A high-pressure torsion (HPT) with a number of revolutions (n) of up to 10 and an advanced method of accumulative HPT (AccHPT), n = 10 with subsequent post-deformation annealing (PDA) at 500 and 600 °C, were applied to a biodegradable Fe-30Mn-5Si (wt.%) alloy. The effect of HPT, AccHPT and AccHPT with PDA on the microstructure, phase composition, microhardness and electrochemical behavior in Hanks’ solution was studied. HPT with n = 1 and 5 resulted in forming a mixed submicrocrystalline (SMCS) and nanocrystalline (NCS)structure, while HPT, n = 10 and AccHPT, n = 10 resulted in a predominant NCS with grain/subgrain sizes of 15–100 nm and 5–40 nm, respectively. PDA after AccHPT resulted in a mixture of SMCS and NCS. HPT, n = 5, n = 10 and AccHPT, n = 10 led to a transition from a two-phase (γ-austenite and ε-martensite) state after reference quenching, and HPT, n = 1 to a single-phase state (stress-induced and deformed ε-martensite), while the AccHPT, n = 10 with PDA results in a two-phase state of γ-austenite and cooling-induced ε-martensite, similarly to reference heat treatment (RHT). The increase in n resulted in the microhardness increasing up to its maximum after AccHPT, followed by a slight decrease after PDA. HPT and AccHPT led the biodegradation rate to decrease as compared to the initial state. PDA after AccHPT at 500 and 600 °C resulted in a two-phase state corresponding to an elevated biodegradation rate without significant material softening. The observed electrochemical behavior features are explained by changes in a combination of the phase state and the overall level of crystal lattice distortion.

Fe-30Mn-5Si alloy subjected to a compression test at various deformation temperatures ranging from 350 to 900 °C with a strain rate of 1 s⁻¹ are studied. It was found that the Fe-30Mn-5Si alloy exhibits high resistance to the dynamic recrystallization process in a whole studied range of deformation temperatures. There are no differences in structure formation in the zone of action of tangential tensile stresses and peripheral and central zones of localized compressive stresses. The room-temperature X-ray diffraction study shows the presence of a single-phase state (FCC γ-austenite) after deformation temperature range from 350 to 700 °C and a two-phase state (FCC γ-austenite + HCP ε-martensite) after deformation test at 900 °C. The presence of a two-phase state provides a higher rate of biodegradation compared with a single-phase state. The changes in the biodegradation rate dependence on the structure change with an increase in the deformation temperature are explained. Favorable temperature regimes for subsequent thermomechanical processing are proposed based on the relationship between structure formation and biodegradation rate to obtain semi-products from the Fe-30Mn-5Si alloy.

Biomedical Ti-22Nb-6Zr, Ti-18Zr-15Nb, and Ti-41Zr-12Nb (at.%) shape memory alloys were subjected to cold rolling (CR) and subsequent post-deformation annealing (PDA). The evolutions of phase and structure states, crystallographic texture, and crystallographic limit of recovery strain were studied using EBSD, TEM, and XRD analyses. The study found that CR (e = 1.5) and PDA at 800 °C for 30 min results in fine- and coarse-grained structures. Severe CR (e = 3.0) and PDA at 550 °C for 5 min results in a recrystallized, equiaxed, predominantly ultrafine-grained structure of the β-phase with a small amount of low-angle boundaries. Increasing the degree of CR from moderate (e = 0.3) to severe (e = 3.0) results in a favorable strong {111}_ββ recrystallization texture. Alloys with low Zr content are more susceptible to this type of crystallographic texture formation during TMT, primarily due to a higher Nb content. The Ti-41Zr-12Nb alloy shows the highest crystallographic limit of recovery strain (ε_r^max ≈ 6%). The limit decreases to ≈5% (for Ti-18Zr-15Nb) and ≈3% (for Ti-22Nb-6Zr) when transitioning from high- to low-Zr alloys. The transition of Ti-Zr-Nb alloys from coarse-grained to ultrafine-grained structures of the β-phase and a decrease in grain size do not affect the crystallographic limit of recovery strain in the studied grain size ranges.

Рентгенографически изучено влияние режимов нагрева и охлаждения перед старением сплава Ti–22Nb–6Zr (ат.%) с памятью формы на интенсивность образования изотермической ω_iso-фазы в интервале температур от 250 до 350 °С в течение 1 и 3 ч. Показано, что для интенсивного образования ω_iso-фазы наиболее эффективна схема выхода в интервал старения, включающая быстрое охлаждение в воде до t_комн от температуры отжига 600 °С и последующий быстрый нагрев до температуры старения 300 °С. Все остальные использованные схемы выхода в интервал старения, включающие медленное охлаждение и/или нагрев, не приводят к формированию рентгенографически идентифицируемого количества ω_iso-фазы. При этом превращение β → ω_iso в интервале температур от 250 до 350 °С имеет выраженную С-образную кинетику с максимумом при 300 °С. Старение во всем интервале t = 250÷350 °С приводит к упрочнению и увеличению твердости сплава по сравнению с исходным состоянием. Причем твердость плавно растет при увеличении температуры старения от 250 до 300 °С и остается постоянной в интервале t = 300÷350 °С. Период решетки β-фазы сплава Ti–22Nb–6Zr остается неизменным во всем температурном интервале старения 250–350 °С, что свидетельствует об отсутствии заметного диффузионного перераспределения элементов в твердом растворе при образовании ω_iso-фазы. Образующаяся в ходе старения сплава Ti–22Nb–6Zr во всем интервале t = 250÷350 °С ω_iso-фаза имеет соотношение с_ω /а_ω = 0,613 ± 0,002, аналогичное соотношению с_ω /а_ω для сдвиговой атермической ω_ath-фазы, что, в свою очередь, дополнительно подчеркивает идентичность этих двух фазовых разновидностей.