Microstructure characterization and mechanical properties of the 304SS-(NiTif/FeAl) metal-intermetallic laminate composites

Abstract

In this work, a novel continuous NiTi Shape Memory Alloy Fiber Reinforced (SMAFR) B2-FeAl based metal-intermetallic laminate (MIL) composite was prepared via two-step vacuum hot pressing combined with “multi-thin foils” stacking configuration. The microstructure characterization of the composite was conducted by using X-ray diffractometer, scanning electron microscopy, electron backscattered diffraction and transmission electron microscopy. The compressive and tensile properties of the composites were measured. Results indicated that the SMAFR MIL composite exhibits multi-layer structure consisting of residual stainless steel layer, newly-formed intermetallic layer and intermediate transition layer. The intermetallic layer is composed of several sublayers with the boundaries of centerlines, and B2-FeAl phase is the main phase in this layer. NiTi fibers locate at the centerlines in the intermetallic layer and show a uniform distribution. A metallurgical interfacial bonding between NiTi fiber and FeAl matrix was obtained through the inter-diffusion of Ni, Ti and Al elements across the interface. In the intermediate transition layer, B2 phase was also the dominant phase, and a large amount of fine Al-rich precipitates dispersed in the matrix. Compared with the MIL composite without NiTi fibers, the SMAFR MIL composite possesses superior compressive and tensile properties, which are mainly attributed to (Ⅰ) high tensile properties of NiTi fiber, (Ⅱ) a good interfacial bonding of NiTi/B2-FeAl, (Ⅲ) strong interfacial reaction products, and (Ⅳ) pullout effect of NiTi fibers.