The Investigation of Mechanical and Functional Properties and Microstructural Features of Coarse-Grained SME Ti49.0Ni51.0 Alloy during Multiple Martensitic Transformations and Annealing

Abstract

The paper was investigated the effect of preliminary multiple martensitic transformations on the microstructure and mechanical and functional stability during subsequent annealing in the range of aging temperatures of the Ti49.051.0 alloy in the coarse-grained state. The structure in the initial state has an austenitic structure with a grain size of 30 ± 5 μm; after TC, the structure is martensite with a grain size of 30 ± 5 μm. According to the results of mechanical tensile tests, thermal cycling leads to an increase in the yield stress, which is associated with the generation and accumulation of dislocations. An increase in the number of cycles to n = 100 led to a slight decrease in the yield stress, which may be due to the saturation effect during thermal cycling. Subsequent aging at T=400 °C after thermal cycling showed that the yield stress increases. At the same time, the results of mechanical tests showed that, in general, the preliminary TC (n = 100) with subsequent aging contributes to an increase in the yield strength and strength. The structure revealed after thermal cycling and subsequent low-temperature annealing confirms the precipitation of aging strengthening particles Ti3Ni4.