MORPHOLOGIES OF PRIMARY AL3FE IN BRIDGMAN SOLIDIFICATION AND TIG WELD TRAVERSING OF HYPEREUTECTIC AL-FE ALLOYS

This study indicates that the final morphology of primary Al3Fe in Bridgman solidification and TIG weld traversing of Al-Fe alloys is dependent on both the growth velocity and alloy concentration. With an increase in growth velocity, the morphology changes from clustered and microfaceted to being plate-like, finally becoming needle-like with or without a star-like transverse section. The initial morphology of plate-like primary Al3Fe is a needle-like dendritic form with a starlike transverse section behind the tip. A route for the formation of the plate-like primary Al3Fe from such needle-like dendrite tips is proposed.