FRACTURE-TOUGHNESS TESTS FOR TITANIUM ALLOY PLATE AND FORGINGS
Abstract:
The notch fracture-toughness characteristics of titanium alloy plate are being investigated to provide alloy selection design and specification criteria for the use of titanium alloys as hull materials for deep-diving submarines and for other structural applications. Although the Navys primary interest is in 120-ksi yield strength alpha or near-alpha titanium alloys, the entire spectrum of titanium alloys is under study. The results obtained from laboratory fracture-toughness tests, such as the Charpy V-notch test C sub v and the newly developed NRL drop-weight tear test DWTT, are correlated with explosion tear test ETT results. The explosion tear test is a simulated submarine-hull structural prototype test in which the metal is explosion loaded to establish its plastic deformation capability in the presence of a crack-like flaw. Variations in notch fracture-toughness associated with alloy composition and interstitial level, processing, heat treatment, microstructure, and weld deposits were evaluated and assessed with the various fracture-toughness tests. The results of these studies show that it is possible to predict the expected structural performance of the titanium plate and forgings from the DWTT energy values through the correlation with the ETT. The relationships of the C sub v test and the DWTT have been established for these materials.