摘要
7475高强铝合金经过由固溶处理、轧制、再结晶组成的形变热处理工艺细化晶粒后,在适当条件下变形可呈现出良好的超塑性。在最佳变形条件下(T=510℃,ε_0=8.33×10^(-4)S^(-1)),获得最大延伸率为1700%。显微组织观察表明:Ⅲ区变形机制以晶间滑移为主,在晶内形成了位错亚结构。Ⅱ区的变形机制为晶界滑移伴随晶内位错运动。位错密度随应变的增加而增加。在Ⅰ区变形以扩散蠕度为主不包括晶间滑移。超塑变形Ⅱ区的激活能接近于体扩激散活能。
After grain refinement by the thermomechanical treatment,which is co- mposed of solution treatment,warm roiling and recrystallization,the 7475Al alloy exhibits excellent superpleaticity under some suitable deformation conditions.The maximum elongation of 1750% was obtained under the op- timum deformation condition(T=510℃=8.33×10^(-4)s^(-1).The observation of microstructral changes shows that deformation in region Ⅲ is caused by int- ragranular slip which leads to dislocation substruiture formation,and defor- mation in region Ⅱ by grain boundary sliding which is accommodated by intr- agranular dislocation motion,The dislocation density increaes with increasing of strain level.Deformation in region Ⅰ is developed by diffusion creep and not involved with interagranular slip.The activation energy Q for superplastic flow is close to that for lattice diffusion in this alloy.The lattice diffusion in the matrix may be the rate controlling process of superplastic deformation of the alloy.
关键词
高强
铝合金
超塑性
晶界
滑移
7475Al alloy
superplasticity
grain boundary sliding
activation energy
