热力因素对合金元素在Ti-24Al-15Nb-1.5Mo/TC4焊接界面上扩散规律的影响

Effect of Hot and Force Factors on the Microhardness and Elements Diffusion at Ti_3Al/TC 4 Seam

研究了2种状态的金属问化合物基合金Ti-24Al-15Nb-1.5Mo与TC4钛合金毛坯经真空电子束焊接后,锻造温度、热处理制度、变形量等热力因素以及它们的交互作用对合金元素Al,Nb,V在焊接界面上扩散规律的影响。研究发现:增加变形和提高热处理温度,可以增大原子迁移的动能,有利于提高合金元素的扩散速度,均匀焊缝显微硬度;加大变形量,有利于提高晶格畸变能并细化晶粒、改变相的形态、减小相的尺寸,缩短合金元素的扩散路程。Nb在重新凝固区Ti-24Al-15Nb-1.5Mo一侧浓度高于合金的名义成分是由于在焊缝区α2→α变化时,Nb从DO19结构点阵中扩散出来,填补Al,Mo扩散后的空位,造成局部堆积所致。变形后热处理规范的不同,导致焊缝区的显微硬度不同,这与热处理过程中显微组织变化有关。

The influence of heat and force factors and their interaction, such as forging temperature, heat treatment process, deformation amount, on the element diffusion of Al, Nb, V at weld zone has been investigated for the Ti-24Al-15Nb-1.5Mo/TC4 dual alloy billet after welded in vacuum and rolled or treated. Investigations showed that the energy of atom motion can increase with the increase of deformation amount and heat treatment temperature, favorable for the elements diffusion and the homogenization of micro-hardness due to the change of shape and size for the grains and phases and short diffusion journey of fine grains at the weld seam. It is found that the concentration of niobium is high at the Ti-24Al-15Nb-1.5Mo side of weld seam. There are two reasons: one is niobium diffusion out from DO19 lattice when re-solidified during welding; the other is local deposit of niobium to fill up the vacancies when Al, Mo diffused out the lattice. The heat treatment route can affect the diffusion rate through changing the morphology of microstructure at weld zone.