Effect of duplex aging on microstructure and mechanical behavior of beta titanium alloy Ti–15V–3Cr–3Al–3Sn under unidirectional and cyclic loading conditions

•Duplex aging (DA) in place of single aging (SA) of beta titanium alloy 15-3 led to higher strength.•Higher strength after DA was related to finer and denser precipitation of α particles.•DA resulted in major improvement in HCF life over SA.•Freedom from micro-PFZs and grain boundary α led to better HCF life after DA.•Improved HCF life after DA was achieved even at a high mean stress level (stress ratio = +0.3).

The microstructure and mechanical behavior of beta titanium alloy Ti–15V–3Cr–3Al–3Sn (Ti15-3) under unidirectional and high cycle fatigue (HCF) loading conditions were studied after single aging (SA) and duplex aging (DA). After SA, well-developed grain boundary α and micro precipitate free zones (micro PFZs) were present in the microstructure. Whereas after DA, grain boundary α was poorly developed and micro PFZs were absent. DA resulted in smaller size, higher density and volume fraction of alpha particles. DA led to higher work hardening rate, better strength-ductility combination and higher HCF life. Improved mechanical behavior after DA is explained based on microstructural observations.