The composition rule of near-a Ti alloy Ti1100 was investigated using a cluster-plus-glue-atom model for solid-solution alloys, and its cluster formula could be expressed as [Al-（Ti13.7Zr0.3）]（Alo.69Sno.18Moo.03Sio.12） A new series of alloys by adding minor Hf, Ta andNb with similar elements substitution in equimolar ratio were then designed, being [Al-（Ti13.7Zr0.15Hf0.15）]（A10.69Sn0.1sSi0.1（Mo/Ta/Nb）o.o3） These alloys were solid-solution-treated at 950 ℃ for 1 h followed by water-quenching, and then aged at 560 ℃ for 6 h. Subsequently, the microstructures, microhardness, elevated temperature oxidation- and corrosion-resistance of the alloys were measured. The results show that the alloy with Hf0.15 substitution for Zr0.15 in Till00 still exhibits a fl-transformed lamellar microstructure, while the further combinations of Ta and Nb induce a large amount of equiaxed a grains to form a duplex microstructure. The change of microstructure hardly affects the microhardness of the alloys, within a range of 3300-3700 MPa. All the designed alloys, as well as the reference Ti1100, possess excellent oxidation-resistance at 650 ℃, and all the oxidation mass gains are less than 1.0 mg/cm2. But the results are obviously different in comparison with that of Till00 at 800 ~C. The oxidation mass gains of the designed alloys with Hf, Ta and Nb co-alloying after 100 h are significantly fewer, and the widths of the dense oxidation layers are among 23-27 ktm. The [Al-（Ti13.TZr0.15Hf0.15）]（A10.69Sn0.18Si0.1Ta0.015Nb0.015） alloy has the best oxidation resistance with the fewest oxidation mass gain of 2.6 mg/cm2. In addition, this series of alloys also have good corrosion resistance in 3.5%NaC1.
Rare Metal Materials and Engineering
near-α Ti alloys
minor-addition of elements