(西安建筑科技大學(xué) 冶金工程學(xué)院，西安 710055)
摘 要: 采用真空電子束焊研究不同工藝參數(shù)時Ti2AlNb/TC18異種合金焊接接頭的組織特征和高溫拉伸性能。結(jié)果表明：當(dāng)選用合適的焊接工藝參數(shù)時，TC18側(cè)熱影響區(qū)為細小且均勻分布的針狀α相組織；焊縫的β晶界明顯，在β晶界上分布著晶粒細小的α和α2相；Ti2AlNb側(cè)熱影響區(qū)與焊縫分界面明顯，β晶粒發(fā)生粗化。焊接工藝參數(shù)對 Ti2AlNb/TC18 合金的高溫塑性影響較小，但對其高溫強度的影響較大。當(dāng)焊接速度相同時，焊接電流I=28 mA的高溫拉伸強度最高，為807 MPa；當(dāng)焊接電流相同時，焊接速度 v=6 mm/s的高溫拉伸強度最高，達813 MPa。這是由于焊縫組織相對細小，導(dǎo)致晶界面積的增加，位錯的滑移受阻，因此使其接頭的強度得到提高。當(dāng)采用焊接工藝參數(shù)28 mA、6 mm/s時，試樣的高溫拉伸斷口頸縮明顯、韌窩較大且較均勻，表明采用該組焊接工藝參數(shù)制備的Ti2AlNb/TC18高溫拉伸性能較好，這與其連接界面寬度較窄、組織細小且分布較均勻有關(guān)。
關(guān)鍵字: 真空電子束焊；焊接工藝參數(shù)；Ti2AlNb/TC18合金；焊接界面；高溫拉伸性能；顯微組織
（School of Metallurgical Engineering, Xi’an University of Architecture &Technology, Xi’an 710055, China）
Abstract:The microstructure and elevated temperature tensile properties of Ti2AlNb/TC18 dissimilar alloy welded joints were investigated by vacuum electron beam welding. The results show that, as the welding processing parameters are adopted properly, the fine acicular α phases are distributed homogenously on the HAZ of the TC18 alloy side. β grain boundary of the weld is obvious, and the fine α phase and α2 phase are distributed on the β grain boundary. Moreover, the HAZ on the Ti2AlNb alloy side and the weld are separated obviously, and the β grains are coarsened. Furthermore, the welding processing parameters have little effect on the elevated temperature plasticity of the Ti2AlNb/TC18 alloy, but they have an obvious influence on its elevated temperature strength. When the welding speed is the same, the elevated temperature tensile strength of welding current of 28 mA is the highest (807 MPa). As the welding current is the same, the elevated temperature tensile strength of welding speed of 6 mm/s is the highest (813 MPa). The reason is that the microstructure of the weld is relatively fine, which leads to the increase of the grain boundary area and the obstruction from the dislocation slip. Therefore, the strength of the joint is improved. When the welding parameters are 28 mA and 6 mm/s, the tensile fracture necking is more obvious, and the dimple is larger and more uniform. All of these are demonstrated that the elevated temperature tensile properties of Ti2AlNb/TC18 prepared by the welding parameters are better, which is related to the narrow width of the interface and the fine microstructure as well as its uniform distribution.
Key words: vacuum electron beam welding; welding processing parameters; Ti2AlNb/TC18 alloy; welding interface; elevated temperature tensile properties; microstructure
