Mn含量对铸造高铌TiAl合金组织和性能的影响
Effect of Mn content on the microstructure and mechanical properties of cast high Nb containing TiAl alloys
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摘要: 选择两种Mn含量不同的高铌TiAl合金Ti46Al8Nb2Mn0.2B和Ti46Al8Nb1.3Mn0.2B,通过热等静压(HIP)及后续热处理,结合组织和力学性能的分析,研究了Mn含量对高铌TiAl合金的组织和性能的影响.XRD和SEM背散射电子实验结果表明:Mn含量较高的Ti46Al8Nb2Mn0.2B合金,经热等静压及循环热处理,得到的双态组织较粗大,并且有少量脆性β相存在;Mn含量较低的Ti46Al8Nb1.3Mn0.2B合金,经热等静压后直接在双相区长时间保温处理,得到了细小的双态组织,并且完全消除了β相.室温拉伸实验表明,Mn含量的降低提高了Ti46Al8Nb1.3Mn0.2B合金的力学性能,其延伸率、屈服强度和断裂强度分别达到2.4%、548MPa和660MPa.断口形貌分析表明,室温下两种合金都属于解理断裂.Abstract: The microstructure and mechanical properties of two high Nb containing TiAI alloys with different Mn contents, Ti46Al8Nb2Mn0.2B and Ti46Al8Nb1.3Mn0.2B, were studied. XRD and SEM results show that the Ti46Al8Nb2Mn0.2B alloy obtains duplex microstrueture with a few brittle 13 phases after hot isostatic pressing (HIP) and cyclic heat treatment. By thermostatic treatment in two-phase area for long time after HIP, no β phases were found in the microstructure of the Ti46Al8Nb1.3Mn0.2B alloy. Tensile test shows that the mechanical properties improve with decreasing Mn content, and the elongation, yield strength and breaking strength of the Ti46Al8Nb1.3Mn0.2B alloy are 2.4%, 548 MPa and 660 MPa, respectively. The fracture morphologies indicate that the fracture of the two alloys at room temperature belongs to brittle cleavage fracture.
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