Hot workability of magnesium alloys

摘要: For the alloy AZ91 (Mg-9.OAl-0.7Zn-0.13Mn) die cast specimens were subjected to torsion testing at 150, 180, 240, 300, 420 and 450C 0.05 0.5 5.0 s -1 The as-cast exhibited hot shortness 360C above; however in that domain, after prior thermomechanical processing (TMP) 300C, they showed much improved properties (which reported along with 300C below). AZ31-Mn (Mg-3.2Al-1-1Zn-0.34Mn), AZ31 (Mg-2-8Al-0-88Zn-0.01Mn), AZ63 (Mg-5-5Al-2.7Zn-0.34Mn) ZK60 (Mg-5.7Zn-0.65Zr-O-O1A]), range 180 0.01, 0.1, 1.0 . In temperature below flow curves rise a peak failure occurring immediately thereafter. Above gradual decline towards steady state. strain rate dependence of strength is described by sinh-Arrhenius equation Q HW between 125 144 kJ/mol; this indicates control climb comparison creep 200-400C. activation energy declined order AZ63, AZ91, ZK60, while ductility increased decreasing strength. working Mg alloys from 150 450C, harden work soften state regime above 300C. At temperatures twinning observed initially bring grains into more suitable slip orientations. high T substructure develops due basal prismatic slip, Forming cells augmented misorientation first near grain boundaries later cores. Near peak, new appear old (mantle) as result dynamic recrystallization DRX but not core initial grains. As rises, are larger mantle broader, enhanced results higher ductility. intermediate T, shear bands form through alignment zones resulting reduced sizes misorientation. Dynamic does become general Cu or Ni, thus it markedly raise Retention worked substructure, refined grains, improves product.