The study presents the technological backgrounds of the process of melting and casting Al-Co, Al-Ni, and Al-Ti master alloys, used as refiners of the microstructure of cast silumins. Basing on the analysis of phase equilibrium diagrams for an Al-Me (Co, Ni, Ti) system at a temperature of 900oC, the characteristic intermetallic phases of AlxMey were investigated. Due to their similarity with Al and Si in respect of both structure and lattice arrangement, these phases may act as heterogeneous nuclei and promote solution hardening during, e.g., heat treatment. Using the method of thermal analysis ATD, the temperature was plotted in function of time, and then the characteristic values of the solidification parameters of master alloys were read out from the respective curves.
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The investigations of phase transformations described in this study were carried out on hypoeutectic alloys from the Al-Si during heating and cooling. The determination and analysis of characteristic temperature values from the solidification range was made by the DSC method in calorimetric investigations carried out on a high-temperature multi HTC Setaram scanning calorimeter. Applying the lever rule, the phase composition of the examined slumins was calculated and compared with the results of DSC calorimetry.
Wyznaczono wartości entalpii topnienia i krzepnięcia oraz temperatury krystalizacji składników fazowych stopów Al-Si. Przeprowadzono badania metodą analizy termicznej ATD oraz analizy kalorymetrycznej DSC, na podstawie których określono efekty endotermiczne podczas topnienia i egzotermiczne podczas krzepnięcia badanych siluminów. Opierając się na układzie równowagi fazowej oraz wykorzystując wyniki skaningowej analizy kalorymetrycznej, obliczono skład fazowy (udział eutektyki i dendrytów aluminium). Na tej podstawie stwierdzono zależność między składem fazowym badanych stopów a występującą segregacją krzemu w roztworze.
EN
Enthalpy of melting, solidification process and melting points were determined for phase compounds of Al-Si alloys. DTA Thermal analysis and DSC calorimetric analysis were carried out. Endothermic and exothermic effects of researched alloys were determined during solidification and melting process. Phase composition were calculated with using phase diagram as well as results of calorimetric analysis (share of eutectic and silicon dendrites). In analyzed alloys relationship between phase composition and segregation of silicon were observed.
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The investigations of phase transformations described in this study were carried out on hypoeutectic alloys from the Al-Si system (AlSi3, AlSi6 and AlSi9) during heating and cooling. The determination and analysis of characteristic temperature values from the solidification range was made by the DSC method in calorimetric investigations carried out on a high-temperature multi HTC scanning calorimeter. Applying the lever rule, the phase composition of the examined silumins was calculated and compared with the results of DSC calorimetry, obtaining a good correlation of the results.
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The study was related with determination of the values of enthalpy of melting and solidification of hypereutectic AlSi18, AlSi21 and AlSi24 silumins modified with phosphorus in the form of Cu-P. The calorimetry, preceded by thermal analysis and derivative thermal analysis (TA and DTA, respectively) was carried out on a high-temperature scanning calorimeter, model MHTC-96, made by SETARAM, applying the method of direct determination of parameters of the high-temperature process, and in particular of the enthalpy of phase transformations. Modern control and measuring instruments coupled with PC computer provide a very precise tool for determination of these transformations. An additional advantage was development of appropriate software called "SETSOFT", owing to which it was possible to determine in an easy way the enthalpy of the investigated phase transformations. Moreover, an additional thermal effect, related most probably with pre-eutectic crystallization of primary silicon, was observed and confirmed by calorimetric examinations.