends the concept of high-entropy alloys to intermetallic systems, thus forming high-entropy intermetallic compounds and even high-entropy intermetallic matrix composites. In this study, a novel high-entropy intermetallic matrix composites incorporating in-situ hierarchical TiB2 particles was successfully synthesized through the spark plasma sintering. This method enables precise control over the microstructure, ensuring uniform distribution of the in-situ formed TiB2 particles within the high-entropy intermetallic matrix. The in-situ formation of TiB2 particles is achieved through a reactive sintering mechanism, which not only contributes to the composite's enhanced mechanical properties but also ensures excellent bonding between the precipitates and intermetallic matrix. The composites were composed of the ordered L12 intermetallic matrix and the hierarchical hexagonal-close-packed TiB2 particles. Due to the L12 intermetallic matrix and the heterogeneous distribution of TiB2 reinforcement, the intermetallic matrix composites demonstrate a high ultimate tensile strength of ∼1400 MPa. The TiB2 play a pivotal role in impeding the propagation of cracks and the collaborate with distinctive disordered interfaces at grain boundaries, ensuring enough ductility. The disordered interfaces, exhibiting an average width in the range of 5 nm–10 nm, possess the capability to delay fracture and promote the strain-hardening rate during plastic deformation. The intermetallic matrix composites overcome the limitations typically associated with conventional intermetallics and offer an excellent strength and ductility balance. These findings are expected to formulate additional strategies for designing in-situ reinforcement-strengthened high-entropy intermetallic matrix composites with exceptional mechanical properties.

Microstructure Evolution and Strengthening Mechanism of Dual-Phase Mg-8.3Li-3.1Al-1.09Si Alloys during Warm Rolling.

In this study, the rolling process of the warm-rolled duplex-phase Mg-8.3Li-3.1Al-1.09Si alloy and the strengthening mechanism of as-rolled Mg-Li alloy were investigated. The highest ultimate tensile strength (UTS, 323.66 ± 19.89 MPa) could be obtained using a three-pass rolling process with a 30% thickness reduction for each pass at 553 K. The strength of the as-rolled LAS831 alloy is determined by a combination of second-phase strengthening, grain refinement strengthening, dislocation strengthening, and load-transfer reinforcement. Of these factors, dislocation strengthening, which is caused by strain hardening of the α-Mg phase, can produce a good strengthening effect but also cause a decrease in plasticity. The Mg2Si phase is broken up into particles or strips during the rolling process. After three passes, the AlLi particles were transformed into an AlLi phase, and the Mg2Si particles and nanosized AlLi particles strengthened the second phase to form a hard phase. The average size of the DRXed β-Li grains decreased with each successive rolling pass, and the average size of recrystallized grains in the three-pass-rolled LAS831 alloy became as low as 0.27 μm. The interface between the strip-like Mg2Si phase and the α-Mg phase is characterized by semicoherent bonding, which can promote the transfer of tensile and shear forces from the matrix to the strip-like Mg2Si phase, thereby improving the strength of the matrix and thus strengthening the LAS831 alloy.

Synergistic effects of chemical composition on precipitates, dislocations, and mechanical properties of precipitation-strengthened alloys

The properties of materials are intricately dependent on their chemical composition, and microstructures. Achieving a precise modulation in the composition and microstructure of materials to enhance properties significantly is a huge challenge. In this work, we uncovered the effects of nickel and silicon composition on the precipitates, dislocations, and properties of Cu–Ni–Si alloys. The results show that the volume fraction of precipitates increased from 0.84 % to 4.80 % with the increase of Ni and Si contents. The average diameter of the precipitates increased from 6.20 nm to 20.21 nm, and the dislocation density increased from 2.16 × 1013 m−2 to 4.08 × 1015 m−2 concerning the Ni and Si contents. In addition, the dislocation type changes from half-edge dislocation and half-screw dislocation to screw dislocation. The modified WHWA (Williamson Hall-Warren Averbach) method was proved to be the most accurate way of calculating dislocation density. As anisotropy was present in the alloy, adding a dislocation contrast factor and removing some lower-intensity diffraction peaks could further correct the obtained results and reduce the calculation error. Furthermore, the above analysis and findings were employed to design a Cu-3.21Ni-0.66Si alloy with a high yield strength (814 MPa), high ultimate tensile strength (970 MPa), and comparable electrical conductivity of 42.4 % IACS. This work offers a meaningful way to develop precipitation-strengthening alloys.

Effects and molecular mechanisms of jet ablation and fuel corrosion on separation failure of the asphalt-aggregate interface in airport asphalt pavements

To guide the improvement of asphalt pavement durability in airports, the effects and molecular mechanisms of jet ablation and fuel corrosion on separation failure of the asphalt-aggregate interface were investigated in this study using molecular dynamics simulations and density functional theory method. Firstly, tensile separation behaviors of the virgin, aged, and fuel-corroded asphalt-aggregate interfaces were simulated under different loading rates to evaluate their tensile strength and fatigue cracking resistance, and the experimental data were also used to verify the reliability of the simulation results. Subsequently, the molecular mechanisms of jet ablation and fuel corrosion on the separation failure of the asphalt-aggregate interface were analyzed by calculating the work of adhesion, work of cohesion, flowability parameters, and intermolecular binding energy. The results show that the aged specimen has higher ultimate tensile strength and fracture energy, but its flexibility and fatigue cracking resistance are significantly reduced. This is because the polar oxygen-containing groups generated during high-temperature aging enhance the intermolecular binding energy of the asphalt, but this also restricts the diffusion of asphalt molecules, resulting in greater frictional resistance and viscosity of asphalt during shear deformation, and thus loss of mobility and self-healing properties. On the contrary, since the light and medium oils soften and dilute the asphalt, and also weaken the intermolecular binding energy of asphalt, the fuel corrosion reduces the ultimate tensile strength and fracture energy of the asphalt-aggregate interface system, resulting in insufficient overall strength and load-bearing capacity.

A high-strength binary Mg-1.2Ce alloy with ultra-fine grains achieved by conventional one-step extrusion during 300–400 °C

Ultra-fine grained magnesium alloys are usually prepared by severe deformation and medium-low temperature deformation. In this work, it has been found that the binary Mg-1.2Ce alloy with the uniform distributed Mg12Ce precipitates smaller than 3 μm is a good candidate to obtain ultra-fine grains by conventional one-step extrusion at high temperatures. All the three Mg-1.2Ce samples extruded at 300 °C, 350 °C and 400 °C show a bimodal microstructure with high-density dislocations, whose average grain sizes are 1.19 ± 0.92 μm, 1.32 ± 1.30 μm, and 1.44 ± 1.33 μm, respectively. A linear relation of ln(d) = -0.05ln(Z)+1.27 was determined relating the average grain size (d) to the Zener-Hollomon parameter (Z). The alloy extruded at 300 °C exhibits an exceptionally high ultimate tensile strength (UTS) of 412.3 ± 5.3 MPa and yield strength (TYS) of 387.6 ± 3.2 MPa, but a low elongation after fracture (El) of 4.9 ± 0.8 %. With the extrusion temperature increasing, the tensile strength gradually decreases. For the 1.2E-400 sample, the TYS and the UTS drop to 347.2 ± 2.1 MPa and 349.4 ± 2.8 MPa, while the El increases to a more acceptable value of 12.6 ± 1.4 %. The microstructure analysis reveals that Ce atoms segregate along grain boundaries and dislocations in the Mg-1.2Ce alloy, which can limit the gliding of GBs or the slipping and climbing of dislocations. Additionally, dislocations can be pinned by Mg12Ce precipitates, thereby also restricting dislocation and grain boundary mobility. Consequently, the dynamic recrystallization (DRX) process is delayed, leading to the formation of a bimodal microstructure.

Microstructure, mechanical and electrical properties of a novel low-cost high-strength Pt-xAu-5Ni alloy

The present study designed and prepared a novel platinum alloy system Pt-xAu-5Ni (x = 0, 2, 5, wt.%) with high strength and good electrical resistivity. The mechanical, electrical properties and related microstructure during the cold deformation and subsequent aging process were investigated. The cold-deformed Pt–5Ni alloy obtained the yield strength of 581 MPa, the ultimate tensile strength of 828 MPa, the hardness of 283 HV, and the electrical resistivity of 23.9 μΩ⋅cm. The subsequent aging process and the Au addition into Pt–5Ni alloy were found to both enhance the mechanical properties. Therefore, with the dual strengthening effect of the subsequent aging and the Au addition, Pt–5Au–5Ni alloy achieved the high yield strength of 889 MPa, the high ultimate tensile strength of 1117 MPa, the high hardness of 361 HV with the electrical resistivity of 26.7 μΩ⋅cm. The precipitation of L12-type Pt3Ni nanoparticles and L11-type CSRO dominated the age-strengthening behavior of Pt–2Au–5Ni and Pt–5Au–5Ni alloys after cold deformation. The Au addition refined the grains via the experimental observations, and predictably favored the L12-type Pt3Ni nanoprecipitation based on the thermodynamical calculations, thus the Au addition effectively strengthened Pt–5Ni alloy. This study provides a novel platinum alloy system with excellent mechanical and electrical properties, which has potential application in the electrical contact field.

Exceptional combination of mechanical properties and cavitation erosion-corrosion resistance in a Fe23.7Co23.8Ni23.8Cr23.7Mo5 multi-principal element alloy

This study analyzed cavitation erosion (CE) and cavitation erosion-corrosion (CE-C) of single-phase face-centered cubic structured Fe23.7Co23.8Ni23.8Cr23.7Mo5 multi-principal element alloy (MPEA) with varying grain sizes obtained through post-deformation annealing (PDA). The average grain sizes of the samples after annealing at 1100 °C for 60 s, 1150 °C for 60 s, and 1100 °C for 200 s are 4.1 µm, 10.3 µm, and 15.2 µm, respectively. Among them, the 4.1 µm sample exhibits the best combination of high ultimate tensile strength (889 MPa) and large elongation (40.3%), as well as good electrochemical corrosion resistance in NaCl solution. Under the conditions of CE and CE-C for a duration of 10 h, the 4.1 µm specimen exhibits cumulative mass losses of approximately 1.4 mg and 2.6 mg, respectively. In contrast, under identical conditions, the 316 L SS registers cumulative mass losses of approximately 16.7 mg and 24.8 mg, respectively. Due to the excellent mechanical properties and work hardening ability of the 4.1 µm sample, it can effectively resist the plastic deformation caused by cavitation erosion, reducing mass loss. In addition, the stable passivation film enhances its resistance to Cl- destruction, thus demonstrating notable corrosion resistance. Ultimately, under conditions where cavitation erosion and corrosion coexist, these combined properties enable the 4.1 µm sample to exhibit the least mass loss and damage.

The Tensile Properties of Functionally Graded Materials in MSLA 3D Printing as a Function of Exposure Time

Functionally graded additive manufacturing (FGAM) emerged from the combination of Functionally Graded Materials into additive manufacturing. This work involved the production of FGAM specimens to alter the characteristics of both the outer and inner zones of tensile specimens. This was achieved by adjusting the exposure time without additional costs or equipment. During the assessment, the tensile specimen was separated into three zones. The exterior layers were initially created with a 3-second exposure time, followed by the interior layers with a 15-second exposure time. Then, the process was reversed, with the outer layers exposed for 15 seconds and the inner layers exposed for 3 seconds. Subsequently, all layers were generated using exposure durations of 3 seconds and 15 seconds, respectively, without any alterations, resulting in a total of 4 distinct samples. The hardness and tensile tests were conducted on all specimens, both with and without post-curing, in order to assess the impact of post-curing. The outcomes indicate that the levels of hardness and maximum tensile strength rise as the final curing process progresses, but the elongation capability diminishes. The highest ultimate tensile strength, achieved after 15 seconds of exposure time with post cure, was measured at 46.46 ± 0.9 MPa. The green FGAM specimens have a greater ultimate tensile strength (35.85 ± 0.4 MPa) when created with an exposure time of 15-3-15 s. However, the specimen produced with an exposure time of 3-15-3 s demonstrates a higher ultimate tensile strength (38.77 ± 0.7 MPa) following post curing.

Simultaneously improved the strength and ductility of cast Al-3Li-2Cu alloy by Ti addition and heat treatment

This work systematically investigated the impact of minor Ti addition and heat treatment on grain structure, precipitates, precipitate-free zone (PFZ), and the performance of the Al-3Li-2Cu alloy. Minor Ti addition significantly refines the as-cast alloy, leading to a transition from columnar grains to equiaxed grains. The primary Al3Ti phases, with a low mismatch (0.99%) to the matrix, act as heterogeneous nucleation sites for α-Al, while the presence of Ti solutes restricts grain growth. As a result, the average grain size can be refined to 35.2 μm by adding 0.2 wt% Ti. Besides, minor Ti addition affects the corresponding precipitation behavior of the alloy. Detailed TEM observations reveal that the addition of Ti inhibits the growth of δ’(Al3Li) precipitates and the accompanying δ’-PFZ, which should be related to the interaction between Ti solutes and vacancies. Besides, reducing the aging temperature exerts a similar effect. Finally, the 0.2 wt% Ti-modified alloy exhibits excellent mechanical properties after aging at 175 °C for 8 h. It demonstrates a high yield strength (272 MPa), a high ultimate tensile strength (399 MPa), and an acceptable elongation (5.9%), which represent an increase of 8.8%, 34.8%, and 293.3%, respectively, compared to the alloy without Ti addition. The simultaneous improvement in strength and ductility is attributed to the presence of fine and equiaxed grains, high-density and homogenous δ’ precipitates, and a narrow δ’-PFZ. In-depth discussions are provided to elucidate the underlying mechanisms governing the microstructure and mechanical properties.

Explosive weld joint characteristics of Copper-Tantalum via simulation

This report aims to examine the effects of impact velocity, impact depth, and impact orientation on the Cu–Ta weld joint of the explosive welding process via MD simulation. The findings indicate that the residual shear stress in the welded block mostly increases as the impact velocity rises. The bottom Ta block is more severely distorted than the higher Cu block due to the impact direction. During the tensile test, three stress zones can be identified including the low-stress Cu block, the high-stress Ta block, and the medium-stress weld joint in the middle of the samples. The weld joint position is lower than the median line of the welded block. The Cu–Ta welded block with 500 m/s impact velocities had the highest ultimate tensile strength (UTS) value of 6.49 GPa. With increasing impact depth, the atomic strain level, residual shear stress, and weld joint dimensions all noticeably increase. The Cu–Ta welded block with an impact depth of 7.5 Å has the greatest UTS values, measuring 11.65 GPa, because of its well-crystal structure. Changing the impact orientation does not result in a dramatic change in atomic strain. Orientation (001) vs (001) has the highest strain and stress rates. With an impact orientation of (110) vs. (111), the Cu–Ta welded block gets the highest UTS value of 8.03 GPa compared to other orientations.