晶粒尺寸和膜厚度对介观尺度铝箔蠕变变形的影响

EFFECTS OF GRAIN SIZE AND THICKNESS ON CREEP DEFORMATION OF ALUMINIUM THIN FOILS WITH MESO-SCALE

通过在200℃恒载荷的高温变形实验,对厚度为10—350μm铝箔的等温塑性变形进行了研究.考察了铝箔厚度(t)和晶粒大小(d)对高温变形速率(ε)的影响规律,用T/d参量能很好的描述塑变的尺度效应.在t/d<1的变形样品中,TEM观察到晶界附近出现亚晶粒,证实其变形服从位错蠕变的幂率饥制.t/d对应变速率的影响归结勾晶粒内自由界面和晶界的面积比.给出了一个经验公式来描述应变速率和t/d的关系:ε=Aσ~n(t/d)^(1.95),其中应力指数n=n′-0.8151n(t/d),n′为相应块体材料的应力指数.

Constant stress creep experiments were carried out at 200 ℃ for aluminium thin foils with a thickness range of 10-350 μm. The effects of the thickness （t） and the grain size （d） on the strain rate （ε） were studied and the parameter, t/d, can better describe those effects. Subgrains were found near the grain boundary by TEM in the deformed specimen with t/d 〈 1, which confirmed that the deformation mechanism is dislocation power-law creep. An empirical formula, ε = Aσ^n（t/d）^1.95, n = n′-0.815ln（t/d）, n′ is the stress exponent of the block meterial, was obtained to describe the relation of t/d to ε, which basically depended on the ratio of grain boundary area to the free boundary area.