Study on microstructure evolution, mechanical properties and deformation mechanism of Ti-6Al-4V alloy by hydraulic tension on-line warm rolling

Abstract

In this research, Ti-6Al-4 V alloy thin strip with ultra-high tensile strength and good ductility combination was successfully prepared by a new high-efficiency short-flow on-line warm rolling processing method. To explore the intricate relationships between microstructure evolution, mechanical characteristics, and the deformation mechanism during on-line warm rolling of the Ti-6Al-4 V alloy, various analytical methods were employed, including OM, SEM, XRD, EPMA, EBSD, and TEM. When the rolling reduction escalated from a Warm Rolling (WR) rate of 70–90%, there was a concurrent increase in both the alloy's strength and ductility. In numerical terms, the ultimate tensile strength, yield strength, and total elongation rose from 1241 MPa, 1117 MPa, and 5.3% respectively at WR-70%, to 1366 MPa, 1214 MPa, and 8.2% at WR-90%. At WR-90%, the high strength of the resulting Ti-6Al-4 V alloy thin strip is ensured through a distinct combination of material adaptations. These include grain refinement, high-density dislocation accumulation, and the presence of both partial fine recrystallization and ultrafine grains. The initiation of the pronounced basal slip system {0001}< 11–20 > coupled with the pyramidal system {11−22}< 11–2–3 > plays a pivotal role in retaining ductility even under conditions of elevated strength. The amalgamation of grain refinement, dense dislocation accumulation, and the juxtaposition of partial fine recrystallization with ultrafine grains, in tandem with the prevailing basal slip system {0001}< 11–20 > and the active pyramidal system {11−22}< 11–2–3 > , ensures the preservation of commendable ductility while simultaneously achieving high strength. This successful creation of the high-performance Ti-6Al-4 V alloy thin strip provides crucial parameters and theoretical guidance for the industrial application of the hydraulic tension on-line warm rolling method for titanium alloys and other similarly difficult-to-deform metals.