TC21+TC4-DT线性摩擦焊接头组织与力学性能试验

Microstructure and mechanical properties of linear friction welding joint of TC21/TC4-DT

针对高强TC21和中强TC4-DT异种钛合金进行线性摩擦焊工艺研究,对接头进行不同热处理,接头微观组织和力学性能进行试验分析.结果表明,TC21+TC4-DT线性摩擦焊接头飞边成形良好,飞边表面光滑根部无明显缺陷存在;焊态条件下焊缝组织为典型的魏氏组织结构特征,热处理后焊缝组织析出弥散的针状α相,随着热处理温度的升高析出的针状α相逐渐长大粗化,致使接头冲击和断裂性能先上升后下降;接头拉伸性能与TC4-DT母材相当;700℃/3 h热处理接头、母材高周疲劳性能试验结果表明,接头的疲劳极限达到558 MPa,与TC4-DT基体相当,焊缝组织细化是提高接头疲劳极限的重要原因.

High strength TC21 and medium strength TC4-DT Ti-alloys with dissimilar damage tolerance were linear friction welded(LFW).Different heat treatments were selected for the joints.The microstructure and mechanical properties of the welded joints were studied after heat treatment.The results showed that good flash is formed on both side of the base metal after LFW.The surface of the flash is smooth and no defects are found at the root of the flash.The microstructure of the weld zone(WZ)is widmanstatten in as-welded condition.Precipitated acicularαphase is distributed in the weld zone after heat treatment.With heat treatment temperature increasing the precipitatedαphases are coarsened.The impact properties and fracture toughness properties rises at the first and goes down latter withαcoarsened.Tensile strength of the joints is equal to TC4-DT base metal.The high cycle fatigue limit of the joint is 558MPa at the temperature of 700°C for 3 hours which is equal to TC4-DT base metal.Due to the fine microstructure of WZ the fatigue limit increases.