剪切停留对液固温区A356合金组织及瞬态流变行为的影响

Influence of shear rest on microstructure of partially remelted A356 alloy and its transient rheological behavior

采用自行研制的流变装置进行瞬态流变试验 ,研究了剪切停留对液固温区不同初生α相形态A35 6合金的组织变化及其瞬态流变行为的影响 .结果表明 ,在相同的剪切条件下 ,随剪切停留时间的增加 ,瞬时峰值表观粘度增加 ,说明剪切停留期间半固态合金初生α相形态发生了变化 ;对半固态合金初生相形态观察发现 ,剪切停留促使初生相发生了“团聚”或“合并” ,而且初生相形态变化的程度取决于剪切停留时间和初生相的退化程度 .对试验结果进行曲线拟合 。

The influence of shear rest on microstructure variation and transient rheological behavior of semi solid A356 alloy with different morphologies of primary α phase was explored through the use of rest time experiment by a self designed rheometer. The results indicate that the transient peak of apparent viscosity of semi solid alloys increases with expanding the rest time under the same experimental conditions. The shear rest leads to a microstructure transformation of semi solid alloys. Microstructure observations of the semi solid alloys show that the primary α phase was agglomerated or merged during the periods of shear rest, and the structure reconstitution depends on both the periods of rest and the degree of degeneration of the primary α phase. Finally, transient rheological equations are fitted to describe the relations between peak of apparent viscosity of semi solid alloys and rest time.