Al含量对Al_xCoCrFeNi系高熵合金组织和耐蚀性能的影响

Effect of Al content on microstructure and corrosion resistance of Al_xCoCrFeNi high entropy alloys

通过真空电弧熔炼方法制备Al_xCoCrFeNi系高熵合金(HEAs,x=0.5,1.0,1.5,2.0),分析了不同Al含量对合金物相组成和显微组织的影响,同时研究了合金在模拟海水中的耐蚀性能。结果表明:Al_xCoCrFeNi系高熵合金均由简单的FCC或BCC相组成,无脆性金属间化合物相生成;当x=0.5时,合金主要为FCC相;随着Al含量的增加,合金相结构由FCC相向BCC相转变,显微组织由树枝晶向等轴晶转变,并且逐渐细化;Al_xCoCrFeNi系高熵合金的腐蚀是典型的点蚀机制,随Al含量的增加,HEAs在3.5%NaCl溶液中的耐蚀性变差,主要是由于合金中富Ni、Al的有序BCC相的析出与其余相形成了大量的微观腐蚀电池,使得有序BCC相严重侵蚀。因此,降低Al含量有利于提高Al_xCoCrFeNi系高熵合金的耐蚀性。

AlxCoCrFeNi high entropy alloys (HEAs,x =0.5,1.0,1.5,2.0)were prepared by vacuum arc melting,and the effect of different Al content on phase composition and microstructure of the alloys was analyzed,the corrosion resistance of the alloys in simulated seawater was also studied.The results show that the AlxCoCrFeNi high entropy alloys are composed of simple FCC or BCC phases without brittle intermetallic compound phase,and when x =0.5,the main phase is FCC phase.With the increase of Al content,the phase structure of the alloys changes from FCC phase to BCC phase,and the microstructure changes from dendrite to equiaxed crystal,and gradually refines.The corrosion of the AlxCoCrFeNi high entropy alloys is a typical pitting mechanism.With the increase of Al content, the corrosion resistance of the AlxCoCrFeNi high entropy alloys in 3.5%NaCl solution becomes worse,mainly due to the precipitation of the ordered BCC phase rich in Ni,Al in the alloy and the formation of a large number of micro-corrosion cells with the remaining phases, which results in the serious erosion of the ordered BCC phase.Therefore,reducing the content of Al can improve the corrosion resistance of the AlxCoCrFeNi high entropy alloys.