Creep and creep rupture of a Zr-6%Sn-1%Mo alloy

Creep and creep rupture of a Zr-6%Sn-1%Mo alloy was investigated in a temperature interval 350 to 550°C using isothermal test and transmission electron microscopy techniques. The heat treatment of the alloy consisted in quenching to martensite and ageing at 550°C. The apparent activation energy of creep increases with temperature and applied stress from values lower to those significantly higher than the expected value of the activation enthalpy of the lattice diffusion to which the self-diffusion of all the three components of the solid solution (forming the matrix of the alloy) contributes. The parameter characterizing applied stress sensitivity of steady state creep rate increases with the stress from values only slightly higher than one to values close to thirty. The apparent activation energy of rupture life is close to that of creep and the stress sensitivity parameter of rupture life is close to that of steady state creep rate. The mechanisms likely to control creep rate under various external conditions are discussed. It is suggested that the mechanisms controlling the creep rate also control the rupture life.