中文摘要：

采用连续功率超声对AS41镁合金熔体进行孕育处理,研究超声处理功率（强度）、处理时间和处理温度等工艺条件对其凝固组织的影响规律。通过对凝固金相和低倍组织观察以及XRD和Mg2Si相的点阵常数计算,结果表明：连续功率超声孕育处理可以显著细化AS41镁合金的凝固组织,晶粒尺寸仅为无超声处理时的30%～50%;适当提高超声强度和处理温度以及适当延长处理时间均可增强细化效果。优化的处理条件如下：超声强度为30～40W/cm2,处理时间为50～80s,处理温度为650～700℃。此外,超声处理也使Mg2Si相细化和球化,Mg2Si相的点阵常数也发生明显变化。

英文摘要：

Continuous power ultrasound was applied to inoculating the AS41 melt,and the effects of inoculating conditions including ultrasonic power（intensity）,treating time and treating temperature on the solidification microstructures were investigated.According to the metallographical and macroscopical observation together with the XRD pattern and the calculation of Mg2Si phase lattice constant,the results indicate that the continuous power ultrasonic inoculation treatment can refine the grain size of AS41 magnesium alloy markedly,and the grain size with ultrasonic treatment is only 30%？50% as that without ultrasonic treatment.The grain refinement is improved by enhancing ultrasonic intensity,elevating treating temperature（melt temperature）,or prolonging treating time.Its optimum condition is that the ultrasonic field with intensity of 30？40 W/cm2 treats AS41 melt in the temperature range of 650？700 ℃ for 50？80 s.In addition,the ultrasonic treatment also leads to the refinement and spheroidization of Mg2Si and the change of its lattice constant as well.