磁脉冲辅助半固态钎焊钎缝凝固组织的模拟研究

Simulation of Solidification Microstructure of Brazing Seam in Semi-solid Brazing Assisted by Magnetic Pulse

制备了Zn-15Al半固态钎料,采用磁脉冲辅助半固态钎焊方法对铜铝管进行了钎焊试验;基于LS-DYNA分析了钎焊过程中钎料的剪切流变行为,结合接头微观组织分析,建立了钎料剪切流变速率与初始形核密度的关系。将建立的形核模型耦合到后续冷却过程,采用ProCAST软件模拟分析了磁脉冲辅助半固态钎焊过程中钎缝的凝固行为,分析了钎焊温度和剪切速率对凝固微观组织的影响。结果表明,随钎焊温度升高,晶粒尺寸明显增加;剪切速率增大,形核密度增加,晶粒数量增加,尺寸减小;钎焊温度为410℃时,能够得到良好的钎焊接头组织且钎料晶粒圆整,尺寸细小。

Zn-15 Al semi-solid solder was prepared and brazing experiment of Cu/Al tube was carried out by magnetic pulse assisted semi-solid brazing. The shear rheological behavior of solder during brazing process was analyzed based on LS-DYNA, and the relationship between shear rate and initial nucleation density was established combined with microstructure analysis of the joint. The nucleation model was coupled to the subsequent cooling process, and the solidification behavior of the brazing joint microstructure in the semi-solid brazing process assisted by magnetic pulse was simulated and analyzed by ProCAST software. The effects of the brazing temperature and shear rate on the solidification microstructure were analyzed. The results indicate that the grain size is increased obviously with the increase of brazing temperature. As the shear rate increases, the nucleation density is raised, and the number of grains grows while the grain size is decreased. When the brazing temperature is 410 ℃, desirable microstructure of the brazing joint can be obtained, and the grains become round and smaller.