Mg-x%Zn-(Al)合金显微组织及力学性能

Microstructure and Mechanical Properties of Mg-x%Zn-(Al) Alloy

利用光学显微镜、X射线衍射仪、扫描电镜和万能力学试验机研究了Mg-x%Zn(5、7、9、15和20%)二元合金和Mg-7Zn-4Al合金的显微组织及力学性能。结果表明:Mg-Zn合金铸态显微组织主要由α-Mg和沿晶界分布的Mg7Zn3共晶相组成。随着Zn含量的增加,Mg-Zn二元合金的抗拉强度呈先上升后下降的趋势,而伸长率呈逐渐下降的趋势。当Zn含量为7%时,合金的抗拉强度达到最大,为213.3 MPa;当Zn含量高于9%后,合金的抗拉强度和伸长率急剧下降。在Mg-7Zn基体合金中添加4%Al后,合金的显微组织主要由α-Mg和Mg3(2Al,Zn)49三元共晶相组成。合金的铸态力学性能相对于基体有所下降,但是热处理后抗拉强度得到显著提高,为305 MPa,相对铸态提高了57.8%。Mg-Zn合金中添加Al元素有利于合金的热处理强化。

The microstructure and mechanical properties of Mg-x% Zn （5%, 7%, 9%, 15% and 20%） binary alloys and Mg-7Zn-4A1 alloy were investigated by optical microscope （OM）, X-ray diffraction （XRD）, scanning electron microscope （SEM） and universal testing machine. The results indicate that the microstructures of Mg-Zn binary alloys consist of tx-Mg matrix and MgTZn3 on grain boundary. The tensile strength of alloys rises first and descends later with increasing the Zn content, while the elongations gradually decrease. The maximum value of tensile strength is 213.3 MPa with addition of 7% Zn; the tensile strength and elongation are significantly decreased when added more than 9% Zn content. Added 4% A1 to Mg-7Zn matrix alloy, the microstructures consist oftx-Mg matrix and Mg32（AI, Zn）49 ternary eutectic phase. Compared to Mg-Zn binary, the tensile strength of as-cast Mg-7Zn-4A1 alloy has declined, but it is enhanced significantly after heat treatment, the value has increased by 57.8% to 305 MPa. Consequently, the addition of A1 to Mg-Zn alloy is beneficial to heat treatment strengthening.