摘要
通过单向超塑性拉伸试验,研究了供应态LY12铝合金棒材超塑性变形中空洞的形成和发展过程及其应变速率对空洞演变的影响、空洞对超塑性变形能力的影响等。研究结果表明,供应态LY12铝合金在超塑性变形过程中产生的空洞主要是O型和V型空洞,分别产生于三叉晶界处、第二相粒子附近和晶界内,这些空洞可能导致晶界的不协调滑动;在低应变速率条件下,由于粘性层较厚,使晶界滑移很容易进行,LY12铝合金的超塑性变形能力较高,但试样断面上产生较多的空洞,使试样室温性能恶化;在高应变速率条件下,LY12铝合金具有较好的超塑性和室温性能。分析认为,在高应变速率条件下,晶界上的粘性层很薄,在晶粒的相互挤压和转动中很容易细化,使材料的超塑性变形能力增强;在超塑性变形中的空洞,可以看成是保证得到高塑性所必需的组织成分。一定程度的空洞并呈细小而分散状独立存在时,对晶界滑动是非常有利的。
In this paper, superplasitic uniaxial tensile tests of coarse-grained LY12 alloy were conducted. The deforming and development process of cavity, the influence of strain rate on cavity evolvement, the influence of cavity on superplastic deformation capability were investigated. The results show that. The pore nucleation occurs not only at triangle grain boundaries, but also along nearby the second phase particle, and even within grains. The cavities at the triangle grain boundaries are presented in Vshape, others near the second phase particle and within grains are presented in O-shape. These cavities may result in disharmony slippage of grain boundaries. In lower strain-rate condition, because nearly all grains are covered with thick viscous layer which can optimize superplastic characteristic and is as a result of grain boundary sliding. In this case, though LY12 alloy has better superplastieity, many big cavities in the specimen can reduce the room temperature properties of the alloy. In higher strain-rate condition, LY12 alloy has good superplasticity and room temperature properties. By analyzing, viscous layer on grain boundaries is very thin and grain sizes can be refined during their extruding and rotating each other in higher strain-rate condition. Growth and coalescence of cavity are the main reason of the superplastic fracture of LY12 alloy, And small and certain cavities with dispersion and independence state are very useful to crystal boundary slippage.
出处
《塑性工程学报》
EI
CAS
CSCD
北大核心
2007年第1期27-30,35,共5页
Journal of Plasticity Engineering
