稀土Yb对AZ91镁合金铸态及时效态组织和性能的影响

Effects of Rare Earth Yb on Microstructure and Properties of As-cast and Aged AZ91 Alloys

采用金相观察、X射线衍射和硬度测试等方法,研究了稀土Yb对AZ91镁合金铸态及热处理态组织和性能的影响。结果表明,添加1%的Yb可细化AZ91合金铸态组织,有效抑制β-Mg17Al12相的生长,并使β相由网状变为断续分布。XRD分析表明,合金中出现新相Al11Yb3,使合金硬度增加。添加Yb使AZ91合金固溶处理后的残余化合物增加,尽管对时效峰值影响不大,但可推迟180℃时效峰值和延缓过时效的出现。

Effects of rare earth ytterbium(Yb)on microstructure and properties of as-cast and aged AZ91 magnesium alloy were investigated by OM(optical microscope),XRD(X-ray diffraction)and hardness testing.It is found that 1% Yb addition can refine as-cast structure of AZ91 alloy and effectively restrain the growth of β-Mg17Al12 phase with the transformation from net-work structure into discontinuous ones.The hardness of the alloy is increased as a result of creation of Al11Yb3 phase by XRD analysis.Residual second phase is increased with Yb addition after solution treatment,which can postpone the appearance of peak hardness in the aging curves at 180℃ and delay the occurrence of over-aging process in spite of the value of peak hardness is only slightly changed.