Investigation of the kinetics of physical and mechanical properties of hardened samples made of B95 and D16T alloys due time-temperature expositions and multicycle fatigue tests

The kinetics of residual stresses and physical and mechanical properties of the hardened air shot-blasting layer of smooth specimens and specimens with semicircular cuts of aluminum D16T and B95 alloys as a result of time-temperature expositions and multicycle fatigue tests is investigated. This research was done for symmetric loading cycle in terms of bending and tension-compression tests and the base of $10^7$ cycles. The growth of increment of the endurance limit of hardened parts with stress concentrators in comparison with non-reinforced specimens is established experimentally and by calculation. It is shown that the time-temperature exposition causes the relaxation of residual stresses and the reduction of increment of the endurance limit. In fact, surface plastic hardening significantly affects the growth of microhardness in comparison with samples unhardened. Microhardness decreases to values corresponding to unhardened sample after time-temperature expositions. The surface hardening increases the roughness layer and further time-temperature exposition and fatigue tests have no effect on these parameters. There is agreement between the calculated and experimental data.