Ao Fu

The microstructural characteristics and precipitate features of titanium matrix composites (TMCs) are critical to tribological performance. In this study, TiCp/TA15 composites were fabricated via laser powder bed fusion (LPBF). The as-built composite was then heat-treated at 750 °C for 2 h to obtain a uniform duplex (α + β) microstructure with enhanced TiC precipitation, which was labeled as HT-750. The influence of the microstructural evolution on the tribological performance was systematically investigated. Compared to the as-built composite, the HT-750 composite exhibited a microhardness increase from 360.2 ± 6.4 HV to 459.2 ± 3.1 HV, a reduction in the friction coefficient from 0.649 ± 0.167 to 0.581 ± 0.111, and a decrease in the wear rate from 8.24 ± 0.44 × 10⁻⁴ mm³/(N·m) to 4.81 ± 0.39 × 10⁻⁴ mm³/(N·m), indicating a significant enhancement in wear resistance. This improvement is primarily attributed to the synergistic strengthening effect of the duplex matrix and TiC particles, which enhanced the load-bearing capability and suppressed surface plastic deformation. During the friction process, the dominant wear mechanisms of as-built and HT-750 composites evolved over time but exhibited distinct differences. The as-built composites were prone to continuous plastic deformation and damage accumulation, resulting in severe delamination, oxidative, and abrasive wear. Conversely, the HT-750 composites demonstrated higher resistance to plastic deformation and crack propagation, effectively mitigating interfacial shear and inhibiting damage evolution, with the wear mechanism being dominated by oxidative wear accompanied by abrasive wear and minor delamination. This work provides deep insights into the wear mechanisms of additively manufactured TMCs.

The hot deformation behavior of Ti-4Zr-6Al-0.6Si-0.5Mo high-temperature titanium alloy was investigated under temperatures of 800–1100 °C, strain rates of 0.001–1 s⁻¹, and a true strain of 0.5. Flow stress curves under different temperatures and strain rates were analyzed, and a constitutive equation that depicts the correlation among flow stress, deformation temperature, and strain rate was established. Processing maps were employed for determining the instability domains as well as optimal hot processing window. The results show that the optimal hot processing window for the alloy is a deformation temperature of 950–1100 °C and a strain rate of 0.001–0.01 s⁻¹. Flow instability occurred within two domains: 800–850 °C at strain rates of 0.1–1 s⁻¹ and 900–1075 °C at strain rates of 0.01–0.1 s⁻¹, where the alloy is prone to cracking, resulting in processing failure.

Titanium matrix composites (TMCs), characterized by low density, high strength, and excellent high-temperature mechanical properties, are becoming preferred materials for key components in aerospace engines. However, conventional casting methods for preparing TMCs often encounter issues such as composition segregation and coarse reinforcement phases, hindering their engineering application. In this study, we fabricated TiC/TC4 titanium matrix composites via hot isostatic pressing (HIP). The composites exhibited room-temperature tensile strength of 1058 ± 8 MPa, yield strength of 958 ± 12 MPa, and total elongation of 17.0 ± 0.5%. Furthermore, the TiC/TC4 composites demonstrated favorable high-temperature mechanical properties, with a tensile strength of about 500 MPa at 600 °C. Investigation into plastic deformation and fracture behavior revealed that at room temperature, tensile cracks initiated predominantly around the reinforcing TiC particles, whereas at high temperatures, cracks primarily originated within the matrix. The strengthening mechanisms of the TiC particle-reinforced TC4 composites included particle strengthening, solid solution strengthening, and load-transfer strengthening. Additionally, the precipitation of nano-acicular secondary α (αs) phases within the β phase during high-temperature tensile deformation was observed, contributing to the superior high-temperature mechanical performance of the composites.

Aqueous Zn‐ion batteries are attractive for large‐scale energy storage due to their inherent safety and low cost. However, their practical application is hindered by the unstable Zn metal anode, caused by uncontrollable dendrite growth and severe hydrogen evolution reaction, which significantly shortens cycle life. In this study, amorphous carbon‐coated CuZn composite powders are synthesized using the tandem plasma‐enhanced powder synthesis method and employed as an interfacial regulator to protect Zn anodes. The dual‐phase CuZn alloy core, with its zincophilic nature, is complemented by an ultrathin amorphous carbon shell that repels unfavorable interfacial water molecules while maintaining efficient Zn‐ion transport. This synergistic core–shell structure effectively enhances cycling performance, especially at high rates, and the full cells demonstrate no obvious capacity decay after 1800 cycles. These findings offer valuable insights into practical interfacial design strategies for Zn stabilization in corrosive aqueous electrolytes.

Aerospace and marine engineering impose higher requirements on mechanical properties and lightweight design of materials. In this work, combining the high mechanical properties of FeCrNi medium entropy alloy (MEA) and the lightweight advantages of lattice structure, four types of high-performance FeCrNi MEA lattice structures (BCC, BCCZ, FCC, and FCCZ) were prepared by selective laser melting (SLM) technology, and their dynamic mechanical properties were systematically characterized via split Hopkinson pressure bar (SHPB) method. The results demonstrate that the FCCZ FeCrNi MEA lattice structure exhibits superior comprehensive performance among the four lattice structures, achieving the highest specific compressive strength of 59.1 MPa·g⁻¹·cm⁻³ and specific energy absorption of 26.3 J/g, significantly outperforming conventional lattice materials including 316L and AlSi10Mg alloys. Furthermore, the finite element simulation and Johnson-Cook (J-C) constitutive model of the dynamic compression process can effectively predict the microstructural evolution and mechanical response of lattice structure, providing critical theoretical guidance for optimizing the design of high-performance lattice structure materials.

In this study, the dissimilar joining of aluminum to high-melting-point alloys, including steel, titanium, and copper, was successfully achieved through hot-dipping. By precisely controlling the dipping temperature at 670 °C and maintaining a dipping time of 5 s, uniform aluminum layers with a thickness of 3–4 mm were successfully formed on the surfaces of high-melting-point alloys. This process enabled effective dissimilar metal joining between Al/steel, Al/Ti, and Al/Cu. Metallurgical bonding at the joining interfaces was achieved through the formation of uniform intermetallic compounds, specifically Fe₄Al₁₃, TiAl₃, Al₂Cu, and Al₃Cu₄, respectively. The different joints exhibited varying mechanical properties: the Al/Cu joint demonstrated the highest shear strength at 79.1 MPa, while the Fe₄Al₁₃-containing joint exhibited the highest hardness, reaching 604.4 HV. Numerical simulations revealed that an obvious decrease in interfacial temperature triggered the solidification and growth of the aluminum layer. Additionally, the specific heat and thermal conductivity of the high-melting-point alloys were found to significantly influence the thickness of the aluminum layer. The hot-dip joining technology is well suited for dissimilar metal bonding involving large contact areas and significant differences in melting points.

Multi-principal-element alloys (MPEAs) exhibit superior strength and good ductility. However, tribological properties of FeCrNi MPEAs remain unknown at nanoscale and complex environments. Here, we investigate the effects of scratching speed, depth, and temperature on microstructural and tribological characteristics of FeCrNi using molecular dynamics simulations combined with an elevated temperature tribological experiment. The scratching force experiences the increase stage, the undulated stage, and the stable stage due to chip formation. Compared to traditional alloy coatings, low force enhances the useful life. With increased speed, the friction coefficient decreases, agreeing with previous work. High speed impacting includes severe local plastic deformation, from dislocation to amorphization. As the scratching depth increases, the average scratch force and friction coefficient increases owing to material accumulation in front of the abrasive particles. The surface morphology and dislocation behavior are significantly different during the scratching process. In addition, we revealed a temperature-dependent friction mechanism. FeCrNi MPEAs have excellent wear resistance at an intermediate temperature, which is attributed to the high Cr content promoting the formation of the compact oxide layer. This work provides atomic-scale mechanistic insights into the tribological behavior of FeCrNi, and would be applied to the design of MPEAs with high performance.

In this paper, the influence mechanism of ultrasound on plastic flow and microstructure features of the aluminum–copper friction stir lap welding (Al/Cu-FSLW) process is systematically investigated by adjusting the welding speed and improving the shear rheology in the plastic stirring zone. Through adjusting the ultrasonic vibration and welding speed, the directional control of mechanical properties is realized. It is found that increasing the welding speed properly is beneficial to enhance the mechanical shear between the tool and the workpiece, thus forming more staggered layered structures at the copper side and improving the tensile strength of the weld. The acoustic softening enhances the viscoplastic fluid mixing and strengthens the mechanical interlock of the Al/Cu lap interface. As the welding speeds increase or ultrasonic vibration is applied, the thickness of Al/Cu intermetallic compound (IMC) decreases, and the tensile strength and elongation of the Al/Cu joints are enhanced. Compared with adjusting the welding speed, the ultrasonic vibration can further refine the copper particles which are stirred into the plastic zone, and the thinning effect of ultrasound on IMC layers is better than that of increasing welding speed. At the welding speed of 60 mm/min, the IMC layer thickness is reduced by 42% under ultrasonic effect. In three welding speed conditions, the UV reduced the absolute value of the effective heat of formation (EHF) for Al₂Cu and Al₄Cu₉ and suppressed the formation of AlCu phase. Meanwhile, only when the welding speed is increased from 60 mm/min to 100 mm/min can the formation of AlCu be suppressed. Under the ultrasonic optimization, the stable improvement of welding efficiency is ensured.

Combining aluminum and steel offers a promising solution for reducing structural weight and fuel consumption across various industries. Pulse in tungsten inert gas (TIG) weld brazing effectively suppresses interfacial brittle intermetallics and enhances joint strength by influencing pool stirring and heat input during aluminum-to-steel joining. However, optimizing the pulsed TIG weld brazing process is challenging due to its numerous welding parameters. This study established statistical models for Al/steel joint strength without reinforcement using response surface methodology (RSM) based on central composite design (CCD). The models’ adequacy and significance were verified through analysis of variance (ANOVA). The four welding parameters influence weld strength in the following descending order: pulse on time > base current > pulse current > pulse frequency. Additionally, interactions between pulse current and pulse frequency, and between pulse on time and base current, were observed. Numerical optimization using RSM determined the optimal pulsed GTA weld brazing parameters for aluminum and stainless steel. With these optimized parameters, the joint strength reached 155.73 MPa, and the intermetallic compound (IMC) thickness was reduced to 3.4 μm.