Fatigue Properties of Titanium Alloys in Liquid Helium

Abstract

Titanium alloys have nonmagnetic and high strength properties as well as low density. These excellent characteristics are expected to make the alloys candidates for structural materials of cryogenic systems including superconducting machineries. We have been studying on mechanical properties of titanium alloys at cryogenic temperatures. Fatigue tests were carried out for Ti-5Al-2.5Sn and Ti-6Al-4V alloys, both of which had high fracture toughness at low temperatures. Fatigue crack initiation started at the inside of the specimens when tested at lower temperatures and under higher cycles. Neither macroscopic nor microscopic defects were observed at the crack initiation sites.