摘要
从低压铸造后的A356.2铝合金铸旋轮毂的旋压坯料中取样,利用电子万能试验机进行高温拉伸试验,研究应变速率在0.0001～0.1 s-1,变形温度在573～673 K范围内该合金的高温拉伸流变行为。使用光学显微镜分析低压铸造后的原始铸态组织与拉伸断口处的显微组织。结果表明应变速率与变形温度对该合金的流变行为有显著影响,流变应力随温度的降低与应变速率增加而上升;伸长率随变形温度的升高和应变速率的减小而增大。变质处理后的A356.2铝合金中共晶体与α-Al枝晶分布均匀,共晶硅呈点状或蠕虫状。温度为573 K时的拉伸断口附近的金相组织没有发生明显变化,而673 K时的拉伸断口处的金相组织呈现出明显的塑性变形现象。A356.2铝合金的高温拉伸流变行为可以用Zener-Hollomon参数模型描述。通过线性回归计算出变形激活能Q=317.43 k J·mol-1,材料常数A=1.558×1023 s-1,n=7.94,α=0.0165 MPa-1,得出A356.2铝合金Arrhenius方程;利用双曲正弦模型建立了高温拉伸条件下的流变应力本构模型。
The tensile flow stress behavior of A356. 2 aluminum alloy at elevated temperature was investigated on electronic tensile testing machine over a range of stain rate 0. 0001-0. 1 s-1 and deformation temperature 573-673 K,specimens were taken from the spinning blank of cast-spinning wheels after low-pressure casting. The original as-cast microstructures after low-pressure casting and the microstructures of tensile fractures were analyzed by optical microscope. The results demonstrate that the strain rate and deformation temperature have significant effect on the flow behavior of this alloy,the flow stress increases with the decrease of temperature and the increase of strain rate,the elongation increases with the increase of temperature and the decrease of strain rate. Eutectics and α-Al dendritic crystal are homogeneously distributed in the modified A356. 2 aluminum alloy,and eutectic Si presents as spot or worm. The microstructures of the tensile fracture at 573 K have little change while the microstructures of the tensile fracture at 673 K show obvious plastic deformation.The flow tensile behavior of A356. 2 aluminum alloy at elevated temperature can be represented by Zener-Hollomon parameter model. It is calculated by linear regression that the deformation activation energy is Q = 317. 43 k J·mol-1,the material constants are A = 1. 558 ×1023 s～（-1）,n = 7. 94,α = 0. 0165 MPa-1,the Arrhenius equation of A356. 2 aluminum alloy is obtained and the constitutive model of flow stress under elevated temperature tensile condition is established by hyperbolic sine model.
作者
饶国举
李新和
孙晓冬
李昌海
朱志华
孙钡
RAO Guo-ju;LI Xin-he;SUN Xiao-dong;LI Chang-hai;ZHU Zhi-hua;SUN Bei(Light Alloy Research Institute, Central South University, Changsha 410083, China;Chang＇an Ford Automobile Co., Ltd., Chongqing 401122, China;CITIC Dicastal Co., Ltd., Qinhuangdao 066011, China)
出处
《塑性工程学报》
CAS
CSCD
北大核心
2018年第3期174-180,共7页
Journal of Plasticity Engineering
基金
河北省院士工作站建设专项资助(179A76193H)
