Effect of zirconium on structure and properties of high carbon Fe - 10.5 wt-%Al alloy

Abstract

The effects of zirconium additions on the structure and properties of high carbon Fe - 10.5 wt-%Al alloy have been investigated. Three different alloys with nominal compositions, Fe - 10.5Al - 0.7C (base), Fe - 10.5Al - 0.7C - 0.1Zr and Fe - 10.5Al - 0 7C - 0.17Zr were prepared. Processing of these alloys through a combination of air induction melting with flux cover (AIMFC) and electroslag remelting (ESR) yielded sound ingots free from gas and microporosity with very low levels of sulphur, oxygen, and nitrogen. This process route also resulted in excellent recovery of aluminium and zirconium. The ESR ingots were hot forged and hot rolled at 1375 K and the hot rolled alloys were examined using scanning electron microscopy, electronprobe microanalysis, and X-ray diffraction to understand the microstructure of these alloys. The ternary, Fe - 10.5Al - 0.7C (base) alloy exhibited a two phase microstructure consisting of a large volume fraction of Fe3AlC0.5 precipitates in an Fe - Al (α) matrix. Addition of zirconium (0.1 and 0.17%) resulted in the precipitation of a very small volume fraction of fine zirconium oxycarbide particles in the Fe - Al ( α ) matrix in addition to a large volume fraction of Fe3AlC0.5 precipitates. Tensile and creep rupture tests were performed on all three alloys in the hot rolled condition. The base Fe - 10.5Al - 0.7C alloy exhibited poor room temperature ductility and creep properties. Addition of 0.1%Zr to the base alloy resulted in significant improvement in room temperature and high temperature ductility and creep properties. However, further increase in Zr addition from 0.1 to 0.17% was not beneficial.