NEAR-BETA TYPE HIGH STRENGTH TI ALLOY MATERIAL EXCELLENT IN FATIGUE CRACK PROPAGATION PROPERTY

摘要

PURPOSE: To impart excellent mechanical strength, particularly, excellent fatigue strength and fatigue crack propagating resist properties to an alloy material and to apply it to the rotating structure of a jet engine by specifying the compsn. of a Ti alloy and forming its metallic structure into an equiaxial αone. ;CONSTITUTION: This alloy material has a compsn. contg., by weight, 4.5 to 5.5% Al, 1.5 to 2.5% Sn, 3.5 to 4.5% Zr, 2.5 to 3.5% Cr, 2.5 to 3.5% Mo, and the balance Ti with inevitable impurities and has a metallic structure of an equiaxial α one. The content of Cr in the compsn. is preferably regulated to 2.6 to 3.4%. The formation of the metallic structure into the equiaxial α one can be attained by sufficiently executing hot finish working, e.g. forge-expanding at the β transformation point or below and thereafter subjecting the same to heat treatment at the β transformation point or below. Ordinary, this heat treatment is constituted of solution treatment and aging treatment.;COPYRIGHT: (C)1996,JPO