电磁搅拌对镁合金AZ91D初生相形貌的影响及机理

Effect & Mechanism of Electromagnetic Agitation in Primary Phase of AZ91D Alloy

研究了不同电磁搅拌工艺下镁合金AZ91D初生相α-Mg的形成过程及机理。结果表明:在不同的搅拌工艺下初生相的形成过程及机理是不同的。当金属液冷却到固液两相区后开始搅拌时,由于此时已形成大量的树枝晶初生相,影响初生相形貌的主要机制是:搅拌冲击作用使初生枝晶发生弯曲变形直至机械断裂;当金属液温度高于液相线开始搅拌时,主要机制是:搅拌使合金熔体内各处温度均匀,形核可在整个熔体内同时进行,且搅拌使正在生长的初生相枝晶臂大量熔断。此外还对电磁搅拌过程中金属液的受力和流动进行了分析。

The mechanism and formation of morphology of the primary phases α-Mg for AZ91D alloy under the different technologies of the electromagnetic agitation have been studied,resulting in that different mechanism and formation of morphology of the primary phase from different agitating technology.When it was started at the moment the molten metal cooled from the temperature above liquids to two phases zone,owing to here forming large numbers of dendritic primary phases the main phenomena influencing morphology of the primary phases were of bending deformation of primary dendritic and dendritic mechanical fracture under the impact of agitating;When the electromagnetic agitating was started at the temperature above liquids,the main phenomena were that electromagnetic agitating made uniform temperature everywhere inside the molten metal,nucleation of primary crystals simultaneously proceeded in the whole melt and numerous primary dendritic arms broken caused by such agitation.In addition, stress and flowage of the melt metal in the process of electromagnetic agitation have been also analysed.