Intermetallic phase evolution and strengthening effect in Al-Mg2Si alloys with different Cu/Ni ratios
Microalloying of an Al–15%Mg2Si alloy (wt%) with Ni and Cu produced an enhanced strengthening response, increasing hardness whilst also improving tensile strength due to the formation and evolution of intermetallic phases. With the increase of Cu/Ni ratios, intermetallic phases translate from Al3Ni or Al3CuNi to Al7Cu4Ni, and the total volume fraction of Al3CuNi and Al7Cu4Ni increases to 3.51% (1%Ni and 5%Cu, Cu/Ni ratio = 5). The thermally stable Al3CuNi and Al7Cu4Ni phases are connected to each other forming chains and tend to build up a network. As a result, the ultimate tensile strength (at 350 °C) of the alloy (Cu/Ni ratio = 5) reached up to 132 MPa, 131.6% higher than that of Al–15%Mg2Si alloy.