Effect of Mn Content on Microstructures and Mechanical Properties of Mg-Al-Ca-Mn Alloys Fabricated by High-Speed Extrusion

Abstract

Mg-0.3Al-0.2Ca-xMn (x=0.1, 0.2, 0.4at.%) alloys were extruded at an extraordinarily high speed of 60 m/min, and the effect of Mn content on the extrudability, age-hardening response, and tensile properties was investigated. An increase in Mn content improves the surface quality of the high-speed extruded alloys. Moreover, the as-extruded Mg-0.3Al-0.2Ca-0.4Mn alloy shows much higher strengths than the as-extruded Mg-0.3Al-0.2Ca-0.1Mn alloy and also exhibits enough elongation of about 25%; the proof stress was improved from 135 MPa to 190 MPa with an increase of Mn content from 0.1% to 0.4%. Whereas the Mg-0.3Al-0.2Ca-0.4Mn alloy shows a minorage-hardening by T5-treatment compared to the Mg-0.3Al-0.2Ca-0.1Mn alloy, the proof stresses of both alloys are increased about 20 MPa. The high proof stress despite of its minor age-hardening is attributed to the strong basal texture observed in the high Mn containing alloy.