Evaluation of plastic working properties of fine grained aluminum alloy

本研究的目的是利用热多轴交替锻造（MAF）方法改善和评价过度细晶组织材料的塑性加工性能和生产工艺，MAF是一种硬质应变诱导方法，旨在提高铝合金的强度。2002年*发明亚微米级晶粒微观组织的板材材料，采用温多轴交替锻锻轧制的组合加工工艺，取得了足够的成功。*为评价细晶结构材料的塑性加工而制作的双轴拉伸试验机，经检验，该机具有足够的拉伸试验机精度，其规格如下：（载荷；5kn，行程；120mm，应变率；10^<-5> ~ 10^3，温度；~ 600℃，试样形状；十字形）。同时，确定了十字形试样的最佳形状和尺寸。2003 *所生产的十字形试样在高温变形的双轴应力条件下，塑性变形可达80%以上。*在单轴应力下，m值随应变率的增加而减小，但在双轴应力下，m值保持在0.30以上，达到1.7 × 10^<-1>s^<-1>，为高应变率。*对于相同晶粒尺寸的试样，在单轴和双轴应力作用下，许多力学特性表现出明显的差异。在673K退火温度下，单轴和双轴应力下的n值分别为0.33和0.26。*在单轴和双轴应力条件下，晶粒尺寸对力学性能的影响是不同的。*在实验温度673K，应变率8.3 × 10^<-2>s^<-1>下，在无剪切变形的双轴应力下，改变约60%后，也进行了动态再结晶测试。*在673K温度下，单轴应力下晶粒沿拉伸方向发育，空洞沿拉伸方向垂直出现，但在双轴应力下，变形晶粒形状保持等轴变形，空洞向任意方向产生。由于细晶材料超塑性变形中变形情况随加载应力状态而变化，因此在变形模拟中有必要使用双轴应力下的工作加工评价参数进行工作加工条件推定。少

The purpose of this research is to improve and evaluate the plastic working properties and production process of material which overly has a fine grained structure using the warm multi-axial alternative forging (MAF) method which is one of some hard strain induced methods due to enhancement of the strength of aluminum alloy.2002 * The invention of board material which has microstructure with sub micrometer grain size was able to achieve sufficient success according to the combination processing process of warm multi-axial alternative forging forge and rolling. * The bi-axial tension testing machine made as an experiment for evaluation of the plastic processing of material with fine grained stricture and it checked that this machine had accuracy sufficient as tensile testing machine with specification as following : (Load ; 5 kN and Stroke ; 120mm, Strain rate ; 10^<-5>〜10^3, Temperature ; 〜600℃, Shape of specimen ; cruciform). Moreover, the optimal form and size of cruciform specimen u … More sed were determined.2003 * The produced cruciform specimens can give plastic deformation of 80% or more in conditions of bi-axial stress under high temperature deformation. * Although m value decreases with the increase in strain rate under uni-axial stress, that value maintains 0.30 or more to 1.7 x 10^<-1>s^<-1> which is high strain rate under bi-axial stress. * For same grain sized specimens, the difference of many mechanical characteristics appeared notably under uni-axial and bi-axial stress. In annealing temperature 673K in which the difference produced, n values were 0.33 and 0.26 under a uni-axial and bi-axial stress respectively. * The effect of grain size on mechanical properties is different for condition under uni-axial and bi-axial stress. * At experimental temperature 673K and strain rate 8.3 x 10^<-2>s^<-1>, the dynamic re-crystallization was checked also under bi-axial stress without shear deformation after changing about 60%. * Although a crystal grain develops in the tensile direction and voids arise perpendicularly to the tensile direction under uni-axial stress at temperature 673K,the shape of deformed grain maintains the situation of equiaxial distortion for bi-axial stress and voids produces to arbitrary directions.Since the situation of deformation changes with loading stress states in the superplasticity deformation using fine grained material, it is necessary to use the work processing evaluation parameter under bi-axial stress in the deformation simulation for work processing condition presumption. Less