模拟研究离焦量对7050铝合金Al/Ti熔覆过程的影响  

Influence of defocusing amount on the process of Al/Ti cladding above 7050 aluminum alloy based on numerical simulation study

作　　者：李建忠[1] 黎向锋[1] 左敦稳[1] 许瑞华[1] 陈竹[1] 

机构地区：[1]南京航空航天大学机电学院,江苏南京210016

出　　处：《红外与激光工程》2015年第4期1126-1133,共8页Infrared and Laser Engineering

基　　金：航空科学基金(2010ZE52056);江苏省精密与微细制造技术重点实验室基金;南京航空航天大学研究生创新基地(实验室)开放基金(kfjj201467);江苏省研究生培养创新工程(SJLX_0120)

摘　　要：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。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.

关 键 词：激光熔覆 离焦量 Al/Ti复合粉体 温度梯度 冷却速度 

分 类 号：TB34[一般工业技术—材料科学与工程]