AlCoCrFeNiBx 高熵合金微结构与性能

本文系统研究了 B 元素对高熵AlCoCrFeNiBx (x denotes the atomic fraction of B element 0, 0.1, 0.25, 0.5, 0.75 and 1.0)合金的微结构和性能的影响。其中添加的B元素含量为0.1时AlCoCrFeNi 高熵合金的形貌从等轴晶转变为枝晶形貌。 其中在等轴晶的内部可以观测到调幅分解结构。当 x>0.1时, 枝晶和调幅分解结构都逐渐消失了，但是越来越多的硼化物开始出现了。这个转变归因于 Cr-B 和Co-B之间高的负混合焓.随着B元素的增加， AlCoCrFeNiBx高熵合金的结构从B2 BCC 结构向B2 BCC FCC 结构的转变, 最后形成了 B2 BCC FCC 以及硼化物的混合结构。 随着B元素的添加硬度值从 HV486.0 下降到了 HV460.7， 然后增加到 HV615.7，其中x=0.1时合金的硬度最低。合金的压缩强度随B元素的增加明显下降，当x=0.25时，合金具有最大的压缩强度，但是当x =0.75时， 由于硼化物的大量生成合金在弹性变形阶段就发生了断裂。随着B含量增多合金的矫顽力和饱和磁化强度开始下降. 下降的矫顽力显示合金具有很好的软磁性能。

Microstructure and properties of AlCoCrFeNiBx high entropy alloys

The influences of B element on the microstructure and property of AlCoCrFeNiBx high entropy alloys (x denotes the atomic fraction of B element 0, 0.1, 0.25, 0.5, 0.75 and 1.0) were investigated. The AlCoCrFeNi high entropy alloy exhibit equiaxed grain morphology, then turns to dendrite structure when B content, x=0.1. The spinodal decomposition microstructure can be clearly observed in equiaxed grains. When x>0.1, both of the dendrite and the spinodal decomposition microstructure gradually disappeared, but much borides formed instead. The transformation is attributed to the high negative mixing enthalpy of Cr-B and Co-B. The microstructures of AlCoCrFeNiBx high entropy alloys changed from B2 BCC structures to B2 BCC FCC structures, finally formed B2 BCC FCC and borides mixing structures with the increased B elements. And the hardness declined from HV486.0 to HV460.7, then rose to HV615.7 as the addition of B element. The lowest hardness value is obtained when x=0.1. The compressive fracture strength shows a distinct decrease with B addition. The maximum compression strength is 2227MPa when x=0.25. But when x reached 0.75, the samples fractured during the elastic deformation due to the formation of hard and brittle borides. The coercive forces and the specific saturation magnetizations of the alloys decrease as the contents B element increase. The decreasing coercive forces show a better soft magnetic behavior.