Investigation of the influence of thermo-mechanical treatments on the structural-phase state and mechanical properties of VZH171 alloy

The analysis of the influence of thermo-mechanical treatment (TMT) (rolling on the degree of deformation of 50%, annealing at temperatures of 600-1200 °C, 1 h) on the microstructure and phase composition of the alloy VZH171 in the initial non-nitrided state and after bulk nitriding. It was shown that nitriding leads to an increase in the thermal stability of the alloy microstructure. If the primary recrystallization and formation of fine-grained structure in the non-nitrided alloy begins to take place intensively at a temperature above 1000 ° C, then in the nitrided alloy, even at an annealing temperature of 1200 °C, the process of collective recrystallization does not receive significant development, the microstructure remains ultra-fine - grained (grain size 5-10 mm). Mechanical properties of nitrided and non-nitrided alloy were investigated. It was found that nitriding does not significantly affect the strength of the alloy at room temperature. When tested at 800 ° C maximum strength and minimum ductility demonstrates nitrided alloy after rolling and subsequent annealing 600 ° C. The optimal ratio of tensile strength (480 MPa) and ductility (elongation to fracture value of 23%) is observed in the nitrided alloy after TMT and annealing at 800 °C.

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