The goal of the present work is a systematic study on an influence of a strain rate on the mechanical response and microstructure evolution of the selected titanium-based materials, i.e., commercial pure titanium, Ti-6Al-4V alloy with lamellar and globular microstructures produced via a conventional cast and wrought technology, as well as Ti-6Al-4V fabricated using blended elemental powder metallurgy (BEPM). The quasi-static and high-strain-rate compression tests using the split Hopkinson pressure bar (SHPB) technique were performed and microstructures of the specimens were characterized before and after compression testing. The strain rate effect was analyzed from the viewpoint of its influence on the stress–strain response, including the strain energy, and a microstructure of the samples after compressive loading. It was found out that the Ti-6Al-4V with a globular microstructure is characterized by high strength and high plasticity (ensuring the highest strain energy) in comparison to alloy with a lamellar microstructure, whereas Ti6-Al-4V obtained with BEPM reveals the highest plastic flow stress with good plasticity at the same time. The microstructure observations reveal that a principal difference in high-strain-rate behavior of the tested materials could be explained by the nature of the boundaries between the structural components through which plastic deformation is transmitted: α/α boundaries prevail in the globular microstructure, while α/β boundaries prevail in the lamellar microstructure. The Ti-6Al-4V alloy obtained with BEPM due to a finer microstructure has a significantly better balance of strength and plasticity as compared with conventional Ti-6Al-4V alloy with a similar type of the lamellar microstructure.
Blended elemental powder metallurgy using titanium hydride and Al-Fe-Cr master alloy powders was employed to produce a new Ti-1.5Al-1Fe-7.2Cr (wt.%) transition a ? b/b metastable-type alloy. A simple process involving blending, cold pressing, and sintering resulted in a material with a residual porosity of not higher than 3.9-5%, a uniform and relatively fine-grained microstructure (average b-grain size of less than 100 lm), and acceptable mechanical properties. The influence of subsequent annealing and hot pressing on the microstructure evolution and porosity reduction was investigated. The results indicated that optimized regimes of hot deformation and heat treatment produced a structural state with a good combination of strength (UTS = 970 MPa) and ductility (El = 14.7%, RA = 35%).Keywords Low-cost titanium alloy Á Microstructure Á Mechanical properties Á Blended elemental powder metallurgy Á Thermomechanical treatment Á Fracture Á Phase composition
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