Microstructural evolution of previously deformed ZA27 alloy during partial remelting

The microstructural evolution process of previously deformed ZA27 alloy during partial remelting was studied. After being compressed by a ratio of 20% in length at 250 degreesC, the microstructure of ZA27 alloy changed from developed dendrites to coarsened short dendrites and near-equiaxed grains, then in turn to united pieces. big lumps, small pieces, polygon particulates, and finally to spherical grains that would grow and agglomerate and become larger in size and irregular in shape during following partial remelting at semi-solid temperature of 460 degreesC. The structure evolution resulted from the eutectics first melted between boundaries of the primary grains and then penetrated into polygon boundaries that formed due to recrystallization, resulting in the separation of the primary grains into small polygon grains, followed by spheroidizing. This process was mainly discussed through analyzing the phase transformations occurred during partial remelting. (C) 2002 Elsevier Science B.V. All rights reserved.