Influence of phase composition and microstructure on mechanical properties of hot-rolled Ti-χZr-4Al-0.005B alloys

Abstract

The effects of phase composition and microstructure evolution on mechanical properties of hot-rolled Ti-χZr-4Al-0.005B alloys (abbreviated as, TχZAB with χ = 0, 10, 20, 30, and 40 wt%) were investigated by means of theoretical calculations, optical microscopy, scanning electron microscopy, and transmission electron microscopy. The as-prepared TχZAB alloys showed an excellent combination of the tensile strength and ductility features. For example, the hot-rolled T40ZAB alloy displayed the ultrahigh tensile strength of 1535 MPa at 6.06% elongation. As Zr content increased, the fracture morphologies revealed typical transitional processes from dimple to quasi-cleavage fracture surfaces. The theoretical calculations agreed well with results from X-ray diffraction, where examined alloys showed only α/α′ crystal phases. Under the same hot-rolled condition, the microstructure evolved from distorted (or broken) lamellar α phase to crisscross acicular α′ martensite phase as the Zr content increased. Finally, in search for ideal structural titanium alloys, phase composition and microstructure and relationship with mechanical properties were examined and discussed.