顯微組織與力學(xué)性能的影響
(1. 西北工業(yè)大學(xué) 材料科學(xué)與工程學(xué)院，西安 710072；
2. 北京鋼鐵研究總院，北京 100081)
摘 要: 研究等溫和近等溫鍛造變形溫度對(duì)電子束焊接的異種合金(Ti2AlNb金屬間化合物與TC11兩相鈦合金)焊接界面的顯微組織與接頭拉伸性能的影響。采用OM、SEM對(duì)焊縫區(qū)組織及拉伸度樣斷口進(jìn)行觀察，并對(duì)接頭的拉伸性能進(jìn)行研究。結(jié)果表明：電子束焊接的Ti2AlNb/TC11異種合金焊接界面的顯微組織和接頭的拉伸性能對(duì)變形溫度敏感，在950 ℃變形后，位于焊縫一側(cè)的Ti2AlNb合金中O相的含量大大增加，而位于焊縫另一側(cè)的TC11合金為等軸α相和條狀α相的混合組織，但焊縫上仍可見到斷續(xù)相連的晶界α/α2相；在1 010 ℃變形后，TC11合金具有魏氏體組織特征，這時(shí)焊縫上的晶界α/α2 相完全斷開；經(jīng)950 ℃變形的試樣在室溫拉伸時(shí)，在Ti2AlNb合金中發(fā)生脆性斷裂，這與O相不易協(xié)調(diào)變形有關(guān)，經(jīng)500 ℃高溫拉伸時(shí)，合金表現(xiàn)出較高的強(qiáng)度和較好的塑性，這是由于焊接界面的α/α2相顆粒較小，斷裂位置轉(zhuǎn)移到TC11鈦合金上所致；經(jīng)1 010 ℃變形的試樣表現(xiàn)出一定的強(qiáng)度，但是塑性嚴(yán)重下降，這與TC11鈦合金的魏氏組織特征有關(guān)；因此，異種合金進(jìn)行等溫變形時(shí)，須嚴(yán)格控制變形溫度。
關(guān)鍵字: Ti2AlNb合金；電子束焊接；界面；顯微組織；力學(xué)性能
microstructure and mechanical properties of
electron beam welded joint of dissimilar titanium alloys
（1. College of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072, China;
2. Central Iron and Steel Research Institute, Beijing 100081, China）
Abstract:The effects of deformation temperature on the microstructure of welded interface and mechanical properties of joint by electron beam welded (EBW) dissimilar alloys were investigated. The microstructures of the weld and fractographs of samples were examined by OM and SEM. The results show that the microstructures of the welded interface are sensitive to the deformation temperature. After deformation at 950 ℃, the O phase content increases significantly in the Ti2AlNb alloy at one side of the weld, the microstructure consists of spherical and strip α phase in the TC11 alloy at the other side of the weld, but the grain boundaries α/α2 phase present discontinuously at the weld. After deformation at 1 010 ℃, the microstructure of the TC11 alloy shows Widmanstaten structure, however the grain boundaries α/α2 phases are cut completely. For the samples deformed at 950 ℃, during tensile tests at room-temperature, the brittle fracture takes place at Ti2AlNb alloy, which is related with the inhomogeneous deformation of the O phase. The higher strength and better ductility is because α/α2 phases are fine, the fracture transfers into TC11 titanium alloy in the tensile test at 500 ℃. For the samples deformed at 1 010 ℃, the ductility drop is related with Widmanstaten structure of TC11 alloy. The deformation temperature should be strictly controlled for the isothermal deformation of dissimilar materials joints.
Key words: Ti2AlNb alloy; electron beam welding (EBW); interface; microstructure; mechanical property
