Squeeze casting and strengthening mechanism of high-strengthAl-Ni casting aluminum alloys

Abstract:

In order to develop new high-strength cast aluminum alloys, AlZn6Ni4Mg2Cu casting aluminum alloys based on Al-Ni eutectic system were prepared in sand casting process, permanent-mold casting process and squeeze casting process. The influence of Ni element, casting process and heat treatment on the microstructure and mechanical properties were studied. The result indicated, 4% (mass percent) of Ni formed a large number of eutectic structure (a-Al + Al3Ni) in the aluminum alloy, which improved their casting properties and mechanical properties, and had a role of eutectic strengthening. Heat treatment resulted in globalization of Al3Ni phases and aging precipitation of MgZn2 phases, which improved their strength. Compared with sand casting and permanent-mold casting, the grains and Al3Ni phases in squeeze casting process were finest, the mechanical propertis were best, the tensile strength of 586MPa, the elongation percent of 3.5%. The conclusion is that strengthening mechanism of AlZn6Ni4Mg2Cu casting aluminum alloy is aging strengthening of η(MgZn2) phases and dispersion strengthening of Al3Ni phases, mechanical properties reach the best value after squeeze casting and T6 heat treatment.

Key words:Al-Zn-Ni-Mg-Cu casting aluminum alloy; Al₃Ni phases; squeeze casting; eutectic strengthening