Thermal dimensional stability in fiber reinforced magnesium alloys

Abstract

The thermal dimensional stability of short alumina fiber reinforced magnesium alloys (FRMg) was examined with the following results. (1) In the case of the pure magnesium matrix FRMg, the thermal stress originating in the difference of the thermal expansion coefficients between the fiber and the matrix is effectively relaxed by the plastic deformation in the matrix upon quenching. As a result of the stress relaxation, the FRMg shows excellent dimensional stability during subsequent annealing. (2) In the case of Mg-Nd alloy matrix FRMg, a high residual tensile stress is induced in the matrix by quenching, because slip deformation is highly suppressed owing to the high flow stress level of the alloyed matrix. The FRMg undergoes creep elongation during subsequent annealing. (3) The thermal dimensional stability of the FRMg depends on the thermal stress and the amount of stress relaxation induced by slip deformation in the matrix. In order to obtain superior dimensional stability, it is important to select the system in which the difference in the thermal expansion coefficients between the fiber and matrix is small and in which the flow stress level of the matrix is low.

Keywords:

• fiber reinforced metal (magnesium alloy)
• thermal stress
• plastic deformation
• stress relaxation
• creep elongation