Tensile deformation and phase transformation of furnace-cooled Zn–Al based alloy

Phase transformation and microstructural changes of the furnace-cooled (FC) eutectoid Zn–Al based alloy were studied during thermal ageing and tensile deformation using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Two types of decomposition of Zn-rich phases ηFC′ and ε were detected in both the aged and the tensile deformed alloy specimens. Precipitates of α and T′ phases were distinctly observed inside the light contrast ηFC′ and ε phases, respectively, using back-scattered electron imaging. Under tensile deformation at 150°C, the coarse lamellar structure was deformed into fine particulate structure, whilst the fine lamellar structure remained unchanged. The mechanism of tensile fracture of the alloy is discussed in relation to the stress-induced phase transformation and microstructural change. An intrinsic co-relationship of phase transformation between the aged and tensile deformed alloy specimens is also discussed.