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The microstructural evolution and phase transformations of mechanically stirred non-dendritic ZA27 alloy during partial remelting were studied by using scanning electron microscopy and X-ray diffraction technique.The partial remelting temperature was 460℃ and lower than the stirring temperature of 465℃.So the microstructure with globular grains needed for semi-solid forming can not be obtained and the starting primary non-dendritic grains change in turn to connect non-dendritic grains, long chain-like structures and finally to coarsen connect grains.However,the small near-equiaxed grains between the primary non-dendritic grains are evolved into small globular grains gradually,some of which are also attached to the primary non-dendritic grains during the subsequent heating.The X-ray diffraction results show that a series of phase transformations, α+η+ε→β,η+β→L,β→α′+L,α+η+ε→α′ and α′→L, occur successively during this process.The main reason why the starting primary non-dendritic grains do not separate into the needed independent globular grains is that the reactions of η+β→L and α′→L do not occur or occurr incompletely in the layers used to connect the primary non-dendritic grains.
The microstructural evolution and phase transformations of mechanically stirred non-dendritic ZA27 alloy during partial remelting were studied by using scanning electron microscopy and X-ray diffraction technique. The partial remelting temperature was 460 ° C and lower than the stirring temperature of 465 ° C. So the microstructure with globular grains needed for semi-solid forming can not be obtained and the starting primary non-dendritic grains change in turn to connect non-dendritic grains, long chain-like structures and finally to coarsen connect grains. Still, the small near- equiaxed grains between the primary non-dendritic grains are evolved into small globular grains gradually, some of which are also attached to the primary non-dendritic grains during the subsequent heating. X-ray diffraction results show that a series of phase transformations, α + η + ε → β, η + β → L, β → α ’+ L, α + η + ε → α’ and α ’→ L, occur successively during this process.The main reason why the start ing primary non-dendritic grains do not separate into the needed independent globular grains is that the reactions of η + β → L and α ’→ L do not occur or occurr incompletely in the layers used to connect the primary non-dendritic grains.