Effects Of Zr On Solidification Behavior And Heat-treated Microstructure Of Al-3Fe Alloy

Al-Fe alloys have low density,high thermostability,rich in material and low price,which have high potential in the aerospace,weapons and automotive fields.However,large plate-like Al3Fe phase will be produced during normal solidification process,which splits Al matrix and severely reduces the mechanical property of the alloy.This limits the application of Al-Fe alloys.In order to optimize the microstructure of Al-Fe alloy,this paper investigates the solidification microstructure of Al-3Fe alloy solidified under crucible with insulation measures and iron mold with different mold temperature.The changes of microstructure and hardness of Al-3Fe alloys by iron mold casting with different Zr content were studied.Precipitation characteristics of Fe-rich phase and Zrcontaining phase under different aging conditions of Al-3Fe alloy with different Zr content were also investigated.The main conclusions are as follows:(1)The solidification microstructure of Al-3Fe alloy by slow cooling is primary Al3Fe+Al-Al6Fe eutectic.The solidification microstructure of Al-3Fe alloy by iron mold casting is Al-Al6Fe eutectic.With the increase of the mold temperature,the microstructures of the central parts of ingots have regular changes are as follows:transgranular structure,dendritic ?-Al,dendritic and cell ?-Al,equiaxed eutectic cell.(2)Branches of Al3Fe phase of Al-3Fe alloy are reduced with Zr addition by slow cooling.The morphology of Al3Fe changed from long needle to plate-like.Al-Al6Fe eutectic cells are refined with Zr addition by iron mold casting.However,plate-like Al3Fe formed in cell boundaries with Zr addition.Hardness of refinement cells is not obviously improved.(3)Al6Fe fibres begin to spheroidize during aging at 450?.When the aging temperature is 500?,spheroidization of A16Fe is more obvious.Moreover,rod-like Al3Fe formed in cell boundaries at the same aging condition.Zr addition can stabilize the Al6Fe fibres' morphology.Metastable Al3Zr(L12)particles precipitate in Al matrix finely with 0.2%Zr addition during aging at 450? for 10h.The hardness of alloy is improved obviously.Increasing the aging temperature to 500?,metastable Al3Zr(L12)particles have dissolved and some plate-like Zr-containing phases and needle-like Al3Fe phases have precipitated.The hardness of the alloy is decreased because of the change of microstructure.