The key approach to fabricate ultra-high strength dual-phase titanium alloys and its practice

In recent times, many researchers have done a lot of work on microstructure control and composition adjustment to obtain ultra-high strength dual-phase titanium alloys, but there has been almost no research that can elucidate the key factor affecting the strength of dual-phase titanium alloys. This article investigates the effects of five common microstructural parameters on the yield strength, indicating that compared to the other 4 variables, the α lamellar thickness is the key factor affecting the strength of titanium alloys. Refining the size of α-lamellae to the nanoscale while ensuring a relatively low content of the equiaxed α-phase is the key approach for obtaining ultra-high strength in dual-phase titanium alloys. To validate this result, the 2.5 kg Ti-3.2Cr-4.4Zr-5.4Al alloy ingot was used as a practice alloy, showing that when the α lamellar thickness was 56 nm and the volume fraction of the primary α phase was only 17.6%, the yield strength reached 1615 MPa. This study provides a clear and feasible pathway to obtain ultra-high strength dual-phase titanium alloys.