Dissolution Process Of Cu-P Allloy In Aluminum Melt

Aiming at the problem that the size of AlP particles is not easy to control as the primary nucleation silicon nucleation substrate.This paper took Cu-P master alloy as the research object,and used ZEISS Axio vert.A1 optical metallography microscope,scanning electron microscope?SEM?and D/MAX-2500 X-ray diffraction analyzer to analyze the solidification structure obtained by water quenching during static dissolution,and the dissolution process of Cu-P alloy in aluminum melt was studied systematically.It is found that the Cu-P alloy which is near the solid/liquid interface becomes single phase Cu₃P during the dissolution of the solid Cu-P alloy into the aluminum melt;the mixed solid layer of Al-Cu intermetallic compound and AlP is formed after the liquid Cu-P alloy is contacted with the aluminum melt.It is revealed that the dissolution process of solid Cu-P alloy in aluminum melt is as follows: The ?Cu phase in the surface of solid Cu-P alloy and its surrounding eutectic structure dissolves preferentially,which results in a small amount of eutectic Cu₃P and primary Cu₃P falling off.At the same time,the Cu-P alloy near the solid-liquid interface completely becomes a single phase Cu₃P and then enters a state where the single phase Cu₃P is dissolved into the aluminum solution.The solution process of the liquid Cu-P alloy into the aluminum melt is revealed as follows: After the liquid Cu-P alloy is contacted with the aluminum melt,a solid-phase mixed layer of AlP and Al-Cu intermetallic compound is formed,and then the whole solid-phase mixed layer moves into the liquid of Cu-P alloy.At the same time,phosphorus atoms and aluminum atoms continue to react to form AlP,and finally?Al-Cu?-AlP liquid-solid mixture is formed.It is found that the dissolution rate of Cu-P alloy in aluminum melt changes quickly first and then slowly.It is known from the experiments that the maximum dissolution rate of solid Cu-P alloy in aluminum melt was 0.84 g/min at 973 K,while the maximum dissolution rate of liquid Cu-P alloy is 20.78 g/min at 1073 K.The key to control the dissolution rate of Cu-P alloy in aluminum melt is found.During the dissolution process of solid Cu-P alloy in aluminum melt,the formed solid AlP and the formation of Cu-P alloy near the solid-liquid interface into single phase Cu₃P are the root causes of slow dissolution rate.During the dissolution process of liquid Cu-P alloy in aluminum melt,the formation of a solid-phase mixed layer of AlP and Al-Cu intermetallic compound is the key to control the dissolution rate.