Research Of Mg-Al-Zn Alloys On Microstructure, Mechanical Properties And Fracture Behavior

Al and Zn are economical and effective elements to strengthen magnesium alloys.So Mg-Al-Zn alloys are one of the most widely-used magnesium alloys.The phase composition,microstructure,fracture behavior and mechanical properties such as tensile strength,elongation of Mg-Al-Zn alloys are investigated by X-Ray diffractometer,optical microscope,electron probe microanalyzer and mechanical apparatus.The purpose of this paper is for the further development of research based on the theory and practice of Mg-Al-Zn alloys.The main compounds of Mg-Al-Zn alloy are a-Mg phase,β-Mg₁₇Al₁₂ phase,Ï„-Mg₃₂(Al,Zn) ₄₉ phase and Mg-Zn phase.The ratio of Al and Zn determines the phase composition of Mg-Al-Zn alloys.After heat-treatment the metal-compounds in the grain boundary or inside are solution again to make the grain boundaries become clear.The re-precipitation phase composition could hinder the dislocation slip in aging process.According to the structure photos and mechanical properties test results show that the mechanical properties reach the best when the contents of Al and Zn are 6%. The tensile strength of Mg-6%Al-6%Zn is 233MPa.It reached up to 252MPa after heat treatment.The plastic of Mg-3%Al-l%Zn is acceptable.The elongation and section shrinkage is 11.7%and 11.5%.After heat treatment the plastic of Mg-3%Al-l%Zn such as elongation and section shrinkage is 12.4%and 18.1%.Photographs of fracture surface showed that the main features of AZ3 1 is the smaller cleavage face and river pattern.The fracture behavior of AZ11 almost can not see off the rivers cleavage patterns.The fracture appeared to be very messy.