CAJ | 학술논문

针对7050铝合金表面激光熔覆Al/Ti复合粉体，建立了三维瞬态温度场有限元模型，模拟了不同离焦量条件下的熔池大小、温度梯度、冷却速度及形状控制因子。结果表明，熔池宽度与深度尺寸随着离焦量数值的增大先增大后减小，在离焦量为20 mm时熔池宽度与深度都出现了最大值。沿熔池深度方向(即Z向)的温度梯度数值最大，散热条件最好，表明熔覆凝固过程中的晶粒生长方向主要集中在Z向。离焦量为40 mm时的冷却速度最大、晶粒细小，离焦量为80 mm时的冷却速度最小、晶粒粗大，且得到实验验证。离焦量为60 mm时的形状控制因子最大，金相组织出现柱状晶；离焦量为80 mm时的形状控制因子最小，金相组织主要为胞状晶，并有相应的实验验证。
침대7050려합금표면격광용복Al/Ti복합분체，건립료삼유순태온도장유한원모형，모의료불동리초량조건하적용지대소、온도제도、냉각속도급형상공제인자。결과표명，용지관도여심도척촌수착리초량수치적증대선증대후감소，재리초량위20 mm시용지관도여심도도출현료최대치。연용지심도방향(즉Z향)적온도제도수치최대，산열조건최호，표명용복응고과정중적정립생장방향주요집중재Z향。리초량위40 mm시적냉각속도최대、정립세소，리초량위80 mm시적냉각속도최소、정립조대，차득도실험험증。리초량위60 mm시적형상공제인자최대，금상조직출현주상정；리초량위80 mm시적형상공제인자최소，금상조직주요위포상정，병유상응적실험험증。
To study the process of laser clad Al/Ti composite powder above 7050 aluminum, a three dimensional model was established, which can simulate the molten pool size, the temperature gradient, cooling rate and the shape control factor in the condition of different defocusing amount. The simulated results show that the width and depth of the molten pools are positively correlated to the defocusing amount, but negatively correlated after the defocusing amount reaches 20 mm. Both the max temperature gradient numerical value and the best cooling condition appear in the Z direction, which also indicate the growth direction of grains mainly concentrates on the Z direction. The cooling speed reaches the highest and the grain size is small when the defocusing amount is 40 mm. The cooling speed is lowest and grain size is big when the defocusing amount is 80 mm. Moreover, the shape control factor is biggest and the crystal microstructure is columnar when the defocusing amount is 60 mm, and the shape control factor is smallest with cellular crystal microstructure when the defocusing amount 80 mm. Finally, the simulated results about both the grain size and the crystal microstructure of the molten pool are verified by the experiment study.