Hereditary Effect of the Structure of the Charge on Density, Gas Content, and Processes of Solidification of an Al-Si-Cu Alloy System

摘要

The effect of the structure of the initial charge density in liquid and solid states, as well as on the temperature-time parameters of the process of solidification of the AK6M2 alloy (A1-6% Si-2% Cu), is shown. To obtain a coarse-crystal charge (C charge), part of the melt is crystallized in ceramic forms in a sand backfill with a cooling rate of similar to 0.5-1.0 degrees C/s. The fine-crystal charge (F charge) in the form of thin ingots weighing 0.2-0.3 kg is obtained by crystallization of the melt in cast-iron cold molds with similar to 5.0-10 degrees C/s. Further, the charge billets are separately melted, re-refined and degassed, and the samples are poured to determine the gas content and density in the liquid (d(L)) and solid (d(S)) states. It is established that structural information from the original charge of the alloy is stable in the solid-liquid-solid system. Direct thermal analysis is used to find that the melt obtained from the F charge hardens at low temperatures: the decrease in liquidus temperature t(L) is 3 degrees C; the temperature of the beginning of solidification of the eutectic is reduced by 10 degrees C, and the temperature of the end of solidification of a eutectic is 3 degrees C in comparison with the melt of the C charge. At the same time, the formation of alpha-Al and eutectic dendrites in the melt from the F charge occurs 0.4 and 0.6 min more quickly, respectively. The results obtained on the Paraboloid-4 installation show that a smaller number of pulses throughout the studied temperature range passes through the melt from the F charge, which confirms its increased density when compared to the alloy from the C charge. Thus, for the melt from the F charge, the values of the degrees of compaction were -Delta J(1)similar to 278.66 and -Delta J(e) similar to 129.83 imp/s and, for the melt from the C charge, -Delta J(1) similar to 302.9 and -Delta J(e) similar to 163.47 imp/s. The values of the phase-transition temperatures determined by anomalies on the temperature dependence Jt practically coincide with the results of direct thermal analysis. The main technological recommendations of management by structural information in aluminum alloys are formulated from the position of the phenomenon of structural heredity.