Synthesis and mechanical properties of open-cell Ni–Fe–Cr foams

Reticulated Ni–45Fe foams were alloyed with chromium by pack-chromizing, resulting in Ni–Fe–Cr foams with 35.7–37 wt.%Fe, 13.8–25.7 wt.%Cr. The Ni–45Fe foam was used as a substrate, whose struts were composed of Ni–Fe–Ni sandwich layers. The thickness and composition of the Ni–Fe–Cr foam struts were controlled by varying the deposition time. The mechanical properties of the Ni–Fe–(13.8–25.7) Cr foams were compared to the Ni and Ni–45Fe foams at ambient temperature. Scanning electron microscopy (SEM), optical micrographs (OM) and energy dispersive spectrum (EDS) analysis were used to investigate the microstructures and the elemental composition profiles of the Ni–Fe–Cr foams respectively. The X-ray diffraction technique was used for phase identification of the foam materials. The results show that the Cr coating is dense and well adhered to the Ni–45Fe substrate. The Ni–Fe–Cr foams after homogenization exhibit a fine equiaxed grain structure. Despite an increase in density compared with the Ni–45Fe foams, the Ni–Fe–Cr foams after homogenization exhibit enhancements in both absolute and specific strength, as well as in energy absorption.