(哈尔滨工业大学 现代焊接生产技术国家重点实验室，哈尔滨 150001)
摘 要: 采用透射电子显微镜，研究显微组织为等轴状结构的细晶粒Ti-6Al-4V合金在3种焊接参数作用下焊接接头粗晶区的精细结构，并测量接头显微硬度的分布。结果表明：粗晶区晶内初生α′马氏体随热输入增大显著粗化，其形态特征由针状长大成为板条状；在较大热输入下相互平行排列的α′马氏体板条束引起粗晶区强度和延展性下降；初生α′马氏体内部的亚结构以位错和堆垛层错为主，并存在少量孪晶，随热输入增大，位错密度增加；热输入增大也引起由残余β相转变生成的次生α′尺寸增大；3种焊接参数下的热影响区中均未出现软化现象。
关键词：细晶粒钛合金；粗晶区；精细结构；马氏体相变；亚结构
关键字: 细晶粒钛合金；粗晶区；精细结构；马氏体相变；亚结构
（National Laboratory of Advanced Welding Production Technology, Harbin Institute of Technology,
Harbin 150001, China）
Abstract: Compared with conventional Ti-6Al-4V alloy, the fine grained Ti-6Al-4V has higher mechanical properties and better machinability, whereas microstructure transformation of this alloy results in reduced properties of the welded joints under welding thermal cycle. The fine structure in coarse grain region was studied by TEM and the microhardness along the welding seam was measured under three welding parameters during welding of fine grained Ti-6Al-4V with equiaxed crystal. The results show that the primary α′ martensite is greatly coarsened and the fine acicular martensite evolves into α′ plates with increasing heat input. When the heat input is higher, the coarse colony α′ composed of parallel arrangement martensite plates decreases the strength and ductility in coarse grain region. Furthermore, the substructure in martensite plates contains predominately dislocations and staking faults with a few platelets containing twins. Continued increments in heat input increase the dislocation density of α′ phase, as well as the retained β phase. A great quantity of β phase is retained when cooling to low temperature. This less-stabilized retained β phase tends to undergo transformation to coarsener second α′ phase with increasing heat input during subsequent cooling. No softened zone exists in the heat-affected zone with different welding heat inputs.
Key words: fine grained titanium alloy; coarse grain region; fine structure; martensitic phase transformation; substructure
