Наследственное влияние структуры шихты на плотность, газосодержание и процессы затвердевания сплава системы Al-Si-Cu

The paper provides the results obtained when studying the initial charge structure effect on the density, gas content and temperature-time parameters of AK6M2 (Al-6%Si-2%Cu) alloy solidification. Coarse crystalline charge billets ( C -charge) were obtained when pouring the melt into ceramic molds with sand filling providing a cooling rate υ охл ~0.5÷ 1.0 °C/s. Finely crystalline charge billets ( F -charge) were prepared by pouring the melt to cold cast iron molds ( υ охл ~ 5÷ 10 °C/s). Charge billets obtained were separately remelted with the same temperature-time conditions, rerefined and degassed with samples taken to determine hydrogen content as well as density values in liquid and solid states. It is established that structural information inherited from the initial charge billets is stable in the solid-liquid-solid system. It was found using direct thermal analysis that the melt obtained from C -charge solidifies with a reduction in liquidus temperature by 3 °С and in the temperatures of the beginning and end of eutectic solidification by 10 °C and 3 °С, respectively, as compared to the melt obtained from C -charge. At the same time, α-Al and eutectic dendrites form in the C -charge melt 0.4 and 0.6 min faster, respectively. The results obtained at the Paraboloid-4 unit showed that the F -charge melt has higher density as compared to the C -charge alloy due to a smaller number of pulses passing through it in the studied temperature range of 750 — 450 °C. Temperature values of aluminum and eutectic dendrite formation determined by J—t temperature relationships (where J is the number of γ pulses, t is the temperature) correlate with the results of direct thermal analysis. General practical recommendations on the purposeful conservation of positive structural information in aluminum alloys are formulated in terms of the structural heredity phenomenon.