# Designing Ductile 2‐GPa Yielding Titanium Alloys via Multifunctional Subgrain Boundaries and Nanoprecipitates

## TL;DR

This paper presents a new titanium alloy design that achieves ultra-high strength and ductility by using engineered subgrain boundaries and nanoprecipitates.

## Contribution

The novel strategy combines ultrafine β-subgrains and α-nanoprecipitates to achieve a rare combination of high strength and ductility in titanium alloys.

## Key findings

- A Ti-4Al-5Mo-3V-5Cr-1Fe alloy achieved a yield strength of ≈1929 MPa and uniform elongation of ≈6.2%.
- The microstructure impedes dislocation motion and enables sustained work hardening through local chemical heterogeneities.
- The strategy is promising for other metallic materials, especially additively manufactured alloys.

## Abstract

Ductile titanium alloys yielding at 2 GPa are rarely achieved via strengthening of hexagonal close‐packed α‐nanoprecipitates, which suffer from the planar glide softening to cause strain localization for insufficient work hardening capability. In this study, by engineering multifunctional β‐subgrain boundaries, an unprecedented combination of ultra‐high yield strength ≈1929 MPa and ultimate strength ≈2014 MPa, along with a notable uniform elongation ≈6.2%, is successfully achieved in a Ti‐4Al‐5Mo‐3V‐5Cr‐1Fe alloy. This superior mechanical performance is enabled by a unique microstructure featured with ultrafine β‐subgrains containing intragranular α‐nanoprecipitates and intergranular discrete α‐nanolaths. The resulting complex, multiscale hierarchical architecture effectively impedes and regulates dislocation motion, thereby endowing the alloys synergistic strengthening and ductilizing. Furthermore, local chemical heterogeneities combined with high stress‐driven elemental partitioning exert strong nanoscale segment detrapping effects on mobile dislocations, contributing to a sustained work hardening rate and thus large uniform elongation. This multifunctional subgrain boundary strategy holds significant promise for extension to other metallic materials, particularly these additively manufactured alloys with dense dislocation cells, toward achieving ultrastrong‐yet‐ductile performance.

By engineering ultrafine β‐subgrains and nanoscale α‐precipitates in titanium alloys, the unique architecture achieves an unprecedented ultra‐high strength of 2 GPa while maintaining a notable uniform elongation of 6%, a combination that is both rare and highly promising for structural applications of titanium alloys. This microstructure design strategy holds significant potential for extension to other metallic materials, enabling superior strength‐ductility synergy.