Al–Mg–Si系合金の曲げ加工性に及ぼす時効析出物の影響

Abstract

Al–Mg–Si alloys are usually applied a T4 temper as the plate material for automobile bodies, because of necessity of a high bake hardening property. Many reports about the improvement in the bendability of Al–Mg–Si alloys applied a T4 temper has been published, because they easily crack during the hemming process. On the other hand, Al–Mg–Si alloys applied T6 and T7 tempers are used for the material of wiring plates and heat radiation devices. A high electrical conductivity and good bendability are necessary for these devices. In this paper, the effect of the aging conditions on the bendability was investigated. As a result, the bendability at the T6 temper significantly decreased. The bendability under the aging temper, and over the aging temper was better than that at the T6 temper. Specimens treated by natural-aging at high temperature before the T6 temper easily cracked during the bending test. It was postulated that the formation of shear bands was significant and the bendability decreased during the bending test under the high density and finely β″ phase precipitate conditions.