Observations on Delayed Cracking in Welded Structures of Unalloyed Titanium Sheet
Observations on Delayed Cracking in Welded Structures of Unalloyed Titanium Sheet

Author: R. H. Ernst

Publisher:

Published: 1964

Total Pages: 12

ISBN-13:

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A brief study of delayed fracture in a seam-welded titanium panel is summarized in this memorandum. Examination of the fracture surface with electron microscopy showed that the material cleaved, failing in a brittle manner. Although the nature of the embrittlement was not clearly defined, titanium hydride phase was suspected as a prime contributor to failure. Even though the hydrogen content of the titanium was only 65 ppm, hydride embrittlement was thought to have occurred from precipitation of hydride platelets on crystal planes oriented normal to welding stresses. Other work, briefly discussed in the memorandum, has confirmed that hydride platelets in titanium can be oriented by stress and that tensile ductility of Zircaloy (which behaves similarly with respect to hydrogen, to titanium) depends upon hydride orientation. Stress-relief annealing of welded titanium structures is recommended wherever possible to minimize embrittlement by stress-oriented hydrides. (Author).

Recent Developments in Welding Thick Titanium Plate
Recent Developments in Welding Thick Titanium Plate

Author: R. E. Monroe

Publisher:

Published: 1965

Total Pages: 26

ISBN-13:

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This memorandum represents a combined effort by the U.S. Naval Applied Science Laboratory, Brooklyn, New York, and the Defense Metals Information Center to summarize new information on welding thick Ti plate. Thick plate of Ti continues to be of interest to the aerospace and defense industries for possible use in submersibles, armored vehicles, large space boosters, high-speed aircraft, and for pressure vessels. This memorandum generally is limited to information on welding Ti plate that is (1) at least 1 in. thick and (2) that is not covered by DMIC Report 185, The Status and Properties of Titanium Alloys for Thick Plate, June 14, 1963. The general requirements for welding Ti are not repeated here, since they are well documented in references mentioned in the inroduction to the memorandum. Sections have been prepared to cover material developments, welding-process developments, weld properties, and residual welding stresses. (Author).

Porosity in Titanium Welds
Porosity in Titanium Welds

Author: Robert Melvin Evans

Publisher:

Published: 1964

Total Pages: 14

ISBN-13:

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Porosity in fusion welds in titanium has been encountered to some extent in all programs using this joining method. While measures to control cleanliness and to employ good welding techniques have successfully reduced the occurrence of porosity, specific indentification of the various causes of porosity is still lacking. Some factors suspected of causing porosity in titanium welds are hydrogen, cleanliness of joint area, contamination in filler wire, and welding procedures and techniques.

Investigation of Delayed-cracking Phenomenon in Hydrogenated Unalloyed Titanium
Investigation of Delayed-cracking Phenomenon in Hydrogenated Unalloyed Titanium

Author: R. A. Wood

Publisher:

Published: 1961

Total Pages: 22

ISBN-13:

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Three grades of unalloyed titanium were studied to determine the effect of variations in O and N contents on delayed cracking. The bar stock was analyzed for interstitial content, then vacuum annealed to remove most of the H. Large samples of the 1/2-in.-diam vaccum-annealed stock were subsequently hydrogenated to about 90 and 160 ppm H levels. Hydrogen-induced strainaging embrittlement at ambient temperatures in interstitial-containing alphi Ti was not indicated by the results of stress-rupture tests. The results indicate that strain-aging embrittlement does not occur in unalloyed Ti having up to 0.38 wt-% O with as much as 160 ppm H content. However, a noticable effect of H on notch sensitivity of the materials, in the alpha-annealed and especially in the beta-annealed conditions, was observed. It appears probable that H was concentrated in the critical areas by a thermaldiffusion process to create an ultrasensitive zone. Failure might have occurred subsequently as a result of simple overstressing, or by accidentally applied impact stresses, or by a more complicated low-cycle fatigue mechanism. (Author).