During the laser additive manufacturing (LAM) process large temperature gradients can lead to high level of residual stress. The residual stress can have irreversible effects such as warping and cracking of parts during and post manufacturing. Heat treatment is an effective method to control and eliminate residual stress. In this paper, the TC4 parts are prepared by laser additive manufacturing, and the influence of heat treatment process on residual stress is researched. Laser ultrasonic technology, as an advanced nondestructive testing method, is applied to measure the residual stress under different heat treatment processes for the first time. The surface wave generated by laser is used to evaluate the residual stress. The results show that laser ultrasonic method can complete the in-situ evaluation of residual stress in additive manufacturing components. The residual stress in TC4 deposited specimen is large, the longitudinal stress is obviously greater than the transverse stress, and the maximum residual stress is about half of the yield strength. The residual stress increases gradually from the upper surface to the bottom layer near the substrate before heat treatment. After heat treatment, the residual stress is reduced to low stress level and a small compressive stress appears. The cooling rate and solution temperature are the main factors affecting the residual stress, and the residual stress increases with the increase of cooling rate and solution temperature. The effect of aging temperature and aging time on residual stress is not obvious. The study serves as useful guidelines for engineers to assessment and regulation of residual stress reasonably in LAM.

在激光增材制造（LAM）过程中，较大的温度梯度会导致高水平的残余应力。残余应力会产生不可逆的影响，例如在制造过程中和制造后零件的翘曲和破裂。热处理是控制和消除残余应力的有效方法。本文通过激光增材制造法制备TC4零件，并研究了热处理工艺对残余应力的影响。激光超声技术作为一种先进的无损检测方法，首次用于测量不同热处理工艺下的残余应力。激光产生的表面波用于评估残余应力。结果表明，激光超声方法可以完成对增材制造组件中残余应力的原位评估。TC4沉积试样中的残余应力很大，纵向应力明显大于横向应力，最大残余应力约为屈服强度的一半。在热处理之前，残余应力从基板附近的上表面到底层逐渐增加。热处理后，残余应力降低到较低的应力水平，并且出现小的压缩应力。冷却速度和固溶温度是影响残余应力的主要因素，残余应力随冷却速度和固溶温度的升高而增加。时效温度和时效时间对残余应力的影响并不明显。