Effects of shot speed and biscuit thickness on externaly solidified crystals of high-pressure diet cast AM60B magnesium alloy

Standard mechanical test bars with a diameter of 6.4 mm and a gauge length of 50 mm were processed, and the microstructures of die cast AM60B alloy under different die casting process parameters were observed. The influences of the slow shot speed, the fast shot speed and the biscuit thickness on the externally solidified crystals （ESCs） were investigated. With the increase of the biscuit thickness, the number of the ESCs in the cast samples decreases. Under a low slow shot speed, larg ESCs are found in the cast structure and a high fast shot speed results in more spherical ESCs. The relationships between ESCs and process parameters were also discussed.

压铸AM60B镁合金TIG焊组织研究

对压铸AM60B镁合金板钨极氩弧焊缝显微组织进行了观察分析。结果表明,焊缝中心区由细小均匀的等轴晶和呈网状分布于晶界的高相比例Mg17Al12共晶相组成,在接近上自由表面分布着细小圆形气孔;靠焊缝侧的熔合区集中出现不同尺寸的气孔和微观疏松,显微组织由粗大等轴晶和数量明显减少、呈蠕虫状和颗粒状分布在晶界的Mg17Al12共晶相组成;靠热影响区侧的熔合区组织粗大、晶界和Mg17Al12共晶相逐渐模糊;热影响区组织形貌与母材相近,但晶粒有明显长大现象。