离心压力和冷却速度对AZ91镁合金凝固组织的影响

旨在优化AZ91镁合金凝固组织,通过OM和XRD设备研究了不同离心压力和冷却速度对AZ91镁合金凝固组织演变的影响,结果表明,随着离心压力的增大,合金晶粒尺寸细化,第二相β(Mg12Al17)析出量减少,不保温试样,β相形态由粗大连续网状向细小断续状转变,保温试样,β相为粒状弥散分布晶内,压力增大,颗粒数量减小,粒径细化.同等凝固压力下,增大冷速,一次β相析出量增多,二次β相析出量减少.XRD分析表明,增大离心压力β相峰值略微减弱,α-Mg的晶格常数减小.

Effect of centrifugal pressure and cooling rate on solidification microstructure of AZ91 alloy

Solidification microstructure evolution of magnesium alloy AZ91 under different centrifugal pressure and cooling rate were explored through OM and XRD to optimize solidification microstructure of AZ91 alloy , With the increasing of centrifugal pressure, the grain size and precipitation of second phase β-Mg12 Al17 was decreased, the morphology of β turned from coarse continuous networks to thin interruption in the sample without heat preservation, while in the sample with heat preservation, granular β phase distributed within the grains. The number of β was reduced ,and the size of βwas refined with increasing centrifugal pressure. With the increase of cooling rate under same pressure, more primary β precipitated, but less secondary β precipitated. Result of XRD showed that the peak value of β weakened slightly and the lattice constant ofα-Mg decreased with increasing pressure.