TEMPERATURE-INDUCED SHAPE MEMORY IN POLYCRYSTALLINE URANIUM-BASE NIOBIUM ALLOYS: CHARACTERIZATION.

An x-ray diffraction study of the reversible deformation inodes associated with the shape memory effect has been carried out on a series of uranium-niobium alloys near the monotectoid composition (6.2 wt. % Nb). Diffraction patterns were measured as a function of strain, in situ, while the specimens were under stress as part of an attempt to explain the “easy-flow”, low-strain plateau in the stress-strain curve. The alloys, consisting of highly twinned, metastable α” (monoclinic) and γ° (tetragonal) phases derived from the high-temperature BCC γ phase, produced broad, overlapping diffraction lines difficult to analyze by conventional techniques. One solution to this problem was to use a segmented step-scan technique so as to apportion the scan time to concentrate on the most difficult regions. This paper discusses data obtained from an α” alloy and a dual-phase α” + γ° alloy.

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A phenomenological study of the shape memory effect in polycrystalline uranium-niobium alloys

Metallurgical Transactions A ◽

10.1007/bf02648337 ◽

1981 ◽

Vol 12 (5) ◽

pp. 733-741 ◽

Cited By ~ 53

Author(s):

R. A. Vandermeer ◽

J. C. Ogle ◽

W. G. Northcutt

Keyword(s):

Shape Memory ◽

Shape Memory Effect ◽

Memory Effect ◽

Phenomenological Study ◽

Niobium Alloys

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Examination of temperature-induced shape memory of uranium--5. 3-to 6. 9 weight percent niobium alloys

10.2172/7335910 ◽

1976 ◽

Cited By ~ 1

Author(s):

V. C. Hemperly

Keyword(s):

Shape Memory ◽

Weight Percent ◽

Niobium Alloys ◽

Percent Niobium

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Tensile Failure of 55-Nitinol Wire

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100113858 ◽

1975 ◽

Vol 33 ◽

pp. 46-47

Author(s):

F. I. Grace

Keyword(s):

Shape Memory ◽

Shape Memory Effect ◽

Memory Effect ◽

Stoichiometric Composition ◽

Tensile Failure ◽

Initial State ◽

Initial Shape ◽

Nitinol Wire ◽

Cscl Type ◽

Shear Transformation

An interest in NiTi alloys with near stoichiometric composition (55 NiTi) has intensified since they were found to exhibit a unique mechanical shape memory effect at the Naval Ordnance Laboratory some twelve years ago (thus refered to as NITINOL alloys). Since then, the microstructural mechanisms associated with the shape memory effect have been investigated and several interesting engineering applications have appeared.The shape memory effect implies that the alloy deformed from an initial shape will spontaneously return to that initial state upon heating. This behavior is reported to be related to a diffusionless shear transformation which takes place between similar but slightly different CsCl type structures.

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TEM study of order, structure and defects of β and martensite in Cu-Al-Mn shape memory alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100174072 ◽

1990 ◽

Vol 48 (4) ◽

pp. 188-189

Author(s):

J.M. Guilemany ◽

F. Peregrin

Keyword(s):

Shape Memory ◽

Orthophosphoric Acid ◽

Isopropyl Alcohol ◽

Metastable Phase ◽

Characteristic Temperature ◽

Ethanol Solution ◽

Order Structure ◽

Thin Foils ◽

Polycrystalline Alloys ◽

Diamond Saw

The shape memory effect (SME) shown by Cu-Al-Mn alloys stems from the thermoelastic martensitic transformation occuring between a β (L2,) metastable phase and a martensitic phase. The TEM study of both phases in single and polycrystalline Cu-Al-Mn alloys give us greater knowledge of the structure, order and defects.The alloys were obtained by vacuum melting of Cu, Al and Mn and single crystals were obtained from polycrystalline alloys using a modified Bridgman method. Four different alloys were used with (e/a) ranging from 1.41 to 1.46 . Two different heat treatments were used and the alloys also underwent thermal cycling throughout their characteristic temperature range -Ms, Mf, As, Af-. The specimens were cut using a low speed diamond saw and discs were mechanically thinned to 100 μm and then ion milled to perforation at 4 kV. Some thin foils were also prepared by twin-jet electropolishing, using a (1:10:50:50) urea: isopropyl alcohol: orthophosphoric acid: ethanol solution at 20°C. The foils were examinated on a TEM operated at 200 kV.

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