Low temperature mechanical properties of titanium and weld joints (T[lc]i/T[lc]i, T[lc]i/N[lc]b) for helium vessels

Abstract

The joint project for high-intensity proton accelerators in KEK and JAERI has been proposed with the superconducting (SC) proton linac. Mechanical properties of commercially pure titanium (Ti) and weld (EB (Electron Beam) and TIG) joints were tested at 4 K in order to verify a possibility of usage of titanium to a helium vessel material of a 400 to 600 MeV SC linac. Tensile tests, Charpy impact tests, bending tests and fracture toughness tests were conducted at room temperature (RT), 77 K and 4 K mainly for the JIS Class 2 commercially pure titanium (0.1 to 0.12 percent oxygen) and weld joints (Ti/Ti, Ti/Nb (niobium)). Typical data of the fracture toughness at 4 K were 66 Mpa m(sup 1/2) (KIC(J)) for JIS Class2 Ti base metal, 210 Mpa m(sup 1/2) (KQ(J)) for Ti/Ti EB weld and 87 Mpa m(sup 1/2) (KIC(J)) for Ti/Nb EB weld.