Refractory high-entropy alloys (RHEAs) have emerged as a leading frontier in advanced alloy research due to their promising mechanical properties at both ambient and elevated temperatures. However, their widespread application is hindered by inherent limitations, including high density and the strength-ductility trade-off. In this work, a novel (Ti45Nb30Cr15V10)(96)Al-4 lightweight RHEA was designed and processed through grain refinement combined with the introduction of a small amount of C15 Laves precipitates. The as-cast alloy with a single body-centered cubic (BCC) phase shows a tensile yield strength of similar to 1018 MPa and a fracture strain of similar to 8.9%. After cold-rolling and subsequent annealing, the alloy develops a refined BCC matrix containing dispersed C15 Laves precipitates achieving an enhanced strength-ductility synergy with a tensile yield strength of similar to 1092 MPa and a fracture strain of similar to 14.1%. The underlying mechanism is primarily attributed to strong solid-solution strengthening and complex deformation behaviors, including multi-directional planar slip, cross-slip, and dislocation intersections, which are facilitated by grain refinement and the presence of C15 Laves precipitates.

目的 基于全量流动理论,研究管材弯曲成形过程中的外侧破裂和内侧起皱,分析其产生的原因及控制方法.方法 采用理论解析方法,建立了管材弯曲变形应力、应变计算公式,推导管材外侧破裂和内侧起皱发生的判据,并试验验证了预测公式的可靠性.结果 基于推导的应力、应变计算公式,依据临界许用变形程度,建立了管材外侧破裂判据;采用能量准则,提出了管材弯曲过程起皱发生公式,确定了起皱失稳计算公式的各个边界参数.结论 试验与理论结果表明,构建的最小壁厚下许用R/r(弯曲半径与管材平均半径的比值)计算公式、基于起皱失稳计算的许用R/r(弯曲半径与管材平均半径的比值)计算公式均有较高精度,可用于指导弯管工艺参数设计与优化.

The bulk Cu billets with ultrafine-grained microstructure were successfully processed from full-annealed coarse grained oxygen-free high conductivity (OFHC) Cu by the cyclic extrusion and closed compression (CECC), subsequently annealed at different temperatures. The evolution of the microstructure and mechanical properties was systematically studied. The results show that the effective strain per CECC process is ε=2.77, with further annealing treatment, a high-efficiency grain refinement is realized. After two cycles of CECC process and annealing at 350 °C for 1 h, the grain size refined to ～3 μm, the tensile strength increased to 280 MPa with a high ductility of 54%. Furthermore, a homogeneous structure and mechanical properties in the bulk copper billets for post-forging could be obtained.

针对Mg-10Gd-3Y-Zr高强韧镁合金,采用相图热力学计算方法(CALPHAD)、相平衡热力学计算软件(PANDAT),根据扎克哈罗夫经验公式等初步确定合金的固溶、时效温度范围,研究了合金时效硬化曲线、时效温度及时间对合金力学性能及显微组织的影响.结果表明:Mg-10Gd-3Y-0.6Zr镁合金的最佳热处理工艺为225℃×20 h直接时效,此时组织中强化相析出完毕,且均匀分布,对应的抗拉强度为490 MPa,断后伸长率为11％,拉伸断裂为韧性断裂.

Lubrication of warm forming moulds is of great significance for improving the product quality, reducing the deformation force, and prolonging the service life of moulds. In this paper, the film-forming property, anti-friction stick resistance, corrosion resistance and clean ability of several types of liquid lubricant were studied, a new type of flameless water-based graphite lubricant was prepared, and its high-temperature lubricating performance was researched. The test results show that the lubricant has better lubricating property, and is easy to use and free of pollution as a new type of water-based lubricant.

在应变速率为0.005~1 s-1、温度200~275℃条件下,利用Instron-5500热模拟机,对经过等通道角挤压(Equal Channel Angular Extrusion,ECAE)后的AZ91D镁合金的高温压缩特性进行了研究,得到了ECAE-ed态AZ91D镁合金真实应力-应变曲线,分析了挤压温度、应变速率等对其的影响,得出本构方程的一系列常量,建立了ECAE-ed态AZ91D镁合金在高温压缩中的本构方程关系式,并与铸态AZ91D镁合金进行了对比.结果表明:热压缩过程中,ECAE-ed态AZ91D镁合金与铸态一样,流动应力随温度的升高而降低,随应变速率的升高而升高;流动应力也可以用双曲正弦函数来描述,且双曲正弦值随Zener-Hollomon参数的自然对数的升高呈线性升高;两者同为正应变速率敏感材料,但ECAE-ed态AZ91D镁合金要比铸态应变速率敏感性小,其指数从铸态的m=0.14下降为0.096,变形激活能从182.65 kJ/mol上升为227.14 kJ/mol.研究结果对AZ91D镁合金进一步塑性成形和应用具有指导意义.

目的 优化低镁含量ZL305铝合金热处理工艺参数.方法 采用正交试验法,研究固溶温度、固溶时间、淬火介质对低镁ZL305铝合金力学性能和组织的影响.结果 固溶温度对抗拉强度的影响最大且显著,固溶时间和淬火介质温度对抗拉强度的影响次之,但不显著;对断后伸长率影响最大的是固溶温度,其次是淬火介质温度和固溶时间,但影响均不显著.结论当采用固溶温度为495℃、固溶时间为12 h、淬火介质温度为25℃的处理参数时,低镁ZL305铝合金材料的固溶效果最优.