焊接电流对Ti2AlNb/TC18焊接界面性能及元素扩散的影响

Effect of welding current on properties and elements diffusion of Ti2AlNb/TC18 welding interface

采用真空电子束焊接对Ti2AlNb和TC18合金进行连接,研究了不同焊接电流时焊接界面的性能及元素扩散情况。结果表明:焊接接头在室温和高温下均获得了较高的抗拉强度。采用同一电流焊接时,TC18侧热影响区的显微硬度值高于该合金基体却低于该侧焊缝区,而Ti2AlNb合金侧热影响区的显微硬度值均高于该侧焊缝区和Ti2AlNb合金基体;在28 mA的焊接电流下,焊接界面的整体显微硬度值均较高,这是因为焊接界面形成了含量较多且尺寸较小的α′马氏体和O相,对界面起到了强化作用。在不同的焊接电流下,合金元素均在焊缝和两侧母材交界处存在较大的浓度梯度,其原因是焊缝金属的快速凝固使得各合金元素没有足够的时间和能量进行充分扩散。

Ti2AlNb and TC18 alloys were welded by vacuum electron beam welding,and the properties and elements diffusion of the welding interface at different welding currents were investigated.The results show that the welded joints have high tensile strength at room temperature and high temperature.When the welding current is the same,the microhardness of heat affected zone at the TC18 alloy side is higher than that of the TC18 alloy matrix,but lower than that of the weld zone at the TC18 alloy side,and the microhardness of heat affected zone at the Ti2AlNb alloy side is higher than that of the weld zone at Ti2AlNb alloy side and the Ti2AlNb alloy matrix.When the welding current is 28 mA,the overall microhardness of the welding interface is high,which is due to the formation of a large amount ofα′martensite and O phase with small size at the welding interface,which plays an important role in strengthening the interface.Under different welding currents,the alloy elements have a large concentration gradient on both sides of the interface of the weld and the base metal,which is due to the fact that the rapid solidification of the weld metal makes the alloy elements not have enough time and energy to diffuse sufficiently.