Abstract: Phase transformation and microstructural change of an as-cast ZA27 alloy were in-vestigated during compressive creep by X-ray diffraction technique, SEM and TEM. Compressive creep induced decomposition of a metastable η' phase and a four-phase transformation, α + ε → T' + η and T' →θ7 occurred during the compressive creep testing. The occurrence of negative creep in the alloy resulted from the volume ex-pansion caused by the four-phase transformation. A microstructural change was also observed from a lamellar structure into a spheroidized structure in higher creep strain of tested specimens. It provided evidence of compressive creep induced phase trans-formation which occurred in ageing process.

Key words: microstructure change, compressve creep, ZA27 alloy