Negative creep during compressive creep of as-cast ZA27 alloy

The negative creep during compressive creep deformation of as-cast ZA27 alloy was investigated at the temperature range of 20-160degreesC and at compressive stress levels from 50-137.5 MPa with special apparatus. Results show that the negative creep in the alloy occurred respectively at 20 V (50 MPa, 87.5 MPa and 100 MPa), 60degreesC (50 MPa and 87.5 MPa) and 100degreesC (50 MPa). According to the phase transformation and theoretical analysis, the negative creep resulted from volume expansion caused by four-phase transformation alpha+epsilon-->T'+eta in the alloy. The theoretical analysis is consistent with the experiment results. And the values of negative creep depended on the difference between the compressive creep deformation and the volume expansion.