Analysis of eccentric unbonded bimetal rod in ECAP based on different arrangements of soft and hard metals

In this paper, an analytical model of ECAP process with an eccentric unbonded bimetal rod is proposed by slab method. Based on the discussion, the effects of the eccentricity ratio and the diameter of inner rod as well as the geometrical parameters of the mold on the bonding process are obtained. Also this is the first time that different material arrangements are both taken into the consideration in ECAP. Two kinds of eccentric bimetal rods are researched, when outer pipe is hard and inner core rod is soft, the eccentricity ratio will be relieved. When the outer is soft and inner is hard, the eccentricity ratio will be enlarged. These changes can be more than 10% in some situations. In order to verify these conclusions, some experiments with aluminum and copper are designed and conducted. In these experiments, 3 different molds and 10 different eccentricity ratios as well as 5 different inner diameters are discussed with two kinds of eccentric bimetal rods in ECAP. The measured results are in agreement with those calculated by analytical model. Most of the errors between the measurements and calculations are less than 6%.