Microstructure and Yield Asymmetry Behavior of Indirect-extruded Mg-Sn-Al-Zn Alloys

Abstract

Mg-(9-x)Sn-xAl-1Zn (x=1, 2, 3 and 4 wt.%) alloys were subjected to indirect extrusion, and the microstructure and mechanical properties of the as-extruded Mg-Sn-Al-Zn (TAZ) alloys were investigated. The TAZ 811 alloy exhibited a finer grain structure than the TAZ 541 alloy due to a larger number of Mg 2 Sn particles, which pinned the grain boundaries and prevented growth of recrystallized grains. The TAZ alloys showed an unusual yield asymmetry behavior. The tensioncompression yield asymmetry increased with decreasing average grain size. The TAZ 811 alloy with a small grain size exhibited a larger yield asymmetry than that of the TAZ 541 alloy having a relatively large grain size, which is mainly attributed to the low Al content and large number of second phase particles in the TAZ 811 alloy.

Effect of cold pre-forging on the microstructure and mechanical properties of extruded Mg–8Sn–1Al–1Zn alloy

“…Furthermore, it has been recently reported that fine precipitates formed during extrusion play a significant role in suppressing grain growth through pinning, thereby resulting in a remarkably refined grain structure [18]. Hence, grain boundary pinning by the dispersed Mg 2 Sn precipitates evident in the micro-beam diffraction pattern will also contribute to the formation of an ultrafine grain structure; the shape and size of these Mg 2 Sn precipitates are consistent with previous results relating to indirectly extruded TAZ811 alloys [5,19]. The 10% CPF extruded alloy exhibits excellent tensile properties with a TYS of 387 MPa, a UTS of 403 MPa, and an EL of 7.9%, which are significantly higher than the 343 MPa TYS, 363 MPa UTS, and 6.4% EL of the non-CPF extruded alloy.…”