Microstructure And Mechanical Properties Of Mg–Al-Sn-Mn Magnesium Alloy Sheets

Magnesium alloy sheet have a wide application prospect in electronics, communications, transportation, aerospace, defense industry and other fields. But the application is very limited due to the output, consumption and alloy grades are far less than other nonferrous metal like steel, aluminum and copper etc. This is mainly due to the poor plastic deformation of magnesium alloy at room temperature. This reason make magnesium alloy sheet preparation process complicate, processing difficult, high cost and poor performance. Therefore, How to improve the mechanical performance of magnesium alloy sheet and reduce processing cost is the most important problems in the researchs of magnesium alloy sheet.For the purpose of developing low cost and high performance magnesium alloy sheet, this research studied the influence of the different Al, Sn element content on the alloy sheet prepared by conventional extrusion and extrusion-rolling process and the mechanism of Al, Sn element content changes impacted the microstructure and mechanical properties. The results are mainly concluded as follows:① The grain size of as-extruded Mg-Al-Sn-Mn alloy sheet was increased with the increase of Al element content increased, and decreased with the increase of Sn content of elements. The Mg-5Al-1Sn-0.3Mn alloy can be further refined after annealing. The number of the second phase increased with the increase of the Al, Sn element content, the main second phase in the alloy sheet is composed of Mg17Al12 and Mg2 Sn. The texture type of sheets is the typical basal texture and the intensity of basal texture is first increased and then decreased with the increase of Al content. the intensity of basal texture is decreased with the increase of Sn content.② The mechanical properties along the extrusion direction of as-extruded Mg-Al-Sn-Mn alloy sheet are increased with the increase of Al, Sn element content. The Mg-5Al-1Sn-0.3Mn and Mg-5Al-3Sn-0.3Mn alloy sheets exhibited the best mechanical properties which yield strength reached 142 MPa and 147 MPa; Tensile strength reached 282 MPa and 290 MPa; fracture elongation rate reached 22.7% and 22.7%, respectively. The strengthening mechanism are mainly solid solution strengthening, second phase strengthening and texture enhancement. The mechanical behaviors of annealed Mg-5Al-1Sn-0.3Mn has been further improved, the yield strength increased to 186 MPa, the tensile strength increased to 304 MPa, elongation rate changes little. The reason of this phenomenon is the fine grain strengthening and texture strengthening. The mechanical property anisotropy of as-extruded Mg-Al-Sn-Mn alloy sheet decreased with increasing Al element content when Sn element content is constant, and increased with the increase of Sn element content.③ Mg-Al-Sn-Mn alloy rolled sheet has an obvious recrystallization in hot rolling process, the grains were elongated along the rolling direction, the second phase was broken during the rolling process and the distributionalong the rolling direction, The texture type after rolling process is the basal texture and the texture intensity decreased with the increase of Al, Sn element content.④ The yield strength, ultimate tensile strength and fracture elongation of roll-annealed Mg-Al-Sn-Mn alloy sheets were increased with the increase of Al element content, and when the Sn element content changes the change of machnical properties is not obvious. The Mg-5Al-1Sn-0.3Mn and Mg-5Al-3Sn-0.3Mn alloy sheets exhibited the best mechanical properties which yield strength reached 223 MPa and 233MPa; Tensile strength reached 313 MPa and 324 MPa; fracture elongation rate reached 25.2% and 24.1%, respectively. The strengthening mechanism are mainly grain refining, solid solution strengthening, second phase strengthening and texture enhancement. The mechanical property anisotropy of roll-annealed Mg-Al-Sn-Mn alloy sheets decreased with increasing Al element content.⑤ This paper found Mg-Al-Sn-Mn alloy prepared by extrusion, rolling and annealing treatment exhibit high performance and low cost, the mechanical properties significantly better than current commercial magnesium alloy sheets. The Mg-Al-Sn-Mn alloy sheet has the potential of engineering application.