Mn对铸态Ti-Nb-Mn三元合金显微组织及力学性能的影响

Effect of Mn on Microstructure and Mechanical Properties of As-cast Ti-Nb-Mn Ternary Alloy

采用冷坩埚感应悬浮熔炼方法制备了Ti-16Nb-xMn(x=1,3,5;原子分数,%)合金,通过X射线衍射(XRD)、扫描电镜(SEM)、差热分析(DSC)、透射电镜(TEM)及力学性能测试等方法研究了Mn含量对Ti-16Nb-xMn合金显微组织、相变温度和力学性能的影响。结果表明,Ti-16Nb-5Mn合金具有最高的屈服强度(610 MPa)、抗拉强度(670 MPa)和最好的塑性(27%)。透射电镜分析结果表明,增加Mn含量使合金从正交α″相和体心立方β相两相并存结构转变为β单相结构。合金力学性能的改善一方面由于Mn原子固溶到合金中,提高了合金的屈服强度;另一方面由于Mn作为β稳定元素,提高了合金的β稳定性,抑制α″马氏体的形成,从而提高了合金的塑性。

Ti-16 Nb-xMn（ x = 1,3,5; atom fraction,%） alloys were prepared by cold crucible induction levitation melting. The effect of Mn content on the microstructure,martensitic transformation temperature（ Ms） and mechanical properties of Ti-16 Nb-xMn alloys were studied by XRD,SEM,TEM,DSC and tensile tests. The results showed that the Ti-16 Nb-5 Mn alloy exhibited the highest yield strength of 610 MPa,tensile strength of 670 MPa and elongation of 27%. TEM analysis showed that with the increase of Mn content,the alloy was transformed from a two-phase structure consisting of orthorhombic α″ and body-centered cubic β to a single β phase structure. On one hand,the improvement of yield strength was because,for onething,Mn atom solutionized in the alloy and,for anther,as a β-stabilizing element,Mn improved the β-stability of the alloy,inhibited the formation of α″ martensite and enhanced the plasticity.