International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

This paper investigates the effects of oil quenching and tempering at various temperatures on the mechanical and thermal properties of X155CrVMo12-1 tool steel. The steel specimens were austenitized at 1030 °C for half an hour, followed by quenching in oil and tempering at temperatures ranging from 50 °C to 700 °C. Mechanical properties were assessed by measuring the microhardness of the samples after each heat treatment. Thermal properties were investigated using the Xenon flash method (DXF analysis) to measure thermal diffusivity, thermal conductivity, and specific heat. The results show that the highest microhardness values were achieved after quenching,
while the lowest values were observed for thermal diffusivity and thermal conductivity. Following quenching, the microhardness values gradually decreased with an increase in tempering temperature, whereas the values of thermal diffusivity and thermal conductivity increased. Even after tempering at 500 °C, the microhardness values remained quite high, with only a 23.41% decrease from the quenched state. Furthermore, there was a significant improvement in thermal properties, with thermal diffusivity increasing by 38.34% and thermal conductivity improving by 23.99%.

Nickel aluminum bronze with the composition CuAl9Ni3Fe3 was investigated in this paper. After casting, the alloy was annealed at 900 °C followed by quenching. Thermodynamic calculation of the existing phases was performed using the ThermoCalc software. Quenched NAB samples were further aged for 1 h at 300 °C, 350 °C, and 400 °C. During the experiment, the values of hardness and microhardness were examined using standardized Vickers measurement methods. Microstructural analysis was performed using scanning electron microscopy equipped with an energy-dispersive spectrometer. During the precipitation hardening, β’ martensite eutectoidly decomposed into α and κ phases causing an increase in mechanical properties.

Cu-based shape memory alloys are increasingly used instead of nitinol alloys, due to their low price, good shape memory effect and superelasticity. In this work, Cu-Al-Mn alloys with different content of aluminium were investigated. Alloys were melted in the electric-arc furnace and casted in the cylindrical moulds as well as continuous casted. Microstructure of prepared samples was followed by scanning electron microscopy and phase transformations were determined by DSC analysis.