| Aluminum alloy with high specific stiffness and strength, wear resistance, excellent high temperature performance, etc., have broad prospects in the piston industry applications.In order to ensure the variety of phases of Al-Si-Cu-Mg-Ni system alloy and the phase’s solidification order of model alloys. Model alloys Al-13Si, Al-13Si-4Cu, Al-13Si-4Cu-2Ni and Al-13Si-4Cu-1Mg-2Ni were prepared.In order to obtain precipitation sequences of phases, Al-13Si-4Cu-Mg-2Ni alloy liquid quenching at different temperatures.In order to study piston alloy precipitates phases and the effect of Cu element on precipitation order of phases, the solidification precipitation process of Al-Si-Cu-Mg-Ni system piston alloy were analyzed. Five kinds of Al-Si-Cu-Mg-Ni system model alloys Al-13Si-1Mg-2Ni-xCu (x= 0,2,3,4,5 mass fraction) were prepared. The effects of Cu contents on the composition and shape of liquid precipitation phase were studied by optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD). The evolution order of the liquid precipitation phase of model alloys was analyzed.In order to study the effect of different cooling rates on Al-Si-Cu-Mg-Ni system alloy piston.Three kinds of different cooling rates alloy (0.11 ℃·s-、0.29℃·s-1、14.93 ℃·s-1) were prepared, it was Prepared by water-cooled metal mold, metal mold and sand.The influence of different cooling rates on phase composition and mechanical properties.The experimental results show:in Al-13Si-4Cu-1Mg-2Ni model alloy, the main phase include Q-Al5Cu2Mg8Si6,θ-Al2Cu,ε-Al3Ni,γ-Al7Cu4Ni and 8-Al3CuNi. At the low ratio of Cu and Ni, phase formed as ε-Al3Ni, conversely generate 8 phase and γ-phase, two phases depending on the proportion of the required size of Cu, Ni content is determined. As the cooling rate increase (0.11-14.93℃·s-1), the grain size is reduced from 81.4μm to 30.4 μm, the ε-Al3Ni phase disappears, and the Q-Al5Cu2Mg8Si6 phase emerges. The white 8-phase and y-phase like reticular and cluster, its size decreases and change to Chinese characters type.The mechanical properties of cast ingot improved significantly, the hardness was increasing from 80.9 HB of 0.11 ℃·s-1 to 125.7 HB of 14.93 ℃·s-1. Tensile Strength was increasing from 189.3 MPa to 282.5 MPa. Elongation after fracture is increased from 1.6% to 2.8%. To Al-13Si-1Mg-2Ni-xCu alloys, the predominant strengthening phase was ε-Al3Ni and a small amount of M-Mg2Si phase in Al-Si system piston alloy without Cu content. The δ-Al3CuNi phase formed in the alloy with 2%Cu content (mass fraction), and grew around the ε-Al3Ni phase. Its quantity showed a increasing trend. When the Cu content exceeds 3%, the quantity of δ-Al3CuNi phase decreased, whereas that of γ-Al7Cu4Ni increased. The lump shape γ-Al7Cu4Ni phase formed near the δ-Al3CuNi phase, and ε-Al3Ni phase disappeared. When Cu content increased to 4%(mass fraction), Q-Al5Cu2Mg8Si6 phase appeared near δ-Al3CuNi phase or γ-Al7Cu4Ni phase. The eutectic microstructure contains Q-Al5Cu2Mg8Si6 phase and γ-Al7Cu4Ni phase in the alloy with 5% Cu content. |
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