Enhanced Strength and Ductility of an Ultrafine-Grained Ti Alloy Processed by HPT

Abstract

We studied the effect of the ultrafine-grained (UFG) structure parameters of the titanium alloy Ti-6Al-4V, processed by high-presure torsion (HPT), on its mechanical properties. The fabrication of alloy with a high strength (σв~ 1700 MPa) and enhanced ductility was demonstrated. The fatique behavior of UFG alloy was also examined.

Microstructural Transformation and Enhanced Strength of Wire‐Feed Electron‐Beam Additive Manufactured Ti–6Al–4V Alloy Induced by High‐Pressure Torsion

“…The obtained microstructure differs from the traditionally observed microstructure of hot-rolled Ti-6Al-4V alloy with (α þ β) structure after HPT. First of all, the difference in the structures is demonstrated in the size of the produced grains, thus in the hot-rolled Ti-6Al-4V alloy after HPT at different regimes the average grain size is from 40 to 100 nm, [3][4][5][6][7][8][9][11][12][13][14] whereas the refinement of grains to 25 AE 10 nm is observed in the Ti-6Al-4V alloy obtained by EBAM and HPT. A more severe refinement of the grain structure of the 3D-printed Ti-6Al-4V samples is due to the presence of highly nonequilibrium martensitic α 0 phase.…”

“…[11][12][13] It is also worth noting the results obtained by the authors in ref. [5], where a hot-rolled alloy with globular α and lamellar (α þ β) initial structure was subjected to HPT at a pressure of 6 GPa and the minimum rotation speed of the billet (0.2 rpm), thus providing the formation of nanostructured state with the highest mechanical strength in the Ti-6Al-4V alloy.…”

“…Thin foils with a diameter of 3 mm for TEM studies were traditionally made from the region at a distance of 5 mm from the sample center (Figure 2b). [1][2][3][4][5][6][7][8][9][10][11][12][13][14] To estimate the average grain size, measurements were taken using the software "GrainSize".…”

“…High-pressure torsion (HPT) is a popular severe plastic deformation (SPD) technique to efficiently refine the microstructure in metallic materials and create ultrafine-grained structure with grain sizes smaller than 100 nm and, therefore, increasing strength properties in such materials. [1,2] The use of HPT to process the titanium alloy Ti-6Al-4V (also often referred as Ti64) was reported in a number of works, [3][4][5][6][7][8][9][10][11][12][13][14] as the alloy is extensively applied in industry and its share constitutes about half of all titanium in commercial production. [15] For example, according to refs.…”

“…[15] For example, according to refs. [5,6] the average grain size in the Ti-6Al-4V alloy produced by hot rolling after ten or more HPT turns varies from 30 to 300 nm depending on the applied pressure. At the same time, the ultimate tensile strength of the Ti-6Al-4V samples increases up to σ UTS = 1740 MPa.…”