Elevated temperature deformation of Cr3Si alloyed with Mo

Four-point bend, constant load compressive creep and constant engineering strain rate tests were conducted on are-melted and powder-metallurgy (PM) processed Cr40Mo30Si30 specimens in the temperature range 1400-1700 K. This is a two-phase alloy consisting of (Cr,Mo)(3)Si and (Cr,Mo)(5)Si-3 phases. The PM specimens, which were substantially weaker than the are-melted materials, exhibited a stress exponent, n, of about 2 and an apparent activation energy for creep, Q(a), of 485 kJ/mol. The mechanism in these specimens appeared to be controlled by creep of a glassy phase. In the case of are-melted specimens for which n ' 3 and Q(a) ' 430 kJ/ mol, the rate-controlling creep mechanism appeared to be that dominant in the (Cr,Mo)(5)Si-3 phase. In this case, it is suggested that the Nabarro creep mechanism, where dislocation climb is controlled by Bardeen-Herring vacancy sources, is the dominant creep mechanism. Finally, an analysis of the present and literature data on Cr3Si alloyed with Mo appeared to suggest that the creep rate decreases sharply with an increase in the Mo/Si ratio. (C) 1999 Elsevier Science Ltd. All rights reserved.