CONCERNING THE INFLUENCE OF DEFORMATION RATE ON THE MECHANICAL BEHAVIOR OF THE TI-3.5AL-1.1ZR-2.5V TITANIUM ALLOY UNDER TENSION

The authors studied the rate dependence of the deformation behavior of the circular section samples prepared from the Ti-3.5Al-1.1Zr-2.5V alloy under the uniaxial tension at room temperature. Samples 200 mm long were divided into three groups of five pieces each. The authors tested the first group of samples at a traverse rate of 0.05 mm/min, the second group - at a rate of 5mm/min, and the third group - at a rate of 500 mm/min. The evaluation of the titanium alloy microstructure in the undeformed state showed that the average grain size of the titanium α-phase was about 7 μm, and the grain boundaries were mostly angular, i.e. the neighboring grains were disordered by more than 15°. The mechanical tests showed that the nature of the titanium alloy deformation behavior did not depend on the loading rate. Despite this, the yield and strength limit increased with an increase in the strain rate, while the total strain value decreased. At the place of sample fracture, a neck was observed. The contraction coefficient did not depend on the tensile speed. The authors did not observe any qualitative changes in the mechanical behavior nature and the morphology of the surface of sample fractures (a cup fracture typical for viscous fracture). The study of samples microstructure justifies an increase in the deformability of samples with a decrease in the tensile rate. The width of the diffraction peaks of the samples tested at a lower speed was greater. The fluctuation of the obtained values of the diffraction lines’ width relative to the approximating straight line indicates the speed sensitivity of the grains of “hard” and “soft” orientations. This indicated the existence of the slip system activation sequence. Thus, first of all, “soft” grains are loaded, which are favorably oriented for easy prismatic sliding in the (100) and (110) planes. Then they harden, which contributes to the redistribution of the load on the “hard” grains with basic normals close to the axis of loading, which, at the initial stage, were deformed elastically.

Ti-3,5Al-1,1Zr-2,5V, titanium alloy, tension, destruction, fracture surfaces, Ti-3.5Al-1.1Zr-2.5V