Abstract:
Intermetallic phases play a major role in the creep behavior of Mg alloys. The effects of intermetallic
phases on the creep behavior of AZ91 alloy have been studied in the present investigation. Thermally
stable and finer intermetallic phases such as Mg2Si and Mg3Sb2 are introduced deliberately in AZ91 alloy
by the addition of Si and Sb (0.5% Si, 0.5% Sb and 0.5% Si + 0.2% Sb, all are in wt%). Creep tests were carried
out at 150 ◦Cand 200 ◦Cwith an initial stress of 50MPaon the as cast samples. The detailed microstructural
analyses carried out on the crept samples indicate that the -Mg17Al12 intermetallic phase in the AZ91
alloy suffers sever cracking and facilities cavity formation due to its low melting point and incoherency
with Mg matrix, which results in poor creep resistance. On the other hand, the creep behavior of AZ91
alloy at 150 ◦C is greatly improved with the presence of Mg2Si or Mg3Sb2 intermetallic phases because of
their better thermal stability than Mg17Al12. These intermetallic phases strengthen the grain boundary
against sliding and hence, reduce the possibility of void formation during creep. Furthermore, it also
promotes more number of continuous Mg17Al12 dynamic precipitates near the grain boundary during
creep, which in turn restricts the creep deformation
