Al对低中子吸收截面Ti-Zr-Nb高熵合金的微观结构和腐蚀行为的影响

针对Al对低中子吸收截面Ti-Zr-Nb系高熵合金的微观结构和腐蚀行为进行了研究。比较了不含Al和含15at%Al的Ti-Zr-Nb合金的相图、微观结构、氧化行为和腐蚀行为。相图计算结果表明，在熔点下Ti-Zr-Nb三元合金为bcc相，添加的Al会倾向于在合金中形成不同的金属间化合物，而缩小相图中bcc单相区的温度区。XRD和TEM结果表明，熔炼获得的Ti-Zr-Nb三元合金为简单的bcc结构，而Al会导致晶体结构转变为有序的B2结构。通过热重分析和高压釜试验对Ti-Zr-Nb系高熵合金的腐蚀行为进行了研究。结果表明，在腐蚀过程中，Ti-Zr-Nb三元合金的氧化膜容易发生剥落，而添加Al会提高氧化层的稳定性，但不会改变腐蚀氧化层的主要氧化物种类。通过计算反应速率常数和激活能对氧化动力学进行了研究，发现添加Al的Ti-Zr-Nb系合金的高温氧化性能与Zr合金接近。

Effect of Al on Microstructure and Corrosion Behavior of Low Neutron Absorption Cross-Section Ti-Zr-Nb High Entropy Alloys

The effect of Al on the microstructure and corrosion behavior of low neutron absorption cross-section Ti-Zr-Nb high entropy alloys was investigated. The phase diagram, microstructure, oxidation behavior and corrosion behavior of Ti-Zr-Nb alloys without Al addition and with ~15at% Al were compared. The phase diagram shows that below the melting temperature, Ti-Zr-Nb ternary alloys are bcc phase, and Al is inclined to form intermetallics in Ti-Zr-Nb alloys, and thus reduces the single-phase bcc temperature region in phase diagram. XRD and TEM results show that as-cast Ti-Zr-Nb ternary alloys is simple bcc structure, and Al will transform the crystal structure to ordered B2 structure. The corrosion behavior of Ti-Zr-Nb alloys was studied by thermogravimetric analysis and autoclave exposure. Results show that corrosion oxide layer formed on TiZrNb ternary alloys tends to spall during corrosion process, while Al addition will increase the stability of oxide layer without changing the main type of oxide formed during corrosion process. Oxidation kinetics was evaluated by calculating reaction rate constants and activation energies, and it is found that the high temperature oxidation property of Ti-Zr-Nb alloys with Al addition is comparable to that of Zr alloys.