中文摘要：

对纯镍同轴送粉激光熔覆过程中宏观温度场与熔池底部微观组织生长进行了二维耦合模拟计算。首先利用标志变量法计算因粉末的加入而产生的边界动态改变，进行宏观温度场模拟，再取熔池底部一宏观单元进行网格细化，作为微观模拟区域，并通过插值计算获得微观模拟区域的初始温度条件，同时在计算中用宏观单元温度实时修正微观计算区域温度边界条件。在微观区域底部设置晶核，确定相场初始条件，并采用相场法进行微观区域的相场、温度场耦合计算，获得微观组织形貌。最后进行试验，在镍板基底上熔覆镍粉，模拟所得微观组织形貌与试验所得基本吻合，验证了模拟结果的正确性。

英文摘要：

Two-dimensional macroscopic temperature field of the work-piece and evolution of the microstructure which is located at the bottom of the melt pool in coaxial laser cladding are calculated. Formation of the clad bead due to powder feeding is simulated. Macroscopic temperature field is computed. Then, one macroscopic cell at the bottom of the melt pool is re-meshed for calculation of the microstructure evolution. Initial temperature conditions are calculated with interpolation method among the temperatures of its nearest neighbor macroscopic cells. Its four boundary temperatures can be considered as the same as its four neighbors＇ temperatures. Crystal nucleus is set in the lower boundary of microscopic domain. Finally, phase field and temperature field are calculated using phase-field method. The calculation results agree with the experimental results, which proves the validity of the macro and micro coupling model.