Microstructures and mechanical properties of Mg–6Zn–1Y–0.85Zr alloy prepared at different extrusion temperatures and speeds

Abstract

The influence of extrusion temperature and speed on the microstructures and mechanical properties of the as-extruded Mg–6Zn–1Y–0.85Zr (ZWK610) alloy was inquired by indirect extrusion at three ram speeds (1, 3 and 6 mm/s) and extruding temperatures (250, 300 and 350 °C). The extruded alloy organization mainly consists of equiaxed finely dynamic recrystallized (DRXed) grains, elongated coarse un-DRXed grains and massive W–Mg3Y2Zn3 and I–Mg3Zn6Y phases. The increasing extrusion temperature and speed result in larger DRXed grains, higher DRXed volume fractions and fewer second phase volume fractions. Mechanical properties drop with increasing extrusion temperature and speed. The extruded alloy prepared at low temperature and speed reveals a lower DRXed volume fraction, a finer DRXed grain size and a higher phase volume fraction because a large number of depressively distributed particles could inhibit the grain boundary migration and pin the dislocations effectively. Excellent mechanical properties were acquired at 250 °C and 1 mm/s, with ultimate tensile and tensile yield strengths of 410 MPa and 365 MPa, respectively, while the elongation is 7.1%.