Fine equiaxed dendritic structure of a medium carbon steel cast using pulsed magneto-oscillation melt treatment

The application of a pulsed magneto-oscillation （PMO） technique during the solidification of a commercial high melting point medium carbon steel ingot （φ0140 mm × 450 mm） produced fully equiaxed grains in the cast ingot, indicating that the PMO process significantly promotes heterogeneous nucleation near the solid-liquid interface. The vigorous convection induced by PMO forced the partly solidified grains to move from the solid-liquid interface and became randomly distributed throughout the melt, which resulted in the formation of uniformly sized equiaxed dendrites throughout the whole ingot. Building on the developed nucleation mechanism and a flow field simulation of pure aluminum, a PMO-induced grain refinement model for steel is proposed.

2.5维织物C_f/Al复合材料制备及其经纬向拉伸变形力学行为研究

以石墨纤维2.5维机织物为增强体,铝合金ZL301为基体材料,采用真空辅助压力浸渗法制备了2.5维织物Cf/Al复合材料,研究了3种织物预热温度下制备的复合材料相对致密度和微观组织形貌,分析了其界面产物组成与界面结构特征,测试了其经、纬向准静态拉伸变形力学行为并分析了其断口形貌。结果表明:复合材料织物的细观结构完整,内部纤维分布均匀,致密度随预热温度提高而略有上升,界面棒状产物为Al4C3相,其相对含量随预热温度的提高而增加,从而引起复合材料经向和纬向力学性能的下降。复合材料经向拉伸强度高于纬向拉伸强度,且其应力-应变行为呈现出显著的非线性特征,复合材料经向和纬向拉伸变形过程均可划分为3个阶段:初始弹性变形阶段、中间弹塑性变形阶段和最终损伤与断裂阶段。