Mn含量对Ti-6Al-4Mo合金显微组织和力学性能的影响

Effect of Mn on the microstructure and mechanical propertiesof Ti-6Al-4Mo alloy

摘要:

钛合金因其优异的综合性能在各个工程领域都有很大的应用潜力,但较低的弹性模量限制了其在高强度、高刚性材料结构件中的应用。本文以开发综合力学性能良好的高弹性模量钛合金为研究目的,采用冷坩埚悬浮熔炼法制备了Ti-6Al-4Mo-xMn(x=0,1,2,3,4 wt%)合金,研究了Mn含量对合金显微组织和力学性能的影响。结果表明,Ti-6Al-4Mo-xMn合金由α和β相组成,未出现Ti-Mn相。随着Mn含量的增加,合金的α→β相变温度降低,合金中β相的体积分数增加,合金的组织变细,魏氏组织逐渐增多；合金的硬度从30 HRC增加到46 HRC,抗拉强度从838 MPa增加到1266 MPa,这是因为Mn元素在合金中引起了固溶强化和组织细化；合金的弹性模量呈现先升高后降低的趋势,当Mn含量为1 %时,合金的弹性模量最高,约136 GPa,同时抗拉强度为916 MPa,较Ti-6Al-4V合金分别提高24.0 %和3 %,综合力学性能最好。

Abstract:

Titanium alloys exhibit great potential for applications in various engineering fields due to their excellent comprehensive properties, whereas the lower elastic modulus significantly limits their usage in structural parts that require for high strength and high rigidity of materials. In order to develop high elastic modulus titanium alloy with good comprehensive mechanical properties, Ti-6Al-4Mo-xMn (x=0, 1, 2, 3, 4 wt.%) alloys were prepared by a cold crucible suspension melting method. The effect of Mn content on the microstructure and mechanical properties of the alloy was systematically investigated. The results demonstrated that the prepared Ti-6Al-4Mo-xMn alloys were composed of α and β phases without Ti-Mn phase impurity. With the increase of Mn content, the α→β phase transition temperature decreased, resulting in an increase in volume fraction of β phase. Moreover, the microstructure of the alloys gradually became finer and evolved toward Widmannstatten microstructure. The hardness of the alloy increasesd from 30 HRC to 46 HRC; and the tensile strength increased from 838 MPa to 1266 MPa, which is because solution strengthening and microstructure refinement caused by Mn atoms. With the increase of Mn content, the elastic modulus of the alloy increased first and then decreased. When the Mn content is 1%, the elastic modulus of the alloy exhibited a highest, value of 136 GPa, and the tensile strength was 916 MPa, which are 24.0% and 3% higher than those of Ti-6Al-4V alloy, respectively.