The elevated-temperature mechanical behavior of peak-aged Mg-10Gd-3Y-0.4Zr Alloy

Mg-10Gd-3Y-0.4Zr (wt.%) was peak-aged (solution heat-treatment at 490 degrees C/8 h with subsequent aging at 250 degrees C/16 h) and tested in tension and compression at temperatures between 25 degrees C and 350 degrees C, in fatigue at 25 degrees C and 300 degrees C, and in tensile creep at 250 degrees C and 300 degrees C. The tensile and compression testing showed high values of ultimate tensile stresses (UTS) and compressive peak stresses, both of which were above 300 MPa at temperatures up to 250 degrees C. At temperatures higher than 250 degrees C, the peak stresses rapidly decreased. The fatigue experiments indicated that the fatigue lives were not sensitive to temperatures between 25 and 300 degrees C. The fatigue limit was between 50 and 75 MPa. The creep experiments suggested that in the applied stress range of 30-120 MPa the dominant secondary creep deformation mechanism was dislocation climb. The dense distribution of precipitating prismatic particles in the matrix of the magnesium solid solution aided the creep resistance. In the lower-temperature and lower-applied stress creep regime (e.g. longer creep life), intensive creep cavitation was observed at the grain boundaries in the form of cavitated grain facets and a high fraction of cavitated boundaries (similar to 45%). In the higher-temperature and higher-stress creep regime, failure occurred in the form of mixed grain boundary cavitation and cracking. In both cases the preferred cavity and crack nucleation sites were particles of secondary phases situated on the grain boundaries or triple junctions. (C) 2011 Elsevier B.V. All rights reserved.