Inter-granular liquid phase aiding grain boundary sliding in superplastic deformation of fine-graine

• 作 者: LEE Shyong CHIANG Chih-te HSU Chang-chuan
• 机 构: Department of Mechanical Engineering,National Central University,Chun-Shan Institute of Science,
• 出 处: Transactions of Nonferrous Metals Society of China
• 发表日期: 2010年S2期
• 关键词: sliding granular appearance elongation initially fractured extrusion microscopic

For 7475 Al alloy,there were micrographs showing filaments or whiskers formation during the separation stage of superplastic elongation.This indicates the presence of liquid phase which accommodates grain boundary sliding to reach superplasticity.On the other hand,there is no such phenomenon reported regarding Mg alloy in literatures.Scanning electron microscopic(SEM)fractography exceptionally exhibits a mark of grain boundary sliding and its accommodating mechanism of inter-granular liquid phase.Under the testing conditions of 350℃ and 1×10- 4s -1,the initially fine-grained structure(3.7μm)yields 642%superplastic elongation and exhibits fluffy appearance on the fractured surface.For other specimens showing less superplasticity,their fractured surfaces exhibit partial fluffy appearance.

For 7475 Al alloy, there are micrographs showing filaments or whiskers formation during the separation stage of superplastic elongation. This is the presence of liquid phase which accommodates grain boundary sliding to reach superplasticity. On the other hand, there is no such phenomenon reported regarding Mg alloy in literatures. Scanning electron microscopic (SEM) fractography exceptionally exhibited a mark of grain boundary sliding and its suspension mechanism of inter-granular liquid phase. Bunder the testing conditions of 350 ° C and 1 × 10 -4 s -1, the initial fine- grained structure (3.7μm) yields 642% superplastic elongation and exhibits fluffy appearance on the fractured surface. For other specimens showing less superplasticity, their fractured surfaces exhibit partial fluffy appearance.