Ｍｇ‐Ａｌ系合金の減衰能に及ぼす合金元素量および熱処理の影響

Abstract

Magnesium alloys are well known to have high damping capacity. However, reports on damping characteristics of magnesium alloys, especially used practically, are very limited. In this study, the effects of alloy composition and heat treatment were investigated on the damping capacity of the hot-rolled and die-cast specimens of Mg–Al alloys. In addition, stress and frequency dependencies of the damping characteristics were also evaluated. The factors, which may influence the internal friction at the low stress range in magnesium alloys, were also investigated based on the Granato-Lücke theory. The increase in maximum bending stress applied to the specimen increases the specific damping capacity. This increment at low stress range is due to the internal friction of dislocation type mechanism in magnesium alloys. It is also found that the internal friction at high stress range does not agree with the Granato-Lücke theory. Therefore, besides dislocation type mechanism, there is a possibility of additional mechanism, for example, the formation of deformation twin in these alloys. Furthermore, increases in the contents of alloying elements remarkably decrease the specific damping capacity. However, the frequency does not affect the specific damping capacity.