TC4钛合金搅拌摩擦焊厚度方向的显微组织

发布时间：2018-06-03 23:07

本文选题：搅拌摩擦焊 + TC钛合金　；参考：《金属学报》2015年11期

【摘要】：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.
[Abstract]:Friction stir welding (FSW) was used to realize the connection of 2 mm thick TC4 titanium alloy. The effect of temperature distribution on the microstructure and mechanical properties of the joint along the thickness direction was studied by numerical simulation. The results show that when the welding rate is 50 mm/min and the rotational speed is 300 r/min, the peak temperature of the material near the weld surface exceeds the b phase transition temperature. With the increase of the distance from the weld surface to the weld surface, the peak value of the temperature becomes smaller, and the material near the bottom of the weld seam does not exceed the b phase transition temperature. In the weld zone where the temperature peak value exceeds b, the microstructure is composed of primary a phase, plate stripe a phase and residual transition b phase, and the size of the strip a phase inside the weld is larger than that of the near surface region. The bottom of the weld is subjected to dynamic recrystallization, showing smaller size of a and b dual phase structure, and the distribution of b phase on a phase matrix is more uniform. When the rotational speed is increased to 350 r/min, the area beyond b phase transition temperature along the weld thickness direction becomes wider, the area and size of a phase in the plate increase, and the lamellar a phase cluster appears in the microstructure. The stripe a phase with different orientation distributes in the microstructure, which hinders the crack propagation and is beneficial to the tensile strength of the joint.
【作者单位】：沈阳航空航天大学航空航天工程学部;北京航空制造工程研究所;
【基金】：国家自然科学基金项目51204111 辽宁省自然科学基金项目2013024004和2014024008资助~~
【分类号】：TG453.9;TG407

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