EFFECT OF OUTDOOR EXPOSURE AT AMBIENT AND ELEVATED TEMPERATURES ON FATIGUE LIFE OF Ti-6A1-4V TITANIUM ALLOY SHEET IN THE ANNEALED AND THE SOLUTION-TREATED AND AGED CONDITION

摘要

Specimens of Ti-6A1-4V titanium alloy sheet in the annealed and the solution-treated and aged heat-treatment condition were exposed outdoors at ambient and 560 K (550℉) tempera¬tures to determine the effect of outdoor exposure on fatigue life. Effects of exposure were determined by comparing fatigue lives of exposed specimens to those of unexposed specimens. Two procedures for fatigue testing the exposed specimens were evaluated: (1) fatigue tests conducted outdoors by applying 1200 load cycles per week until failure occurred and (2) conven¬tional fatigue tests (continuous cycling until failure occurred) conducted indoors after outdoor exposure under static load. The exposure period ranged from 9 to 28 months for the outdoor fatigue-test group and was 24 months for the static-load group. All fatigue tests were constant-amplitude bending of specimens containing a drilled hole (stress concentration factor of 1.6).