Strengthening of Cr?Ni steels with unstable austenite

1973 ◽  
Vol 15 (4) ◽  
pp. 271-277
Author(s):  
V. B. Spiridonov ◽  
L. N. Kuz'minskaya ◽  
Yu. P. Gordeev
Keyword(s):  
Unstable Austenite

Fatigue Life Curves of NiTi Alloys – The Z Effect

2010 ◽  
Vol 643 ◽  
pp. 69-77 ◽  
Author(s):  
Ana Maria Gontijo Figueiredo ◽  
Berenice Mendonça Gonzalez ◽  
Vicente Tadeu Lopes Buono ◽  
Paulo José Modenesi
Keyword(s):  
Fatigue Life ◽  
High Strain ◽  
Rotation Speed ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Large Strains ◽  
Unusual Behavior ◽  
Niti Alloys ◽  
Stable Austenite ◽  
Unstable Austenite

Superelasticity is closely related to shape memory effect. It refers to the property presented by some materials submitted to large strains (usually up to about 8%) to restore their original shape immediately after unloading without the need of heating. This phenomenon results directly from a diffusionless transformation of the material from an austenitic to a martensitic phase (martensitic transformation). The recovering mechanism is the reverse transformation, from martensite to austenite. This paper compares fatigue live curves obtained in bending-rotation fatigue tests carried out on wires of NiTi alloys with three different microstructures, stable austenite, unstable austenite (superelastic), and stable martensite. These curves are also compared to data from the literature. The tests were strain controlled and the wires were submitted to strain amplitudes from 0.6% to 12.0%. To minimize changes in material properties, the wire temperature was monitored using a thermocouple and controlled by its rotation speed. For strain amplitudes up to 4%, the εa-Nf curve for superelastic wires was consistent with those reported in the literature, closely approaching the curve of the stable austenite wire. For higher strain amplitudes, fatigue life of superelastic wires increased with strain until it approached the fatigue life curve of stable martensitic wire. This unusual behavior results in a “Z-shaped” curve for high strain values. It is possibly linked to the changes in microstructure and fatigue properties that occur when the superelastic material is deformed.

Mechanism of FIB-Induced Phase Transformation in Austenitic Steel

2021 ◽  
pp. 1-13
Author(s):  
Joseph R. Michael ◽  
Lucille A. Giannuzzi ◽  
M. Grace Burke ◽  
Xiang Li Zhong
Keyword(s):  
Ion Irradiation ◽  
Ion Beam ◽  
Transformation Product ◽  
304 Stainless Steel ◽  
Orientation Relationships ◽  
Austenite Grain ◽  
Beam Sample ◽  
Bcc Phase ◽  
Ion Species ◽  
Unstable Austenite

The transformation of unstable austenite to ferrite or α′ martensite as a result of exposure to Xe+ or Ga+ ions at room temperature was studied in a 304 stainless steel casting alloy. Controlled Xe+ and Ga+ ion beam exposures of the 304 were carried out at a variety of beam/sample geometries. It was found that both Ga+ and Xe+ ion irradiation resulted in the transformation of the austenite to either ferrite or α′ martensite. In this paper, we will refer to the transformation product as a BCC phase. The crystallographic orientation of the transformed area was controlled by the orientation of the austenite grain and was consistent with either the Nishiyama–Wasserman or the Kurdjumov–Sachs orientation relationships. On the basis of the Xe+ and Ga+ ion beam exposures, the transformation is not controlled by the chemical stabilization of the BCC phase by the ion species, but is a result of the disorder caused by the ion-induced recoil motion and subsequent return of the disordered region to a more energetically favorable phase.

Influence of heat treatment on the structure and mechanical properties of chrome steel with unstable austenite

2017 ◽  
Vol 47 (5) ◽  
pp. 299-303
Author(s):  
M. Yu. Belomyttsev ◽  
D. A. Kozlov ◽  
E. I. Kuz’ko ◽  
A. V. Molyarov ◽  
T. N. Nosirov
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Chrome Steel ◽  
Unstable Austenite

Mechanical properties of carbon chromium-manganese steels with a structure of unstable austenite

1986 ◽  
Vol 18 (12) ◽  
pp. 1639-1644
Author(s):  
M. A. Filippov ◽  
M. E. Poptsov ◽  
V. E. Lugovykh
Keyword(s):  
Mechanical Properties ◽  
Unstable Austenite ◽  
Manganese Steels

Features of unstable austenite steels

1972 ◽  
Vol 14 (9) ◽  
pp. 788-792
Author(s):  
I. N. Bogachev ◽  
T. D. �ismondt
Keyword(s):  
Unstable Austenite
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