Zr添加对NiAl/Cr(Mo)基共晶合金微观组织和力学性能的影响

EFFECT OF Zr ADDITION ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF NiAl/Cr(Mo)BASE EUTECTIC ALLOY

研究了Zr的添加对含Ti和Hf的NiAl/Cr(Mo)基共晶合金微观组织及压缩性能的影响.结果表明,少量Zr的添加会显著细化合金共晶胞内的NiAl/Cr(Mo)层片,优化共晶胞界区域的NiAl和Cr(Mo)相尺寸;随着Zr含量的增加,共晶胞界的NiAl和Cr(Mo)相明显粗化,且共晶胞界的Heusler相呈半连续状分布;当Zr的含量增加至1%(原子分数)时,共晶胞界的Heusler相形成连续的网状,且有粗大的富Cr相形成.Zr的添加促进了合金中NiAl和Cr(Mo)相中粗大b-NiAl和a-Cr相的析出,且Heusler相形成元素在析出相界面的偏聚导致了大量界面位错的形成.此外,Zr的添加导致了细小Heusler颗粒在NiAl相中的析出.适量Zr的添加可显著提高Ni-33Al-28Cr-5.5Mo-1.0Ti-0.3Hf共晶合金的室温和高温压缩强度,且几乎不降低其压缩塑性,较多Zr的添加会降低合金的压缩塑性.

NiAl base eutectic alloy is an attractive material and promising to use in high temperature environment. However, the inadequate high temperature strength limits its application. In order to improve its strength, Zr was added in the Ti and Hf doped NiAl/Cr（Mo） base eutectic alloys and the effect of Zr addition on microstructure and mechanical properties of the eutectic alloy was investigated in this work. The results show that small addition of Zr can refine the NiAl/Cr（Mo） lamella inside the eutectic cell and optimize NiAl and Cr（Mo） phase morphologyin the intercellular zone. Moreover, the Zr addition promotes the precipitation of bulk Heusler phase along eutectic cell boundary. With the increase of Zr addition, the eutectic cell of the alloys becomes fine, but the NiAl and Cr（Mo）phases in the intercellular zone become coarse and the Heusler phases exhibits semi-continuously distribution along the eutectic cell boundary. When the Zr content increases to 1%（atomic fraction）, the NiAl and Cr（Mo） phases in eutectic cell and intercellular zone are all coarsened obviously. Additionally, coarse Cr- rich phases precipitate in the intercellular zone and Heusler phase forms the continuous network along eutectic cell boundary. The addition of Zr promotes the precipitation of coarse b-NiAl and a-Cr phase in Cr（Mo） phase and NiAl phases, respectively.Moreover, the segregation of Heusler phase forming elements along the precipitate interface leads to the formation of a large number of interfacial dislocations. In addition, the addition of Zr results in the precipitation of fine Heusler particles in NiAl phase. It is shown that appropriate addition of Zr can improve the compression strength of Ni-33Al-28Cr-5.5Mo-1.0Ti-0.3Hf eutectic alloys significantly at room temperature and high temperature without reducing its compression plasticity, but more addition of Zr reduces the compressive plastic of the alloy inevitably.