Ｃａ添加Ｍｇ合金の制御圧延技術の開発

Abstract

In general, SF6 gas is widely used in order to protect the molten magnesium against oxidation. But SF6 gas is a typical green house gas being the source of global warming, so that the usage will be prohibited in near future. Ca is known to be effective for improving the oxidation resistance for magnesium alloy melts. However, it was reported that the addition of Ca would be resulted in the degradation of hot workability and mechanical properties. It is effective for the improvement of mechanical properties and formability to control the microstructure by controlled rolling process. The purpose of this study is the establishment of the technologies for controlled rolling process in Ca added magnesium alloys using isothermal rolling machine for suppression of edge cracks. In this study, the hot workability, recrystallization behavior and tensile properties after rolling of AZ61-xCa (x = 0∼0.45 mass%) was investigated. The results are as follows: 1.The addition of Ca was resulted in the significant degradation of hot workability because of the Al2Ca phase. The Al2Ca phase remained even after solution treatment at 698 K for 24 hr. 2.The recrystallization progression and grain growth rate of AZX610 alloys are obviously slower than that of steel. So multi-pass rolling with low reduction process can be effective to obtain fine microstructure without edge cracks. 3.Better in-plane isoropic ductility was obtained by texture control in controlled rolled AZX610 at 673 K compared with that of 573 K.