Unravelling the competitive effect of microstructural features on the fracture toughness and tensile properties of near beta titanium alloys. (20th January 2022)

• Record Type: Journal Article
• Authors: Liu, Yang; Lim, Samuel C.V.; Ding, Chen; Huang, Aijun; Weyland, Matthew
• Is Part Of: Journal of materials science & technology. Volume 97(2022)
• Page Start: 101
• Page End: 112
• Publication Date: 2022-01-20
• Subjects: Near β titanium alloys -- Microstructural features -- Competitive effect -- Fracture toughness -- β grain size effect; Metals -- Periodicals; Materials science -- Periodicals; Materials science; Metals; Periodicals; 620.1105
• DOI: 10.1016/j.jmst.2021.04.032
• Languages: English
• ISSNs: 1005-0302

Abstract

Highlights: The relative importance of β grain size and STA process parameters were analyzed using an orthogonal array method. The relationship between specific microstructural features with strength, ductility and fracture toughness were established. The contradictory β grain size effect on fracture toughness was explained. A table was proposed to quasi-quantitatively unravel the competitive effect of microstructural features. Abstract: The competitive effect of microstructural features including primary α (αp ), secondary α (αs ), grain boundary α (αGB ) and β grain size on mechanical properties of a near β Ti alloy were studied with two heat treatment processes. The relative effect of β grain size and STA (solution treatment and ageing) processing parameters on mechanical properties were quantitatively explored by the application of Taguchi method. These results were further explained via correlating microstructure with the fracture toughness and tensile properties. It was found that large numbers of fine αs precipitates and continuous αGB played greater roles than other features, resulting in a high strength and very low ductility (<2%) of STA process samples. The β grain size had a negative correlation with fracture toughness. In the samples prepared by BASCA (β anneal slow cooling and ageing) process, improved ductility and fracture toughness were obtained due to a lower density of αs precipitates, a basket-weave structure and zigzag morphology of αGB . For this heat treatment, an increase in prior β grain size had an observable positive effect on fracture toughness. The contradictory effect of β grain size on fracture toughness found in literature was for the first time explained. It was shown that the microstructure obtained from different processes after β solution has complex effect on mechanical properties. This complexity derived from the competition between microstructure features and the overall sum of their effect on fracture toughness and tensile properties. A novel table was proposed to quasi-quantitatively unravel these competitive effects.