The fatigue crack propagation behaviour of two titanium alloys,types Ti6246 and Ti6242,has been investigated at temperatures ranging from room temperature up to 500 deg C.To get a better understanding of the effect of environment,tests were performed in air and high vacuum.This paper deals with an in-depth analysis of the shielding effect of crack closure with respect to the alloys' microstructure and environment.Substantial interaction is shown between closure and environment,especially in the near threshold region,and the repective influence of crack surface oxidation and water vapour embrittlement is discussed.
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