Accession Number:
AD0628277
Title:
FRACTOGRAPHIC ANALYSIS OF TI-7AL-2CB-1TA AND TI-6AL-4V FRACTURES DEVELOPED IN 'WET' FATIGUE.
Descriptive Note:
Interim rept.,
Corporate Author:
NAVAL RESEARCH LAB WASHINGTON D C
Personal Author(s):
Report Date:
1966-01-14
Pagination or Media Count:
20.0
Abstract:
Crack-growth-rate studies on Ti-7Al-2Cb-1Ta and Ti-6Al-4V alloys in low-cycle fatigue were performed in air and in a 3.5-percent salt-water solution. The Ti-7Al-2Cb-1Ta alloy was additionally tested in distilled water. An increase in crack-growth rate at all strain ranges was observed for the Ti-7Al-2Cb-1Ta in the wet environments over that in the dry, whereas the Ti-6Al-4V alloys did not appear to be sensitive to a wet environment. At a strain range of 8000 to 9000 microinchesinch, corresponding to about 60-percent yield strength, the crack-growth rate of Ti-7Al-2Cb-1Ta alloy accelerated and became erratic. Fractographic studies show that the increase in crack-growth rate is due to a change from the ductile mode of fatigue fracture usually found in dry low-cycle fatigue tests of titanium alloys, to the brittle quasi-cleavage mode of fracture-a fracture mechanism of stress-corrosion cracking. The amount of quasi-cleavage seen on the fatigued fracture surface generally corresponds to the crack-growth-rate increase thus, it is indicative of the degree of stress-corrosion cracking sensitivity. Author
Descriptors:
Subject Categories:
- Properties of Metals and Alloys