Influence of Phase Composition and Microstructure on Mechanical Behaviour of the Metastable Ti—3Al—4.5Fe—7.2Cr and VT22 Titanium β-Alloys under Tension with Different Rates

Taking two metastable β-titanium alloys VT22 (Ti—5 (% wt.) Al—5V—5Mo— 1Fe—1Cr) and Ti—3Al—4.5Fe—7.2Cr as program materials, the influence of β-grain size, phase composition, and strain rate (in the range of 3.20∙10⁻⁵ up to 1.81∙10⁻¹) on alloys’ mechanical behaviour is investigated. The mechanical behaviour of both alloys in as-quenched single-phase β-state is similar to another metastable β-alloy TIMETAL-LCB: ductility and tensile toughness are monotonously decreased with strain rate. Ageing causes increase in strength and decrease in ductility, whereas the drop of the latter is the most pronounced in both the coarse-grained VT22 alloy and the Ti—3Al—4.5Fe—7.2Cr one regardless of grain size. As suggested, the reason of this effect is the formation of thin layers enriched by β-stabilizing elements located close to grain-boundary α-phase. Taking into account drastic embrittlement of Ti— 3Al—4.5Fe—7.2Cr alloy, which contains only β-eutectoid alloying elements, this enrichment can lead to the precipitation of intermetallics.На прикладі двох промислових титанових стопів метастабільного β-класу ВТ22 (Ti—5(%мас.) Al—5V—5Mo—1Fe—1Cr) та Ti—3Al—4,5Fe—7,2Cr було вивчено вплив розміру β-зерен, фазового складу та швидкости деформації на розтяг (у діяпазоні від 3,20∙10⁻⁵ до 1,81∙10⁻¹) на їхню механічну поведінку. Механічна поведінка обох стопів, загартованих на однофазний метастабільний β-стан, є аналогічною до іншого титанового β-стопу TIMETAL-LCB: характеристики пластичности та в’язкости руйнування монотонно зменшуються з ростом швидкости деформації. Наступне старіння приводить до росту характеристик міцности та зниження пластичности, причому падіння показників останньої є найбільшим у стопу ВТ22 з грубим зерном та у стопу Ti—3Al—4,5Fe—7,2Cr незалежно від розміру зерна. Запропоновано висновок про те, що причиною цього є формування тонких шарів, збагачених β-стабілізувальними елементами, які утворюються безпосередньо біля α-пластин, що покривають межі β-зерен. Із врахуванням критичного окрихчування стопу Ti—3Al—4,5Fe—7,2Cr, який вміщує виключно β-стабілізувальні леґувальні елементи евтектоїдного типу, висловлено припущення про те, що подібне збагачення може приводити до локального утворення інтерметалідів.На примере двух промышленных титановых сплавов метастабильного β-класса ВТ22 (Ti—5 (% мас.) Al—5V—5Mo—1Fe—1Cr) и Ti—3Al—4,5Fe—7,2Cr было изучено влияние размера β-зёрен, фазового состава и скорости деформации растяжением (в диапазоне от 3,20∙10⁻⁵ до 1,81∙10⁻¹) на их механическое поведение. Механическое поведение обоих сплавов, закалённых на однофазное метастабильное β-состояние, является аналогичным поведению другого титанового β-сплава TIMETAL-LCB: характеристики пластичности и вязкости разрушения монотонно снижаются с ростом скорости деформации. Последующее старение приводит к росту характеристик прочности и снижению пластичности, причём падение показателей последней является наибольшим у сплава ВТ22 с крупным зерном, а у сплава Ti—3Al—4,5Fe—7,2Cr не зависит от размера зерна. Предложен вывод о том, что причиной этого является формирование тонких слоёв, обогащённых β-стабилизирующими элементами, которые образуются непосредственно возле α-пластин, покрывающих границы β-зёрен. С учётом критического охрупчивания сплава Ti—3Al—4,5Fe—7,2Cr, который содержит исключительно β-стабилизирующие легирующие элементы эвтектоидного типа, было высказано предположение о том, что подобное обогащение может приводить к локальному образованию интерметаллидов

Effect of microstructure, deformation mode and rate on mechanical behaviour of electron-beam melted Ti-6Al-4V and Ti-1.5Al-6.8Mo-4.5Fe alloys

Two commercial costefficient titanium alloys—a lowalloyed α+βti–6Al–4V (mas.%) and a metastable βalloy ti–1.5Al–6.8Mo–4.5Fe melted with a single electronbeam cold hearth melting approach—are employed in a present study as program materials. the influence of microstructure formed by means of the subsequent thermomechanical and heat treatments on both the mechanical behaviour (evaluated by the deformation energy, UD) when tested using standard methods with different deformation rates and the ballistic resistance of plate materials is investigated.На прикладі двох промислових економно леґованих титанових стопів, — малолеґованого α + β-стопу ti–6Al–4V (мас.%) і метастабільного βстопу ti–1,5Al–6,8Mo–4,5Fe, — виготовлених одноразовим електроннопроменевим топленням з проміжною ємністю, вивчено вплив формованої за подальших (термомеханічного та термічного) оброблянь мікроструктури на механічну поведінку (виражену через енергію деформації UD) при випробуваннях з різними швидкостями деформації та балістичну стійкість.На примере двух промышленных экономно легированных титановых сплавов, — малолегированного α + βсплава Тi–6Al–4V (масс.%) и метастабильного βсплава ti–1,5Al–6,8Mo–4,5Fe, — приготовленных однократной электроннолучевой плавкой с промежуточной ёмкостью, изучено влияние формируемой при последующих (термомеханической и термической) обработках микроструктуры на механическое поведение (выраженное через энергию деформации UD) при ис пы таниях с разными скоростями деформации и баллистическую стойкость

Microstructure and properties of titanium-based materials promising for antiballistic protection

Titanium-based materials, which combine high strength and hardness of surface layer along with sufficient ductile characteristics of the matrix metal, are very promising for various applications, particularly, as armoured components in military-industrial complex. Above-mentioned combination of properties can be achieved by means of the creation of multilayer structures, which consist of layers possessing different physical and mechanical properties. In the present study, microstructure peculiarities, mechanical and antiballistic protection properties of the layered Tibased materials are investigated. Two different ways were used for fabrication of such the layered structures.Титанові матеріaли, які поєднують високу міцність і твердість поверхні при достатніх пластичних характеристиках основного металу, є перспективними для використання в різних галузях техніки, зокрема, в якості бронеелементів у військово-промисловому комплексі. Одержати вищевказану комбінацію властивостей можливо, створюючи матеріaли, які складаються з декількох шарів, що відрізняються за своїми фізико-механічними характеристиками. В роботі досліджено особливості мікроструктури, механічних характеристик і балістичної стійкості таких матеріaлів, створених за двома підходами.Титановые материалы, которые совмещают высокую прочность и твёрдость поверхности при достаточных пластических характеристиках основного металла, являются перспективными для использования в различных областях техники, в частности, как бронеэлементы в военно-промышленном комплексе. Достичь такой комбинации свойств возможно, создавая материалы, состоящие из нескольких слоёв, которые отличаются по своим физико-механическим характеристикам. В работе исследованы особенности микроструктуры и механических характеристик таких материалов, созданных двумя путями

Electron Beam Cold Hearth Melted Titanium Alloys and the Possibility of Their Use as Anti-Ballistic Materials

Three commercial titanium alloys: two-phase α+β Ti-6Al-4V (low alloyed), and T110 (Ti-5.5Al-1.5V-1.5Mo-4Nb-0.5Fe, higher-alloyed), and β-metastable Ti-1.5Al-6.8Mo-4.5Fe were melted using EBCHM approach in the form of 100 mm in diameter ingots with the weight of about 20 kg each. After 3D hot pressing at single β-field temperatures ingots were rolled at temperatures below β-transus onto plates with thickness varying from 3 mm to 25 mm. Different heat treatments, including annealing at α+β or β-field temperatures, and special strengthening Surface Rapid Heat Treatment (SRHT) which after final aging provided special gradient microstructure with a hardened surface layer over ductile basic core, were employed. Mechanical properties were studied with tensile and 3-point flexure tests. It was established that the best combination of tensile strength and ductility in all alloys studied was obtained after SRHT, whereas at 3-point flexure better characteristics were obtained for the materials annealed at temperatures of (α+β)-field. At the same time, ballistic tests made at a certified laboratory with different kinds of ammunition showed essential superiority of plates having upper layers strengthened with SRHT. The effect of microstructure of the alloys, plate thickness and type of used ammunition on ballistic resistance is discussed

Electron Beam Cold Hearth Melted Titanium Alloys and the Possibility of Their Use as Anti-Ballistic Materials

Three commercial titanium alloys: two-phase α+β Ti-6Al-4V (low alloyed), and T110 (Ti-5.5Al-1.5V-1.5Mo-4Nb-0.5Fe, higher-alloyed), and β-metastable Ti-1.5Al-6.8Mo-4.5Fe were melted using EBCHM approach in the form of 100 mm in diameter ingots with the weight of about 20 kg each. After 3D hot pressing at single β-field temperatures ingots were rolled at temperatures below β-transus onto plates with thickness varying from 3 mm to 25 mm. Different heat treatments, including annealing at α+β or β-field temperatures, and special strengthening Surface Rapid Heat Treatment (SRHT) which after final aging provided special gradient microstructure with a hardened surface layer over ductile basic core, were employed. Mechanical properties were studied with tensile and 3-point flexure tests. It was established that the best combination of tensile strength and ductility in all alloys studied was obtained after SRHT, whereas at 3-point flexure better characteristics were obtained for the materials annealed at temperatures of (α+β)-field. At the same time, ballistic tests made at a certified laboratory with different kinds of ammunition showed essential superiority of plates having upper layers strengthened with SRHT. The effect of microstructure of the alloys, plate thickness and type of used ammunition on ballistic resistance is discussed

Structure and Properties of Layered Ti-6Al-4V-Based Materials Fabricated Using Blended Elemental Powder Metallurgy

Due to the high specific strength of Ti, materials on its base are indispensable when high-strength and low-weight requests are a chief demand from the industry. Reinforcement of Ti-alloys with hard and light particles of TiC and TiB is a credible pathway to make metal matrix composites (MMC) with enhanced elastic moduli without compromising the material’s low-weight. However, reinforcement of the alloy with hard particles inevitably lowers the value of toughness and plasticity of material. Yet, in many applications simultaneous high hardness and high plasticity are not required through the entire structure. For instance, parts that need enhanced wear resistance or resistance upon ballistic impact demand high hardness and strength at the surface, whereas their core necessitates rather high toughness and ductility. Such combination of mechanical properties can be achieved on layered structures joining two and more layers of different materials with different chemical composition and/or microstructure within each individual layer. Multi-layered structures of Ti-6Al-4V alloy and its metal-matrix composites (MMC) with 5 and10% (vol.) of TiC and TiB were fabricated in this study using blended elemental powder metallurgy (BEPM) of hydrogenated Ti. Post-sintering hot deformation and annealing were sometimes also employed to improve the microstructure and properties. Structure of materials were characterized using light optical microscopy, scanning electron microscopy, electron backscattered diffraction, x-ray microscopy, tensile and 3-point flexural tests. The effect of various fabrication parameters was investigated to achieve desirable microstructure and properties of layered materials. Using optimized processing parameters, relatively large multilayered plates were made via BEPM and demonstrate superior anti-ballistic performance compared to the equally sized uniform Ti-6Al-4V plates fabricated by traditional ingot and wrought technology

Structure and Properties of Layered Ti-6Al-4V-Based Materials Fabricated Using Blended Elemental Powder Metallurgy

Due to the high specific strength of Ti, materials on its base are indispensable when high-strength and low-weight requests are a chief demand from the industry. Reinforcement of Ti-alloys with hard and light particles of TiC and TiB is a credible pathway to make metal matrix composites (MMC) with enhanced elastic moduli without compromising the material’s low-weight. However, reinforcement of the alloy with hard particles inevitably lowers the value of toughness and plasticity of material. Yet, in many applications simultaneous high hardness and high plasticity are not required through the entire structure. For instance, parts that need enhanced wear resistance or resistance upon ballistic impact demand high hardness and strength at the surface, whereas their core necessitates rather high toughness and ductility. Such combination of mechanical properties can be achieved on layered structures joining two and more layers of different materials with different chemical composition and/or microstructure within each individual layer. Multi-layered structures of Ti-6Al-4V alloy and its metal-matrix composites (MMC) with 5 and10% (vol.) of TiC and TiB were fabricated in this study using blended elemental powder metallurgy (BEPM) of hydrogenated Ti. Post-sintering hot deformation and annealing were sometimes also employed to improve the microstructure and properties. Structure of materials were characterized using light optical microscopy, scanning electron microscopy, electron backscattered diffraction, x-ray microscopy, tensile and 3-point flexural tests. The effect of various fabrication parameters was investigated to achieve desirable microstructure and properties of layered materials. Using optimized processing parameters, relatively large multilayered plates were made via BEPM and demonstrate superior anti-ballistic performance compared to the equally sized uniform Ti-6Al-4V plates fabricated by traditional ingot and wrought technology