合金化元素Ti对Laves相Cr_2Nb力学性能及耐蚀性的影响

采用真空非自耗电弧熔炼工艺制备了Cr2Nb-XTi(X=5,10,15,at%)合金,利用光学显微镜(OM),X射线衍射(XRD)仪,扫描电镜(SEM)对电弧熔炼态铸锭的组织进行了研究,探讨了合金化元素Ti的含量对Laves相Cr2Nb力学性能及耐蚀性的影响。结果表明:3种成分的电弧熔炼态合金凝固组织主要由C15-Cr2(Nb,Ti)相和六方的β-(Ti,Nb)以及体心立方结构的β-(Nb,Ti)相组成。在5Ti和10Ti合金冷速较小的铸锭上部凝固组织中出现了亚稳相C14-Cr2(Nb,Ti)。通过对合金力学性能研究表明,随合金化元素Ti含量的增加,Laves相Cr2Nb合金的显微硬度逐渐降低,断裂韧性增大,当Ti含量达到15at%时,合金的断裂韧性达到了3.1 MPa·m1/2,比单相Laves相Cr2Nb提高1倍。另外,对腐蚀性能的测试表明,Ti含量增加材料腐蚀性能下降,但15Ti合金仍表现出良好的耐蚀性。

Effects of Ti Addition on the Mechanical Properties and Corrosion Resistance of the Cr2Nb Laves Phase

The ternary alloys of Cr2Nb-XTi (X=5, 10, 15, at%) were prepared by vacuum non-consumable arc melting. The solidification microstructures of arc-melted alloy were investigated using optical microscope (OM), X-ray diffraction (XRD) as well as scanning electron microscope (SEM), and the effects of Ti addition on the mechanical properties and corrosion resistance of Laves- phase Cr2Nb were also studied. The results show that the solidified microstructures of these ternary alloys are mainly composed of C15-Cr2(Nb,Ti), a-(Ti,Nb) and b-(Nb,Ti). A metastable phase C14-Cr2(Nb,Ti) is observed only in the top part of the arc-melted ingots of Cr2Nb-5Ti and Cr2Nb-10Ti alloys at low cooling rate. Meanwhile, with the increase in Ti content, the microhardness of Cr2Nb-XTi alloy decreases gradually and the alloy fracture toughness increases continuously. As the Ti content reaches 15at%, the fracture toughness of the alloy Cr2Nb-15Ti could attain 3.1 MPa.m1/2, twice of that of the single-phase Cr2Nb. In addition, as the Ti content increases, the corrosion performance of the alloy Cr2Nb-XTi declines, but the alloy Cr2Nb-15Ti still exhibits well corrosion resistance.