INFLUENCE OF DEFORMATION TEMPERATURE ON THE FORMATION OF CONTACTS IN TITANIUM POWDER RIBBONS PRODUCED BY SYMMETRIC AND ASYMMETRIC ROLLING

Abstract

The influence of rolling methods on the mechanical properties of titanium ribbons was studied. Ribbons produced by asymmetric rolling showed 100% density and demonstrated higher strength compared to ribbons rolled symmetrically. The temperature sensitivity of contact formation and mechanical behavior of the ribbons rolled asymmetrically was determined by variations in temperature in the plastic deformation mechanisms of titanium. In this regard, three temperature ranges were selected: low-, intermediate-, and high-temperature ranges. In the low-temperature range (<100 °C), the elastic modulus and the proportionality limit were significantly higher than those resulting from symmetrical rolling, although still inferior to the properties of the compact material. In the intermediate-temperature range (100–300 °C), the elastic modulus and proportionality limit in the rolling direction aligned with the properties of compact titanium but were approximately one-third of those observed in samples tested transversally. In the high-temperature range (>300 °C), the elastic modulus in both the longitudinal and transversal directions was comparable to that of the compact material, while the proportionality limit was considerably higher than that of the compact material as a deformation substructure formed in the ribbons. Asymmetric rolling allowed the mechanical properties of titanium ribbons to be significantly improved compared to symmetric rolling. This was due to the shear strain component that facilitated contact formation at particle boundaries. Under optimal deformation conditions, the ribbons reached a strength limit of ~800 MPa, comparable to the strength of ribbons produced conventionally. The ductility of the ribbons did not exceed 1.5% because of a tendency to interparticle fracture.