高锶含量AZ31镁合金的铸态组织及含锶相

摘要

The as-cast microstructure and Sr-containing phases in the AZ31 magnesium alloys with different Sr contents (0%, 0.3%, 2.5% and 5.0%, mass fraction) were investigated. The results indicate that after adding Sr to the AZ31 magnesium alloy, the dendrite/grain size is decreased, and with the Sr content increasing from 0 to 5.0%, the dendrite becomes finer, the dendrite morphology becomes more passive and the distribution of alloying phases at dendrite/grain boundary is dispersed. Furthermore, the morphology of the β-Mg17TAl12a phase in the alloy with addition of 0.3%Sr changes from continuously irregular strip-like shape to discontinuously irregular strip-like shape and/or fine granule-like shape. At the same time, some lamella-like eutectic phases are found in the alloys with additions of 2.5% Sr and 5.0% St, and the lamella spacing in the alloy with addition of 5.0% Sr is finer. Adding high Sr content to the AZ31 alloy can bring the new ternary eutectic and/or divorced eutectic phase of Mg11Al5Zn4 in the alloy, and the Mg17Sr2 and Mg2Sr phases are formed in the alloys with additions of 2.5% Sr and 5.0% Sr.%研究不同Sr含量(0,0.3%,2.5%和5.0%,质量分数)的Az31镁合金的铸态组织及含锶相.结果表明:在AZ31镁合金中添加Sr后,枝晶/晶粒尺寸变小,并且在0～5.0%的范围内,随着Sr含量的增加,枝晶细化且形态出现钝化现象,位于晶界/枝晶界的合金相分布更加弥散.添加0.3%Sr后,β-Mg17Al12a相从未添加Sr的AZ31合金中的连续、不规则条状转变为不连续、不规则条状和/或细小颗粒状.在添加2.5%Sr和5.0%Sr的合金中发现了一些层片状共晶相,且后者的层片间距更加小.较高含量的Sr添加到AZ31镁合金中可以形成一种新的共晶和/或离异共晶三元Mg11Al5Zn4相,在添加2.5%Sr和5.0%Sr的合金中发现了Mg17Sr2相和Mg2Sr相.