Study of fatigue crack growth behavior of cold worked and aged TiNbSn alloys

Abstract

Titanium alloys are used in several engineering fields. TiNbSn alloys have advantages with respect to mechanical properties, if compared to other titanium alloys. Cold worked TiNbSn alloys can undergoes elastic modulus less than half of the modulus of Ti6Al4V alloy, for example. The study aims to investigate the fatigue crack growth behavior (da/dN x ΔK) of cold worked and aged TiNbSn alloys according to the niobium (Nb) and tin (Sn) contents and heat treatment. Cold-rolled Ti35Nb2Sn, Ti42Nb2Sn and Ti42Nb alloys were manufactured with 55% engineering thickness reduction and aged at 400°C for 48 hours. The 42% Nb content and aging heat treatment enhanced the crack growth behavior as in the Paris regime as in the crack growth threshold (Kth), which was attributed to the crack tortuosity exhibited by the alloys. The tortuosity leads to the roughness induced crack closure effect. The Kth increased with the aging due to the α precipitation in the β grains.