Frontier Materials & TechnologiesFrontier Materials & TechnologiesFrontier Materials & Technologies2782-40392782-6074Togliatti State University15710.18323/2073-5073-2021-3-84-90ArticlesСтатьиEffect of γ′-phase particles on the mechanical behavior and deformation mechanism of (CoCrFeNi)94Ti2Al4 high entropy alloy single crystalsВлияние частиц γ′-фазы на механическое поведение и механизм деформации монокристаллов высокоэнтропийного сплава (CoCrFeNi)94Ti2Al4https://orcid.org/0000-0002-0812-2323SaraevaAnastasia A.СараеваАнастасия Александровна
Russian Federation

postgraduate student of Chair of Metal Physics, research engineer of the Laboratory of High-Strength Crystals

аспирант кафедры физики металлов, инженер-исследователь лаборатории физики высокопрочных кристаллов

Anastasia16-05@yandex.ruNational Research Tomsk State University, Tomsk (Russia)Национальный исследовательский Томский государственный университет, Томск (Россия)30092021384903009202130092021https://vektornaukitech.ru/jour/article/view/157

Recently, the interest of researchers has focused on a new FCC class (FCC – face-centered cubic lattice) high-entropy alloys (HEA), due to their unique properties – high values of the strain hardening coefficient, good plasticity, and ductile fracture at low test temperatures. Such a combination of properties in an FCC of HEA is achieved by mixing five or more elements in equal atomic proportions. Due to the strong temperature dependence of stresses at the σ0.1(T) yield point, these alloys have low σ0.1 values at temperatures above room temperature, which hinders their practical application. A precipitation hardening is an effective way to achieve high strength and is successfully used for hardening HEA FCC. The paper studied the influence of ageing at 923 K for 4 hours and at 1073 K for 18 and 30 hours on the mechanical behavior of single crystals of (CoCrFeNi)94Ti2Al4 (at.%) HEA FCC oriented along the [001] direction under tension. Ageing at 923 K for 4 hours and at 1073 K for 18 and 30 hours leads to the precipitation of γ′-phase particles, the size and volume fraction of which depend on the ageing temperature and time. The γ′-phase particles precipitation leads to an increase in stresses at the yield point from 47 MPa (ageing at 923 K, 4 hours) to 226 MPa (ageing at 1073 K, 30 hours) relative to quenched crystals at 296 K. The study identified the dependence of the strain hardening coefficient, plasticity, and the maximum stress level before fracture on heat treatment. The author discussed the reasons for the growth of stresses at the yield point and the strain hardening coefficient upon precipitation of γ′-phase particles. 

В последнее время интерес исследователей сфокусирован на новом классе гранецентрированных кубических решеток (ГЦК) высокоэнтропийных сплавов (ВЭС), благодаря их уникальным свойствам – высоким значениям коэффициента деформационного упрочнения, хорошей пластичности и вязкому разрушению при низких температурах испытания. Такое сочетание свойств в ГЦК ВЭС достигается в результате смешивания пяти и более элементов в равных атомных пропорциях. Из-за сильной температурной зависимости напряжений на пределе текучести σ0,1(Т), эти сплавы характеризуются низкими значениями σ0,1 при температуре выше комнатной, что сдерживает их практическое применение. Дисперсионное упрочнение является эффективным способом достижения высокой прочности и успешно применяется для упрочнения ГЦК ВЭС. В работе проведены исследования влияния старения при 923 К в течение 4 ч и при 1073 К в течение 18 и 30 ч на механическое поведение монокристаллов ГЦК (CoCrFeNi)94Ti2Al4 (ат. %) ВЭС, ориентированных вдоль [001] направления, при растяжении. Старение при 923 К в течение 4 ч и при 1073 К в течение 18 и 30 ч приводит к выделению частиц γ′-фазы, размер и объемная доля которых зависят от температуры и времени старения. Выделение частиц γ′-фазы приводит к росту напряжений на пределе текучести от 47 МПа (старение 923 К, 4 ч) до 226 МПа (старение 1073 К, 30 ч) относительно закаленных кристаллов при 296 К. Установлена зависимость коэффициента деформационного упрочнения, пластичности и максимального уровня напряжений до разрушения от термической обработки. Обсуждаются причины роста напряжений на пределе текучести и коэффициента деформационного упрочнения при выделении частиц γ′-фазы.

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