Effects of Al Content on Phase Transformation in FeV50 Alloy and Its Mechanism

FeV50 alloys with different Al contents were smelted and cooled to room temperature in the furnace,then their phases and microstructures were investigated by X-ray diffraction（XRD）and scanning electron microscope（SEM）respectively.The results showed that with the increase of Al content in FeV50,the phase transformation from σ phase to α phase was found.The 0.8% Al content was so critical that when it was below 0.8%,FeV50 was in form of σ phase,but when above 0.8%,two phases coexisted until a single α phase was obtained.It is supposed that Al affects the phase transformation in two ways.First,critical nucleus size becomes larger with the increase of Al which results in less energy available as driving force for α→σ phase transformation in the system.Second,the higher Al content,the stronger its inhibitory effect on the Fe atom diffusion,and as a result allotropic transformation of Fe is prevented,thus,α→σ phase transformation is retarded.