TC4钛合金CO2激光深熔焊接头非线性损伤研究

Study on Nonlinear Damage Evolution of CO2 Laser Deep Penetration Welded Joint for TC4 Titanium Alloy

摘要:

针对TC4钛合金CO2激光深熔焊接接头具有组织性能非线性大梯度特征，并对其塑性损伤行为产生影响的科学问题，采用多试样拉伸试验法研究其非线性塑性损伤行为，提出采用金相法检测的微孔洞体积分数以表征塑性损伤程度。结果表明：TC4钛合金激光深熔焊接头的塑性损伤过程表现为微孔洞的产生与聚合；微孔洞体积分数沿焊接接头从焊缝、热影响区(HAZ)至母材呈非线性分布；激光焊接接头的焊缝、HAZ和母材的微孔洞长大规律和施加应力与显微组织有关，在应力较小时，粗大的晶粒尺寸使得焊缝损伤大于HAZ损伤，而在应力较大时，晶内微孔洞使得HAZ损伤大于焊缝；而且随着施加应力的增大，HAZ中的微孔洞体积分数增长速度比焊缝快

Abstract:

In order to understand the effects of nonlinear microstructures on the damage evolution in laser welded joint of titanium alloy, a multi-specimen method with volume fraction of microvoids was applied to estimate the damage evolution for TC4 titanium alloy. The results show that there are great nonlinear gradient distributions of the microstructure morphology in TC4 laser deep penetration welded joints from weld metal, HAZ to base metal, the damage performance and mechanism change according to these gradient characters, the damage mechanism presents the pattern of microvoids-polymerization, and the volume fraction of microvoids has a great gradient distribution which increases faster in the base metal near welding HAZ than in the weld metal as the load increasing.