The long, straight grain boundary of the high-entropy alloy (HEA) produced via laser melting deposition (LMD) is prone to cracking due to unidirectional scanning (single wall). To enhance the competitive growth of columnar grains and improve the overall performance of the alloy, a vertical cross scanning method was employed to fabricate FeCoCrNi HEA (bulk). The influence of grain orientation on the microstructure and mechanical properties of FeCoCrNi-LMD was systematically investigated. Microhardness tests and tensile tests were conducted to assess the mechanical property differences between the single-wall and bulk samples. This study shows that using a single scanning strategy results in monolayer wall grains sized at 129.40 μm, with a max texture strength of 21.29. Employing orthogonal scanning yields 61.15 μm block-like grains with a max texture strength of 11.12. Dislocation densities are 1.084 × 10¹² m⁻² and 1.156 × 10¹² m⁻², with average Schmid factors of 0.471 and 0.416. In comparison to the FeCoCrNi-LMD single wall, the bulk material produced through cross-layer orthogonal scanning exhibited reduced residual stress, weakened anisotropy, and improved mechanical properties. These findings are expected to enhance the potential applications of FeCoCrNi-LMD in various industries.

A new hot forming process of a hot-rolled 2205 duplex stainless/AH36 low-carbon steel bimetal composite (2205/AH36 BC) was proposed in this study, using the Gleeble 3500 thermal-mechanical simulator and hot bending tools. The deformation characteristics of 2205/AH36 BC were studied by hot tensile tests at temperatures from 950 to 1250 °C and strain rates ranging from 0.01 to 1 s⁻¹. The tensile temperature has a great influence on the peak flow stress of the bimetal composite. The main microstructure evolution mechanisms, including dynamic recovery (DRV) and dynamic recrystallization (DRX), changed with the deformation temperatures. The different strain rates and the change of strain rates during the deformation process have an influence on the flow behavior of the bimetal composite. During the hot bending process, qualified parts could be formed successfully without obvious cracks in the interfacial zone. Phase and grain orientation spread (GOS) maps of specimens after hot tensile and forming tests were obtained by the electron backscatter diffraction (EBSD) technique to study the microstructure evolution, respectively. It is found that the effect of the working temperature on microstructure evolution is larger than that of the stacking sequence for 2205/AH36 BC. The considerable geometrically necessary dislocation (GND) accumulation occurs around the interface of 2205/AH36 BC under all imposed working conditions after the hot bending process, due to the interfacial micro-defects and complex stress states.

At present, Al matrix composites (AMCs) have drawn much attention owing to their light weight, high specific strength, high thermal conductivity, and superior excellent wear resistance, which endows them with great potential in the aerospace, automobile and military industries. In this study, AMCs with different Ti contents (0, 5 and 10 vol.%) were prepared by powder metallurgy. During the sintering, Al₃Ti particles were in situ formed in the Al matrix. It was found that the Ti completely reacted with the Al matrix and formed fine in situ Al₃Ti particles in Al-10Ti, while some large Ti-Al₃Ti core-shell formed in Al-5Ti due to the incomplete reaction between the Ti and the Al matrix. Furthermore, the hardness of the composites was significantly improved by the in situ formed Al₃Ti particles, reaching 143.3 HV in Al-5Ti and the highest value at 331.2 HV in Al-10Ti, respectively. The wear resistance of the composites is remarkably enhanced by Al₃Ti particles compared to the unreinforced Al. Al-5Ti has the highest wear resistance among the samples. The wear resistance of the Al-10Ti composite becomes slightly deteriorated compared to Al-5Ti due to the brittle nature of Al₃Ti, which leads to a three-body abrasive wear.

Micro deep drawing (MDD) is a fundamental process in microforming which has wide applications in micro electromechanical system (MEMS) and biological engineering. Titanium possesses excellent mechanical properties and biocompatibility, which makes it a preferred material in micromanufacturing. In this study, eco-friendly and low-cost water-based TiO₂ nanolubricants were developed and applied in the MDD with 40 μm-thick pure titanium foils. The lubricants consisting of TiO₂ nanoparticles (NPs), 10 wt% glycerol, 0.1 wt% sodium dodecyl-benzene sulfonate (SDBS) and balanced water were synthesised in a facile process. The MDD with 40 μm-thick pure titanium was carried out using the lubricants with varying concentrations of 0.5, 1.0 and 2.0 wt%. The results show that the formability of micro cups could be significantly improved when the nanolubricants are applied. Especially, the use of 1.0 wt% TiO₂ nanolubricant demonstrates the best lubrication performance by significantly reducing the final drawing forces, and surface roughness, and the wrinkles by up to 24.2%, 12.55% and 4.82%, respectively. The lubrication mechanisms including the ball bearing and mending effects of NPs on open lubricant pockets (OLPs) and close lubricant pockets (CLPs) areas were then revealed through microstructure observation.

Eutectic high-entropy alloys (EHEAs) exhibit excellent casting properties and comprehensive mechanical performance, making them suitable for fabricating spatial engineering components using additive manufacturing techniques. However, the rapid solidification process also leads to increased internal stress and reduced structural stability in the components. Therefore, this study focuses on the AlFeCoCrNi_2.1 EHEA as the research subject, utilizing laser additive manufacturing to fabricate components and systematically investigating the influence of heat treatment processes on the microstructure and mechanical properties of the components. The research demonstrates that low-temperature heat treatment (700 °C and below) acts as a stress relief-annealing process for the components. The yield strength decreased from 1003.2 MPa to 742.1 MPa. At 900 °C heat treatment, the constraining effect between recrystallized grains and surrounding grains outweighs the dislocation release effect caused by recrystallization, resulting in an increase in dislocation density. The yield strength remained approximately stable at around 730 MPa. High-temperature heat treatment (1100 °C) alters the orientation of phase structures and fragments the two-phase structure through recrystallization, leading to generally stable mechanical properties of the components. The yield strength of the cast components further decreased to 582.6 MPa, while that of the LMD-fabricated parts retained stability at approximately 730 MPa.

To improve the quality of products produced from microforming, various nanolubricants have been applied in the field of micromanufacturing in recent years. In this paper, the effects of glycerol-based lubricant containing TiO₂ NPs (NPs) on micro deep drawing (MDD) of austenitic stainless steel (ASS) SUS301 were studied, and the lubrication mechanism involved was discussed. The MDD experiments were conducted with the SUS301 foils under dry, 1, 2, and 4 wt% TiO₂ NP lubrication conditions. The results show that the use of the TiO₂ nanolubricants can significantly improve the quality of the drawn cups in terms of decreased wrinkling and surface roughness. Besides, the concentration of TiO₂ NPs influences lubricity by reducing friction during the MDD process. The peak drawing force is the lowest when 2 wt% nanolubricant is applied, which drops to 72.54 N from 77.38 N under dry conditions. The micro cup drawn under 2 wt% TiO₂ nanolubricant has the best quality among those obtained under all the lubrication conditions. The lubrication mechanisms are derived from the mending effects of TiO₂ NPs and the formation of thin lubricant films associated with the open lubricant pockets (OLPs) and close lubricant pocket (CLPs) theory in the MDD. The CLPs function as reservoirs that retain lubricants to counteract the load pressure, whereas the OLPs lead to lubricant leakage due to the higher flow resistance. It was found that the lubricant film and NPs are insufficient at a low concentration (1 wt%), while the lubrication performance can be enhanced with increased NP concentration. However, there exist apparent agglomerations on the surface of the produced micro cup when using 4 wt% nanolubricant, which greatly deteriorates the lubricant performance in the MDD process. It is concluded that the lubricant containing 2 wt% TiO₂ NPs demonstrates the best lubrication performance during the MDD of ASS SUS301.