FRACTURE-TOUGHNESS OF TI-46.5AL-2.1CR-3.0NB-0.2W FROM FINITE-ELEMENT ANALYSIS OF MINIATURIZED DISK-BEND TEST-RESULTS

The fracture toughness of the intermetallic alloy Ti-46.5Al-2.1Cr-3.0N b-0.2W, heat treated to produce a duplex microstructure, was measured to be 11.93 +/- 2.18 MPa m(1/2) using the miniaturized disk-bend test (MDBT) in conjunction with the controlled-flaw method. The diameter of the specimens in the current experiments was 3 mm, and the thicknesse s ranged from 286 to 344 mu m. This technique utilizes a Vickers inden tation in the center of the tensile face of a disk-shaped specimen tha t is subsequently tested in biaxial bending, and the cracks responsibl e for failure of the specimens must emanate from the corners of the in dentation. Because the alloy deforms plastically prior to failure, fin ite element analysis was performed to determine the fracture stresses of the specimens, using st published flow curve to model its plasticit y. This is the first time a value of fracture toughness exceeding 10 M Pa m(1/2) has been measured using this method, and the value of 11.93 MPa m(1/2) compares well with previously calculated fracture toughness es for similar alloys. (C) 1998 Elsevier Science Limited. All rights r eserved.