Hot Processing of Powder Metallurgy and Wrought Ti-6Al-4V Alloy with Large Total Deformation: Physical Modeling and Veri

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THE most common group of titanium alloys is dual-phase alloys. They are mainly used in the aviation, automotive, defense, shipbuilding, medicine and many other branches of industry.[1–5] The attractiveness of these materials is primarily due to the properties of titanium, among which are low density, high strength, resistance to cracking, corrosion and fatigue strength.[2,6] Some of the titanium alloys maintain high strength under dynamic loads[1,7,8]; others are biocompatible and resistant to corrosion in a biological environment, which allows their use in the manufacturing of implants.[9–13] The significant disadvantages of titanium and its alloys include low thermal conductivity, difficulties in their machining[14–16] and relatively high MAREK WOJTASZEK, TOMASZ S´LEBODA and KRYSTIAN ZYGUŁA are with the Faculty of Metals Engineering and Industrial Computer Science, AGH University of Science and Technology, Al. A. Mickiewicza 30, 30-059 Krako´w, Poland. Contact e-mail: [email protected] GRZEGORZ KORPAŁA and ULRICH PRAHL are with the Institut fu¨r Metallformung, Technische Universita¨t Bergakademie Freiberg, Bernhard-Von-Cotta Str. 4, 09-599 Freiberg, Germany. Manuscript submitted April 4, 2020.

METALLURGICAL AND MATERIALS TRANSACTIONS A

production costs.[1,17–19] At present, a semi-finished product in the form of the processed cast material is commonly used for the production of highly responsible titanium alloy structural parts.[1] However, attempts are being made to replace it by using the powder metallurgy methods,[9,17,20,21] because it reduces production costs. Cost reduction can be achieved by using inexpensive initial material, implementing waste-free processes and conducting processes at lower temperatures compared to the methods based on casting. Among the downsides resulting from the use of powder metallurgy technology for the production of titanium alloys, the most important is the occurrence of porosity and limitation of the size and shape of the products.[22] When using initial materials in the form of elemental powders, there is also the risk of inhomogeneity of the chemical composition in the volume of the products. However, the occurrence of these faults can be prevented by proper selection of the method of mixing the powders and by including hot processing of the semi-finished products in the production chain. Among the dual-phase titanium alloys, Ti-6Al-4V is the most widely applied. In addition to titanium-specific advantages, it also exhibits heat resistance, good weldability and good ductility.[1] Additionally, good formability of the investigated material means that under

appropriately selected conditions it can be processed in commonly used metal-forming processes.[23] Therefore, if responsible structural parts are produced in this way, it is necessary to know the combinations of thermomechanical parameters that lead to obtaining products that are free of defects with an assumed geometry as well as to obtaining a microstructure that guarantees high mechanical and functional properti