Zn与Mg质量比对热挤压Al-Zn-Mg-Sc显微组织及力学性能的影响

Effect of Mass Ratio of Zn to Mg on Microstructure and Mechanical Properties of Hot-extruded Al-Zn-Mg-Sc Alloys

制备了Al-2Mg-0.4Sc、Al-5Mg-0.4Sc、Al-5Mg-2Zn-0.4Sc和Al-5Zn-2Mg-0.4Sc等4种合金并在350℃进行热挤压,通过光学显微镜(OM),X射线衍射(XRD),扫描电子显微镜(SEM)、室温拉伸测试,研究了Zn/Mg比对于Al-Zn-Mg-Sc合金组织与力学性能的影响。结果表明,Zn/Mg比的提高对于铸态晶粒具有细化作用,挤压后发生动态再结晶,晶粒尺寸显著减小,但挤压态晶粒尺寸并未随Zn/Mg比的提高而减小。另一方面,Zn/Mg比的提高使Mg32(Al,Zn)49第二相数量增加,且呈现更明显的网状结构。挤压态Al-Zn-Mg-Sc合金屈服强度随Zn/Mg比的提高而提升,主要由于大量Al3Sc粒子与碎化的第二相呈网状分布于晶界,使第二相强化起到主导作用。

The effect of Zn/Mg ratio on the microstructure and mechanical properties of Al-2 Mg-0.4 Sc,Al-5 Mg-0.4 Sc,Al-5 Mg-2 Zn-0.4 Sc,Al-5 Zn-2 Mg-0.4 Sc alloys extruded at 350℃were investigated by optical microscopy(OM),X-ray diffraction(XRD),scanning electron microscopy(SEM)and tensile testing under room temperature.The results show that the increase of Zn/Mg ratio had a refining effect on the as-cast grains.Dynamic recrystallization occurred after extrusion,and the grain size significantly decreased.However,the grain size of extruded do not decrease with the increase of Zn/Mg ratio.On the other hand,the increase of Zn/Mg ratio makes the number of the second phase of Mg32(Al,Zn)49 increase and shows a more obvious network structure.The yield strength of the extruded Al-Zn-Mg-Sc alloy increases with the increase of Zn/Mg ratio,mainly because of a large number of Al3 Sc particles and the second phase of fragmentation are distributed in the grain boundary in a network,so the second phase strengthening plays a leading role.