时效工艺对Cu-Cr-Zr合金带材性能和析出动力学的影响

通过固溶−冷轧−时效工艺制备Cu−1.0Cr−0.1Zr合金带材,研究时效工艺对合金导电率、力学性能和微观结构的影响,并进行析出动力学分析。结果表明,Cu−1.0Cr−0.1Zr合金在430℃时效180 min后获得最佳综合性能,导电率为85.86%IACS,硬度为HV 176.54,抗拉强度为552 MPa。对于在430℃时效的样品,当时效时间从30 min增加到180 min时,细小的fcc-Cr和Cu8Zr3析出相的尺寸从~5 nm长大到~8 nm,且析出相与铜基体的关系由共格转变为半共格。同时,还观察到bcc-Cr相的棒状和球状粗大颗粒(≥300 nm)。此外,建立合金在不同时效温度下的析出动力学方程,绘制等温转变TTT曲线,通过计算获得合金的析出激活能为65 kJ/mol。

高温退火对Cu−0.15Zr合金显微组织和性能的影响

采用快速凝固与热锻相结合的方法,制备组织均匀、晶粒细小的Cu−0.15Zr(质量分数,%)合金,研究高温退火过程中合金显微组织演变、力学性能和电导率。该合金表现出良好的热稳定性,即使在700℃退火2 h后,合金强度仅轻微下降。退火过程中纳米级连续分布的Cu_(5)Zr析出相对位错运动起到钉扎作用,从而使基体强化,同时,尺寸较大的颗粒状Cu_(5)Zr析出相通过钉扎晶界阻碍晶粒长大。在700℃退火2 h后,由于空位、位错、晶界以及基体中溶质Zr原子减少,合金电导率达到峰值88%(IACS)。

超高压下凝固Mg−Zn−Cu−Zr−Ca合金的组织细化与强化机制

在2~6 GPa下对Mg−Zn−Cu−Zr−Ca合金进行凝固。利用SEM和EBSD等分析手段研究高压凝固过程中Ca的分布及对合金凝固组织的影响,并采用压缩试验研究合金的力学性能。结果表明,与常规铸造合金中Ca多偏聚在枝晶间不同,高压凝固合金中Ca多固溶于基体中以及形成Mg_(2)Ca质点相。Mg_(2)Ca质点相为α-Mg晶体强有效的异质晶核,极大增加高压凝固过程总晶核数目并细化凝固组织,6 GPa下合金晶粒尺寸细化至22μm。由于枝晶间无Ca偏聚,更多的Zn固溶到基体中,导致晶间第二相由Zn/Mg比较高的MgZn相(常压)逐渐转变为Zn/Mg比较低的Mg7Zn3相,并且晶间第二相体积分数增加至22%。细晶强化、固溶强化以及弥散强化使6 GPa凝固的Mg−Zn−Cu−Zr−Ca合金强度高达520 MPa。

Damage characteristics of Cu−Cr−Zr alloy rail of electromagnetic railgun after simulated launch

The damage characteristics of different speed sections of Cu−Cr−Zr alloy rail after simulated launch were studied.The microstructure,morphologies and properties of samples were investigated by using XRD,XPS,EBSD,SEM,hardness test,electrochemical test and DSC techniques.It was found that deposition layers were formed on the surfaces of the simulated launch samples.The thickness and surface roughness of these deposition layers increased with increasing the heat effect,suggesting a launch speed dependent damage degree of the arc ablation.The hardness variation of samples is attributed to the effects of the deposition layer and deformation hardening.The surface deposition layer affects corrosion resistance and crystalline characteristics,leading to changes in subsequent service performances.Additionally,the surface texture and plastic deformation ability of the samples are related to the recrystallization degree and deformation grain amount.