Microstructure evolution of Zn-8Cu-0.3Ti alloy during hot deformation
(Nonferrous Processing Division, General Research Institute for Nonferrous Metals, Beijing 100088, China)
Abstract: The hot deformation behavior of homogenized zinc alloy was investigated through uniaxial compression test on a Gleeble-1500 thermal-mechanical simulator within a temperature range of 230-380 °C and a strain rate range of 0.01-10 s-1, the corresponding flow curves and their characters were determined and analyzed, and microstructures were studied by optical, SEM and TEM microscopy. The results indicated that the microstructure evolution of zinc alloy during hot deformation involves the spheroidization of the phase of TiZn15, coarsening of the precipitated phase and dynamic recrystallization (DRX) of the phase of matrix, leading to the formation of the polyphase (η+ε+TiZn15) structure. The spheroidization of the phase of TiZn15 during hot deformation was beneficial to the particle nucleation stimulated and then promoted to DRX of matrix. The dynamic recrystallization grain size of the matrix phase decreased firstly and then increased with elevating the temperature, and the degree of DRX became more complete when the strain rate and strain became larger. Hot deformation accelerated the diffusion of Cu atom, which resulted in the coarsening of the precipitated phase. Thus, the microstructure was refined owing to the pinning effect of the precipitated phase.
Key words: zinc alloy; dynamic recrystallization; high temperature deformation; polyphase alloy