Effect of Plastic Deformation in Various Temperature-Rate Conditions on Structure and Mechanical Properties of Biodegradable Fe–30Mn–5Si Alloy

Rheological models of deformation behavior and structure formation of biodegradable Fe–30Mn–5Si shape memory alloy (wt pct) under various upsetting conditions from 250 °C to 900 °C with strain rates of 0.1, 1, and 10 s⁻¹ are studied. The relationship between the structure formation and the shape of compression stress–strain diagrams has been established. The main parameters of compression stress–strain diagrams, such as maximum stress (σ_max), apparent yield stress (σ_0,2), and maximum strain (e_max) achieved at σ_max are determined. The Vickers hardness was also measured. These parameters were found to be depending on the deformation temperature at a greater extent and, at a lesser extent, on the strain rate. According to optical and electron microscopy, the Fe–30Mn–5Si alloy exhibits high resistance to dynamic recrystallization process up to 900 °C. It has been shown by X-ray diffraction that the Fe–30Mn–5Si alloy is in a single-phase state (γ-austenite) in the temperature range from 250 °C to 700 °C. An increase in the deformation temperature leads to the appearance of a ε-martensite phase at room temperature. Based on the obtained results, favorable modes of subsequent thermomechanical treatment have been developed. These modes make it possible to obtain semi-products with high functional properties from the Fe–30Mn–Si alloy.