SEQUENCE OF PHASE TRANSFORMATIONS IN THE Ti-6Al-4V ALLOY UPON COOLING FROM THE Β-REGION

В настоящей статье представлены результаты исследования последовательности фазовых превращений в сплаве Ti-6Al-4V при охлаждении на воздухе после термической обработки в β-области. Исследования основаны на анализе микроструктурных характеристик, полученных методами просвечивающей электронной микроскопии (ПЭМ) и энергодисперсионной рентгеновской спектроскопии (ЭДС). В результате исследования было сделано предположение, что распад в сплаве Ti-6Al-4V при охлаждении на воздухе происходит в следующей последовательности: 1) при Тпп высокотемпературная β0-фаза претерпевает распад на α1- и β0-фазы, которые в процессе охлаждения изменяют свой химический состав, преобразуясь в α2- и β1-фазы, химические составы которых существенно отличаются от исходных; 2) при температуре нонвариантного превращения происходит преобразование β1-фазы в α3- и β2-фазы, с выполнением ориентационных соотношений Бюргерса.This paper presents the results of an investigation into the sequence of phase transformations in the Ti-6Al-4V alloy during air cooling after heat treatment in the β-region. The research is based on the analysis of microstructural characteristics obtained through Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray Spectroscopy (EDS). As a result of the study, it is hypothesized that the phase transformatin in the Ti-6Al-4V alloy upon air cooling occurs in the following sequence: 1) at the β-transus temperature, the high-temperature β₀-phase undergoes decomposition into α₁- and β₀-phases. During cooling, these phases modify their chemical compositions, transforming into the α₂- and β₁-phases, which chemical compositions significantly differ from the parent ones. At the non-variant transformation temperature, the β₁-phase is transformed into the α₃- and β₂-phases according to the Burgers Orientation Relationships

A Review—Additive Manufacturing of Intermetallic Alloys Based on Orthorhombic Titanium Aluminide Ti2AlNb

Titanium alloys based on orthorhombic titanium aluminide Ti2AlNb are promising refractory materials for aircraft engine parts in the operating temperature range from 600–700 °C. Parts made of Ti2AlNb-based alloys by traditional technologies, such as casting and metal forming, have not yet found wide application due to the sensitivity of processability and mechanical properties in chemical composition and microstructure compared with commercial solid-solution-based titanium alloys. In the last three decades, metal additive manufacturing (MAM) has attracted the attention of scientists and engineers for the production of intermetallic alloys based on Ti2AlNb. This review summarizes the recent achievements in the production of O-phase-based Ti alloys using MAM, including the analysis of the feedstock materials, technological processes, machines, microstructure, phase composition and mechanical properties. Powder bed fusion (PBF) and direct energy deposition (DED) are the most widely employed MAM processes to produce O-phase alloys. MAM provides fully dense, fine-grained material with a superior combination of mechanical properties at room temperature. Further research on MAM for the production of critical parts made of Ti2AlNb-based alloys can be focused on a detailed study of the influence of post-processing and chemical composition on the formation of the structure and mechanical properties, including cyclic loading, fracture toughness, and creep resistance