Thermodynamic analysis of nanostructured (Fe,Cr)₃Al formation during mechanical alloying

Abstract

Nanostructured (Fe,Cr)₃Al compound was produced by mechanical alloying (MA) of the Fe₅₀Cr₂₅Al₂₅ elemental powder mixture, and the effect of Cr addition on the formation of solid solution in the ternary Fe–Cr–Al system was investigated. The structural and phase changes of powder particles during MA were studied using X-ray diffractometry and transmission electron microscopy. The results showed that at early stages of MA, a BCC-Fe(Cr,Al) solid solution was formed, which transformed to the disordered (Fe,Cr)₃Al compound by further milling. The thermodynamic analysis based on Miedema model showed that for all binary Fe–Al, Fe–Cr and Cr–Al systems and ternary Fe–Cr–Al system, the formation of solid solution is thermodynamically favourable for all compositions. It was also demonstrated that for the ternary Fe₅₀Cr₂₅Al₂₅ alloy, more driving force is available to form solid solution compared with the Fe₇₅Al₂₅ binary alloy. The results of thermodynamic analysis were in agreement with the MA results.

Keywords:

• Iron aluminides
• Mechanical alloying
• Miedema model
• Nanostructured materials