The Effect of Percentage of Primary α on Mechanical Properties of Bimodal Microstructure of TC4

Abstract

In order to discuss the effect of content of primary α on properties of bimodal microstructure, the TC4 sheet in rolling state was heat treated at different temperatures of 10~50°Cbelow the β-transus temperature, then a series of bimodal microstructures with different content of primary α were obtained by air-cooled procedure. Quasi-static and dynamic compress tests were carried out with universal material testing machine and Split Hopkinson Pressure Bar (SHPB) respectively. The results indicated that the relationship between mechanical properties and primary α is irregular, and that bimodal microstructure with 25% primary α shows a better combination of strength and ductility.

Mechanical properties of near alpha titanium alloys for high-temperature applications - a review

“…Lamellar microstructure enhances fatigue crack growth (FCG) and creep resistances (Hosseini et al , 2017). Yang et al (2012) reported 25 per cent of primary α phase in the microstructure of Ti-64 preceding solution treatment showed a combination of high strength and ductility. Shi et al (2017) used the solution treatment followed by oil cooling to obtain a better proportion of primary and lamellar α phases in the Ti-8Al-1Mo-1V alloy.…”

“…Ductility of Ti-64 (HPT + annealing), as well as Ti-600 (forged/aged/solution) alloys, are higher than Ti-6242S (rolled + annealed) because of possibly the processing route. Alloys with bimodal microstructure have higher yield strength and ductility, and increasing solution temperature from α + β phase field to single β phase field leads to a reduction in ductility (Hosseini et al , 2017; Yang et al , 2012).…”

“…Solution treatment is extensively reported to affect the type of microstructure in near- α Ti alloys. When the solution temperature is below β phase transus, bimodal microstructure consisting of equiaxial α phase and “basket weave” (widmanstätten) structures are prominent (Hosseini et al , 2017; Li et al , 2011; Yang et al , 2012). This microstructure shows high strength and ductility of the alloys.…”