不同成分下铸态AlMoNbTaTiZr高熵合金显微组织的研究

Effects of the Variation of Alloy Composition on Microstructures of As-cast AlMoNbTaTiZr High-entropy Alloys

通过非自耗真空电弧熔炼法制备Al_(a)Mo_(b)Nb_(c)Ta_(d)TiZr(a=1.5,0.5,0.25;b=0.5,0.25,0;c=0.5,0;d=0.5,0.75,1)高熵合金,研究合金元素含量、热力学参数、显微组织间的关系。结果表明,除了Al_(1.5)Mo_(0.5)NbTa_(0.5)TiZr合金由BCC相和富Al-Zr相组成外,其他Al_(a)Mo_(b)Nb_(c)Ta_(d)TiZr合金由单相BCC固溶体相组成。铸态合金呈现典型的枝晶形貌,Al、Zr和Ti偏析于枝晶间,Mo、Ta和Nb偏析于枝晶干,合金成分变化对凝固过程元素分布的影响较小,但Al比Zr对富Al-Zr相析出的影响更为显著。在a,b,c和d数值减小的Al_(a)Mo_(b)Nb_(c)Ta_(d)TiZr中,富Al-Zr相析出被抑制,枝晶组织逐渐粗化。Al_(1.5)Mo_(0.5)NbTa_(0.5)TiZr合金因富Al-Zr相的析出使得显微硬度最高,可达650.0 HV0.3,Al_(0.25)NbTa_(0.5)TiZr合金的最低可达407.6HV0.3。

Al_(a)Mo_(b)Nb_(c)Ta_(d)TiZr (a=1.5,0.5,0.25;b=0.5,0.25,0;c=0.5,0;d=0.5,0.75,1) high-entropy alloys were prepared by a non-consumable vacuum arc melting.The relations of the content of alloying elements,thermodynamic parameters,microstructure evolution were studied.The results show that other AlaMobNbcTadTi Zr alloys are composed of single-phase BCC solid solution phase except Al_(1.5)Mo_(0.5)NbTa_(0.5)Ti Zr alloy composed of BCC phase and Al-Zr rich precipitate.The as-cast AlaMobNbcTadTi Zr high entropy alloy has a typical dendritic microstructure.The elements of Al,Zr and Ti,and the elements of Mo,Ta and Nb are segregated in the interdendritic and dendritic core regions,respectively.The distribution of elements during solidification is scarcely affected by the variation of alloy composition.However,the precipitation of Al-Zr rich precipitate is more significantly affected by Al than Zr.The inhibition of Al-Zr rich precipitate occurs and a solid solution with coarser dendrites is formed in the Al_(a_Mo_(b)Nb_(c)Ta_(d)Ti Zr high-entropy alloys with the reduction of a,b,c and d.Al_(1.5)Mo_(0.5)NbTa_(0.5)Ti Zr alloy shows the highest micorhardness with the value of 650.0HV0.3 due to the precipitation of Al-Zr rich phase,and Al_(0.25)NbTa_(0.5)Ti Zr alloy shows the lowest micorhardness with the value of 407.6HV0.3.