【目的】设计了一种新型的Ni2CoCr0.5Si0.3Al0.1Ti0.1中熵合金。【方法】在非等原子比Ni-Co-Cr基体的中熵合金中加入微量的Si、Al和Ti元素,并且通过不同温度的时效热处理进一步引入弥散的共格L12相沉淀。【结果】结果表明,700℃时效后的Ni2CoCr0.5Si0.3Al0.1Ti0.1中熵合金具有最优异的力学性能,其屈服强度为783MPa,极限抗拉强度为1252MPa,伸长率为41.6%;相比退火处理样品,经过700℃时效处理使得合金的屈服强度提升了310MPa.分析合金在700℃时效样品的初始微观结构,可以确定合金中不仅存在共格的L12相结构,还有微量的金属间化合物Ni16Ti6Si7相。同时,由于高轧制量的冷轧变形和短时间的退火处理,在初始结构中发现微量的层错、纳米层错网格、Lomer-cottrell锁和位错钉扎现象的存在。其几何必需位错在拉伸过程中呈现出均匀分布,主要的变形模式以滑移为主,且具有层错结构,并没有发现变形孪晶。

【Purposes】 A novel type of Ni2CoCr0.5Si0.3Al0.1Ti  medium entropy alloy is de- signed in this work. 【Methods】 Trace amounts of Si, Al, and Ti elements are added to the non- equiatomic ratio NiCoCr-based medium entropy alloy, and dispersed coherent L12  phase precipita- tion is introduced through aging heat treatment at different temperatures. 【Findings】 The results show that the Ni2CoCr0.5Si0.3Al0.1Ti  medium entropy alloy aged at ℃ has the best mechan- ical properties, with a yield strength of MPa, an ultimate tensile of MPa, and an elon- gation of 41.6%. Compared with the annealed samples, the alloy after aging treatment is in- creased in yield strength by MPa. Further analysis of the initial microstructure of the alloy aged at ℃ reveals the presence of coherent L12  phase structure and trace amount of interme- tallic compound Ni16Ti6Si  phase. Meanwhile, because of the severe deformation through cold rolling and the short time of annealing treatment, trace stacking faults, nano stacking fault net- works, Lomer-Cottrell locks, and dislocation pinning phenomena are found in the initial struc- ture. The geometrically necessary dislocation exhibits a uniform distribution during the stretc- hing process, and the main deformation mode is dominated by dislocation slip with a stacking fault structure.