Creep Behavior of As-Cast Mg-10 wt.%Sn and Mg-10 wt.%Sn-3 wt.%Al-1 wt.%Zn Alloys: A Comparative Study

Abstract

The present investigation highlights the creep deformation and rupture behavior of indigenously produced as-cast Mg-10 wt.%Sn-3 wt.%Al-1 wt.%Zn (TAZ1031) and Mg-10 wt.%Sn (T10) alloys. Conventional creep tests were conducted at 423 K (150 degrees C) in the stress range of 30-45 MPa and at 45 MPa in the temperature range of 423-453 K (150-180 degrees C) for both the alloys. The nature of creep curves was found to be identical for both the alloys with short primary and secondary creep regime, followed by extended tertiary creep region. The creep resistance of the TAZ1031 alloy was better than the T10 alloy. The former exhibited reduced minimum creep rate and enhanced creep rupture life under identical creep test conditions with respect to the latter. The change of minimum creep rate (epsilon(min)) followed a power-law relationship with a change in applied stress (sigma) for both the alloys with a significant change in stress exponent (n) value. Activation energy for creep deformation of TAZ1031 alloy (similar to 117 kJ/mol) was found to be higher than T10 alloy (similar to 105 kJ/mol). Fine secondary Mg2Sn precipitates within the alpha-Mg matrix and primary Mg2Sn, Mg17Al12 and MgZn2 precipitates along the grain boundaries improved the creep properties of TAZ1031 alloy. On the contrary, the threshold stress required for creep deformation was found to be significantly low in TAZ1031 alloy due to the presence of Mg17Al12. Both creep damage analysis and dimpled fracture surfaces revealed necking dominated creep deformation for the alloys. SEM studies revealed the absence of creep cavities along grain/dendritic boundaries for the investigated alloys, which substantiated the formation of dimpled fracture surfaces during creep deformation.