Fabrication of Fe-Mn-Si-Cr shape memory alloy fiber/aluminum matrix smart composite by casting

Abstract

If the composites are reinforced by the shape memory alloy (SMA) fiber that shrinks in the matrix, one can introduce an artificial compressive residual stress along the direction of the shrinkage. In our previous study, an SMA fiber/plaster smart composite, using Fe-Mn-Si-Cr alloy fibers, was fabricated and it was found that the bending strength of the composite was improved by the compressive stress due to the shape recovery force of the SMA fibers. However, the imperfect bonding at interface between SMA fiber and plaster matrix decreased the bending strength of fabricated composite. In this study, Al matrix smart composites containing Fe-Mn-Si-Cr SMA fibers are studied, since it is well known that Fe and its alloys react with Al. Straight Fe-28.2mass%Mn-6.03mass%Si-5.11mass%Cr SMA fibers were arranged on the fiber holder, they were immersed into a mold with molten Al. During this step, ferrous SMA reacted with Al at fiber/matrix interface, results in the good bonding strength at interface. After solidification, ferrous SMA fiber/Al matrix composite could be obtained. This composite was subjected to the rolling deformation to induce the martensitic transformation from γ austenite to ϵ martensite in SMA fibers. Then the composite was heated to induce the reverse transformation from ϵ martensite to γ austenite. The ferrous SMA fibers in the composite shrank during this reverse transformation, which could induce tensile stress in fibers and compressive stress in the matrix. This compressive stress in the matrix is a key factor that enhances the mechanical properties of such smart composite. Mechanical properties of fabricated smart composites were also studied.