AN INVESTIGATION OF THE CRACK-PROPAGATION RESISTANCE OF HIGH-STRENGTH ALLOYS AND HEAT-RESISTANT ALLOYS. Summary Technical Report, December 23, 1960 through October 23, 1962

Technical Report · Wed Nov 21 04:00:00 EST 1962

OSTI ID:4153505

Morrison, J D; Jenkins, P C; Kattus, J R

The purpose of this program was to determine the crackpropagation resistance of super-alloy andd refractory-metal sheet materials and to investigate certain aspects of the elevated-temperature mechanical behavior of high-strength low-alloy steels. Sheet specimens containing central transverse fatigue cracks were used in the experimental work. It was found that the fracture toughness of the nickel-base alloys ---Rene' 41, Nimonic 90, Inconel-X, and Unitemp 1753 ---decreased slightly in the temperature range from about 1000 to 1400 deg F, in which temperature range there were generally increases in ultimate tensile strength and decreases in tensile elongition. The alloys A286 (ironbase) and L605 (cobalt-base) did not show this brittleness tendency. Among the refractory metals, unalloyed molybdenum was found to have a brittle-ductile transition temperature of about 150 deg F; the molybdenum alloys --- Mo-1/2%Ti and TZM---both had transition temperatures of about 65 deg F. Unalloyed tungsten sheet, containing sharp notches rather than fatigue cracks, showed an increasing tendency to brittleness below about 500 deg F. Two columbium-base alloys---D-14 and FS82---were ductile over the temperature range investigated---from -320 deg F to about 1000 deg F. In an investigation of apparent strain-aging effects in steels, it was found that greatly increasing the rate of loading diminished the net-fracture-stress minimum that occurs at around 300 deg F at slow loading rates. The program also included an evaluation of the compliance gage, originally developed at the U. S. Naval Research Laboratory, for the determination of critical crack length. It was found that, by means of this device, critical crack length can be reproducibly measured in crack-propagation tests over a wide temperature range. Used with certain types of crackpropagation specimens, such as the shear-cracked specimen, the gage apparently gives a reliable measure of the plane-strain fracture-toughness parameters, K/sub Ic/ and G/sub Ic/. (auth)

• Research Organization: Southern Research Inst., Birmingham, Ala
• NSA Number: NSA-18-005769
• OSTI ID: 4153505
• Report Number(s): AD-290278
• Country of Publication: United States
• Language: English

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METALS, CERAMICS, AND OTHER MATERIALS