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采用搅拌摩擦焊(friction stir welding,FSW)实现了2 mm厚TC4钛合金连接,结合数值模拟结果研究了温度分布对焊缝沿厚度方向显微组织特征和接头力学性能的影响规律.结果表明,当焊接速率为50 mm/min且转速为300 r/min时,靠近焊缝表面的材料温度峰值超过b相变温度.随着到焊缝表面距离的增加温度峰值逐渐变小,靠近焊缝底部的材料未超过b相变温度.在温度峰值超过b相变的焊缝区域,显微组织是由初生a相、板条状a相和剩余转变b相组成,且焊缝内部的板条状a相尺寸大于近表面区域.焊缝底部受到动态再结晶作用,呈现尺寸较小的a和b双相组织,且b相在a相基体上分布更均匀.当转速提高到350 r/min时,沿焊缝厚度方向上的超过b相变温度的区域变宽,板条状a相所占面积和尺寸增大,组织中出现板条状a相丛.取向不同的板条状a相散乱分布于组织中,阻碍裂纹扩展,利于接头的抗拉强度.
The effect of temperature distribution on the microstructure characteristics and mechanical properties of the joint along the thickness direction was studied by numerical simulation of friction stir welding (FSW). The results show that, When the welding speed is 50 mm / min and the rotation speed is 300 r / min, the temperature of the material close to the weld surface exceeds the phase transition temperature of b.With the increase of the distance to the weld surface, the temperature peak becomes smaller and closer to the bottom of the weld Of the material does not exceed the phase transition temperature b in the weld peak temperature exceeds the phase transition b, the microstructure consists of a primary phase a lamellar a phase and the remaining transformation b phase, and the weld within the lath The size of phase a is larger than that of the near surface area, and the bottom of the weld is subjected to dynamic recrystallization, showing a-b and b-phase microstructure with more uniform distribution on phase a matrix. When the rotation speed is increased to 350 r / min , The area beyond b-phase transition temperature along the thickness of weld bead widened, the area and size of a-lath a phase increased, and the lamella-a-phase clumps appeared in the microstructure. Distributed in the organization, hinder the crack growth, conducive to joint tensile strength.