Designing ultra-strong and ductile hierarchical titanium alloys via interstitial solute-mediated multi-morphologic α-nanoprecipitates

In conventional duplex titanium (Ti) alloys, the soft primary & alpha;-precipitates (& alpha;p) are beneficial to ductility with the loss of high yield strength, while the continuous & alpha;-precipitates at grain boundaries (GBs, & alpha;GBs) often accompanied with & alpha; precipitate-free zones (& alpha;-PFZs) renders the strain incompatibility for limited ductility. Here, to overcome this longstanding issue, we utilize interstitial (O and N) atoms to notably strengthen the & alpha;-phase, and simultaneously architect the multi-morphologic secondary & alpha;-precipitates (& alpha;s) so as to improve the strain compatibility nearby GBs, thus develop a Ti-4.1Al-2.5Zr-2.5Cr-6.8Mo (wt.%) alloy with ultra-high yield strength of -1580 MPa and good ductility of -8.2%. The phase boundaries between the hard & alpha;-precipitates and the soft & beta;-matrix not only act as dislocation barriers for strengthening, but also as sustainable dislocation sources for ductilizing to achieve a good combination of strength and ductility in our Ti alloys. This strategy not only sheds light on the understanding of the strength-ductility synergy of duplex Ti alloys, but also offers an available pathway to design ultra-strong and ductile alloys.

Automated summary

In this study, we have utilized interstitial atoms to strengthen the α-phase and architect multi-morphologic secondary α-precipitates, resulting in a titanium alloy with ultra-high yield strength and good ductility. This strategy not only sheds light on the strength-ductility synergy of duplex titanium alloys, but also provides a feasible pathway for designing ultra-strong and ductile alloys.