Effect of Mn content on the microstructure and mechanical properties of cast high Nb containing TiAl alloys
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摘要: 選擇兩種Mn含量不同的高鈮TiAl合金Ti46Al8Nb2Mn0.2B和Ti46Al8Nb1.3Mn0.2B,通過熱等靜壓(HIP)及后續熱處理,結合組織和力學性能的分析,研究了Mn含量對高鈮TiAl合金的組織和性能的影響.XRD和SEM背散射電子實驗結果表明:Mn含量較高的Ti46Al8Nb2Mn0.2B合金,經熱等靜壓及循環熱處理,得到的雙態組織較粗大,并且有少量脆性β相存在;Mn含量較低的Ti46Al8Nb1.3Mn0.2B合金,經熱等靜壓后直接在雙相區長時間保溫處理,得到了細小的雙態組織,并且完全消除了β相.室溫拉伸實驗表明,Mn含量的降低提高了Ti46Al8Nb1.3Mn0.2B合金的力學性能,其延伸率、屈服強度和斷裂強度分別達到2.4%、548MPa和660MPa.斷口形貌分析表明,室溫下兩種合金都屬于解理斷裂.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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