Re-formation of AlP compound in Al–Si melt

Three morphologies of AlP, i.e. block, flake and dendrite, have been found in Al–Cu–P master alloys fabricated under different conditions. When Al–Cu–P master alloy with flaky AlP is used to refine hypereutectic Al–Si alloy, the morphology of AlP particles located in the center of the primary silicon is significantly different from the flaky ones added through the master alloy; adding blocky AlP into the melt, differences also exist in the morphology of AlP with different fabrication parameters. It is manifested that the AlP substrates re-form from the melt after partial disassociation and dissolution of the previously added AlP particles, which is a necessary part of the refinement process of hypereutectic Al–Si alloys.