Effect of Aluminum Content on Microstructure of HK40 Alloy

The effects of aluminum content on the microstructure of HK40 alloy were studied by optical microscope.The distribution of elements in matrix was analyzed by electron probe microanalysis(EPMA-1600).The phases were confirmed by X-ray diffraction.The results show that Al element are all dissolved in the matrix of HK40 alloy when Al concent is below 2wt%Al,and no precipitates form.The microstructure of the alloy is austenite+carbide,which is the same as HK40 alloy.When Al concent is 4wt% or higher,a lot of AlNi,Fe2Al5 dendrite phase appear in the alloy and the matrix is γ-Fe solution.When aluminum content in steel increase to 6wt%,the matrix of the alloy transforms into α-Fe based,and a large number of AlNi metallic compounds exists in the matrix.