采用高温拉伸试验研究TC4钛合金激光焊接接头超塑性变形力学行为,引进变形不均匀系数K表征激光焊板超塑性变形过程中焊接接头与母材的变形不均匀性.结果表明:TC4钛合金激光焊接接头可承受高温超塑变形而不破坏,当初始应变速率低于10~(-2) s~(-1)时流变应力小于60 MPa;接头的变形率及试样的变形不均匀系数随变形温度及应变速率的升高均先升高再降低.在900 ℃、10~(-2) s~(-1)时,接头超塑性变形率和试样的变形不均匀系数K值同时达到最高值46%和0.18,说明焊接接头具有较高的超塑变形能力,应变速率敏感性指数m值大于0.5.
Superplastic deformation mechanical behavior of laser welded joints of TC4 alloys was investigated by hot tensile tests. Non-uniform deformation coefficient K was introduced to characterize the non-uniform deformation between welded joints and base metal during superplastic deformation. Results show that the laser welded joints of TC4 alloys can bear high-temperature superplastic deformation without damage. When the initial strain rate was below 10~(-2) s~(-1), the flow stress was below 60 MPa. Both the deformation rate of joints and K value of specimens were first increased and then decreased with increase of the deformation temperature and strain rate. At 900 ℃and 10~(-2) s~(-1), superplastic deformation rate of joints and K value reach their maximum of 46% and 0.18, respectively at the same time. It reveals that the welded joints have better superplastic deformability, and sensitive index of strain rate m is bigger than 1.5.
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