Research On Heat-resistant Performance Of Squeeze Casting Al-Cu Alloys With High Fe, Ni Content

Heat-resistant casting Al-Cu alloys have been widely applied in aerospace, military engine parts and automobile heat components, due to light weight, high strength and toughness, as well as good thermal conductivity. In recent years, the increasingly demanding legislation about exhaust emissions leads to a tendency that the efficiency of automotive engines is constantly rising, which has placed greater demands on the heat resistance property of aluminum alloys. Alloying is one of the most important and practical methods to improve the elevated-temperature mechanical properties of aluminum alloys. And advanced casting process improves the morphology and distribution of second phase which is beneficial for the heat resistance property of aluminum alloys. In this paper, the effect of Fe, Ni content and applied pressure on the microstructures, room and elevated temperature mechanical properties, creep resistance of the Al-5.0Cu-0.6Mn alloys have been studied. The main research contents and results are as follows:The effect of applied pressure on the microstructures, room and elevated temperature mechanical properties of Al-5.0Cu-0.6Mn-1.0Fe and Al-5.0Cu-0.6Mn-0.5Fe alloys with different Ni content has been studied. The applied pressure refines the grain size and secondary dendrite arm space of the alloys, improves the morphology and distribution of iron-rich phase& Ni-rich phase, and eliminates the porosity to obtain a dense uniform structure. The ultimate tensile strength, yield strength and microhardness of the alloys decrease with the increase of tensile temperature, while the elongation increases gradually. The applied pressure improves the ultimate tensile strength and yield strength at room temperature and 200℃ significantly. However, the increasment becomes unconspicuous with the increase of temperature. The applied pressure improve the microhardness and elongation obviously at various temperatures.We have studied the effect of Ni content on the microstructures, room and elevated temperature strength of the Al-Cu-Mn-1.0Fe and Al-Cu-Mn-0.5Fe alloys. With the increase of Ni content in Al-Cu-Mn-1.0Fe alloys, the amount of bulky harmful Al7Cu2 Fe phase decreases, and the amount of Al9 Fe Ni phase increase which is good for elevated temperature mechanical properties. When the content of Ni increases to 1.5%, the Al3 Cu Ni phase forms in the alloys which is better for the elevated temperature mechanical properties. At the same time, the size of Fe-rich & Ni-rich phase decreases, the distribution becomes more diffuse, the shape becomes more complex. The ultimate tensile strength and yield strength at various temperatures of Al-Cu-Mn-1.0Fe alloys increase with the increase of Ni content. With the increase of Ni content in Al-Cu-Mn-0.5Fe alloys, the amount of Fe-rich & Ni-rich phase iecreases, but no new phase formes, the size of Fe-rich & Ni-rich phase decreases slightly, but the distribution becomes nonuniform, which leads to second-phase strengthening weakened and casting properties deteriorated. The formation of Fe-rich & Ni-rich phase will consume the Cu dissolved in α matrix, which leads to solution strengthening and precipitation strengthening weakened. The ultimate tensile strength and yield strength at various temperatures of Al-Cu-Mn-0.5Fe alloys become lower with the increase of Ni content.The effect of Fe content on the room and elevated temperature strength of the alloys with the same Ni content and applied pressure has been studied. The increase of Fe content is detrimental to the room and elevated temperature strength of the alloys with low Ni content. But the increase of Fe content is conducive to the room and elevated temperature strength of the alloys with high Ni content.The effect of applied pressure on creep resistance of Al-Cu-Mn-1.0Fe-1.0Ni alloys has been investigated. The creep resistance of 75 MPa applied pressure alloy is better than 0MPa alloy significantly at various temperatures and applied stress. The creep mechanism of two kinds of alloys are all dislocation climb-controlled creep.