Research results of novel composite materials with low hysteresis during heating and cooling for pistons of combustion engines

Research results of novel silumins on pistons for combustion engines, which have high mechanical properties within the range of piston higher operating temperatures, 100-300°C, are presented in the paper. Silumins contain enlarging concentration of the nickel and copper alloy additives up to 4.0, and chrome and molybdenum alloy additives up to 1.0%. Occurrence of given microstructure in piston-silumins results in almost the same values of the coefficient thermal expansion during the heating up to the 300 °C temperature and during the next cooling into the ambient temperature. Small values of the coefficient of expansion of thermal and small differences between values of the coefficient of thermal expansion during heating and cooling enable on application of small values of working clearances between piston and the cylinder liner. As a consequence they make possible, the low exhaust emission level, and the low noise level. The pistons from alloys with small values ofthe coefficient of thermal expansion, small differences of this coefficient during heating and cooling are novel aspects presented in paper. Research results of strength and metallographic parameters, research results of the coefficient of thermal expansion, comparative engine research results are represented in the paper. In particular representative chemical components for a standard alloy and novel alloy, mechanical properties investigated alloys after solution heat treatment, wear resistance of novel alloy compared with two cast irons, ATD curves, fibrous construction, silicon construction, microstructure of novel alloy, courses of changes of the coefficient of thermal expansion in the function of the temperature during heating and cooling are presented in the paper.