形变+退火对内燃机用FeCoCrNiB_x高熵合金组织演变的影响

Influence of deformation and annealing on microstructure evolution for FeCoCrNiB_(x) high entropy alloy used in internal combustion engine

为了提高非等原子比高熵合金(Fe50Ni30Co10Cr10)的力学性能,在该合金中加入B元素作为间隙增强原子,对其进行变形处理与退火后,实现了对该合金显微组织的精确调控,并分析了经过不同时间与温度退火处理后该合金发生的再结晶转变过程。研究结果表明:FeCoCrNi高熵合金在添加B元素后会引起σ相温度发生小幅下降,随着温度逐渐下降,在574℃时生成了Cr_(5)B_(3)相。铸态试样内含有fcc基体相与Cr_(5)B_(3)第二相两种物相结构。在变形量较小状态下,晶粒外形主要以树枝晶形态为主,晶内组织发生了滑移,形成了明显的台阶外形;变形量达到50%后,晶粒明显拉长,形成了扭折带变形组织,树枝晶结构已逐步转变为扁平状组织;随着变形量增加,晶粒尺寸逐渐减小,晶粒明显细化。当退火时间达到30 min时,形成的晶粒尺寸与退火时间为10 min的晶粒尺寸存在明显差异,并未出现晶粒长大的情况,等轴晶内也同样形成了大量的hcp板条组织。

In order to improve the mechanical properties of high entropy alloy(Fe50Ni30Co10Cr10)with non-equal atomic ratio,B ele-ment was added to the alloy as a clearance enhancement atom.After the deformation treatment and annealing,the precise control of the al-loy microstructure was realized,and the recrystallization transformation processes of the alloy after annealing at different times and temper-atures were analyzed.The results show that the addition of B element to FeCoCrNi high entropy alloy causes a small drop in the tempera-ture ofσphase,and with the gradual decreasing of the temperature,Cr_(5) B_(3) phase is formed at 574℃.Furthermore,the as-cast sample contains two phase structures with the fcc matrix phase and the Cr 5 B 3 second phase.In the state of small deformation,the grain shape is mainly dendritic,and the intragranular structure slips to form the obvious step shape.After the deformation reaches 50%,the grains are obvious elongated to form the deformation structure of the twisted band,and the dendritic structure gradually changes into a flat structure.With the increasing of deformation amount,the grain size gradually decreases,and the grains are obviously refined.When the annealing time reaches 30 min,the grain size formed is significantly different from the grain size annealed at the annealing time of 10 min without the condition of grain growth,and a large number of hcp lath structures are also formed in the equiaxed grains.