Microstructure and plastic deformation of orthorhombic titanium aluminides Ti2AlNb. IV. Formation of the transformation twins upon the α2 → O phase transformation

2007 ◽  
Vol 103 (4) ◽  
pp. 388-394 ◽  
Author(s):  
N. V. Kazantseva ◽  
S. L. Demakov ◽  
A. A. Popov
Keyword(s):  
Plastic Deformation ◽  
Phase Transformation ◽  
Titanium Aluminides ◽  
Transformation Twins ◽  
Orthorhombic Titanium ◽  
O Phase

Phase Transformation in Orthorhombic Ti2AlNb Alloys Under Severe Deformation

2004 ◽  
Vol 842 ◽  
Author(s):  
B. A. Greenberg ◽  
N. V. Kazantseva ◽  
V. P. Pilugin
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Phase Structure ◽  
Titanium Aluminides ◽  
Equilibrium Phase ◽  
Severe Deformation ◽  
Disordered Phase ◽  
Titanium Aluminum ◽  
B2 Phase ◽  
O Phase

ABSTRACTIt was found that severe plastic deformation of orthorhombic alloys caused phase transformations of the displacement type and those associated with a change in the degree of long-range order, namely B2→ω(B82 ), B2→B19 and B2→β (BCC) (in the case of alloy with initial B2-phase structure) and O→B19→A20 (initial O-phase structure, Ti2AlNb). Unlike to ordinary metals, severe plastic deformation of the titanium aluminum intermetallics leads to decreasing of the strength of the material. The B19 and A20 phases are metastable. They are absent in the equilibrium phase diagrams of the compounds under investigation. The formation of the disordered phase states with extensive sliding and having great plasticity under severe deformation makes possible to consider severe deformation as the way for increasing of plasticity of the titanium aluminides.

Magnetic Characterization of SUS316L Deformed by High Pressure Torsion

2011 ◽  
Vol 239-242 ◽  
pp. 1300-1303
Author(s):  
Hong Cai Wang ◽  
Minoru Umemoto ◽  
Innocent Shuro ◽  
Yoshikazu Todaka ◽  
Ho Hung Kuo
Keyword(s):  
Plastic Deformation ◽  
High Pressure ◽  
Stainless Steel ◽  
Phase Transformation ◽  
Austenitic Stainless Steel ◽  
Volume Fraction ◽  
High Pressure Torsion ◽  
Austenitic Matrix ◽  
Magnetic Characterization

SUS316L austenitic stainless steel was subjected to severe plastic deformation (SPD) by the method of high pressure torsion (HPT). From a fully austenitic matrix (γ), HPT resulted in phase transformation from g®a¢. The largest volume fraction of 70% a¢ was obtained at 0.2 revolutions per minute (rpm) while was limited to 3% at 5rpm. Pre-straining of g by HPT at 5rpm decreases the volume fraction of a¢ obtained by HPT at 0.2rpm. By HPT at 5rpm, a¢®g reverse transformation was observed for a¢ produced by HPT at 0.2rpm.

Severe plastic deformation and hydrogenation of the titanium aluminides

2011 ◽  
Vol 509 (38) ◽  
pp. 9307-9311 ◽  
Author(s):  
N.V. Kazantseva ◽  
N.V. Mushnikov ◽  
A.G. Popov ◽  
P.B. Terent’ev ◽  
V.P. Pilyugin
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Titanium Aluminides

Phase Transformations of the Ti-40% Nb Alloy Under External Influence

2016 ◽  
Vol 683 ◽  
pp. 174-180 ◽  
Author(s):  
Yuri P. Sharkeev ◽  
Zhanna G. Kovalevskaya ◽  
Margarita A. Khimich ◽  
Vladimir A. Bataev ◽  
Qi Fang Zhu ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Phase Transformation ◽  
Severe Plastic Deformation ◽  
Phase Transformations ◽  
Optical Metallography ◽  
External Influence ◽  
Β Phase ◽  
Α Phase ◽  
Pressing Operation ◽  
Loading Axis

The phase transformations of the alloy Ti-40 mas % Nb after tempering and severe plastic deformation are studied. The phase transformations of the alloy according to the type and conditions of external influences are analyzed using methods of XRD, SEM and optical metallography. It is determined that inverse phase transformation of the metastable α''-phase to equilibrium β-phase is carried out after severe plastic deformation. Complete phase transformation α'' → β is typical for the mode, which consists of three pressing operation with the change of the loading axis in cramped conditions, followed by a multi-pass rolling in grooved rolls.

Elemental Segregation and O-Phase Formation in a Gamma-TiAl Alloy

2018 ◽  
Vol 941 ◽  
pp. 741-746 ◽  
Author(s):  
Heike Gabrisch ◽  
Tobias Krekeler ◽  
Uwe Lorenz ◽  
Marcus Willi Rackel ◽  
Martin Ritter ◽  
...  
Keyword(s):  
Tial Alloy ◽  
Titanium Aluminides ◽  
Orthorhombic Phase ◽  
Aircraft Engines ◽  
Duplex Microstructure ◽  
Two Phase ◽  
Chemical Homogeneity ◽  
Phase Form ◽  
Tial Alloys ◽  
O Phase

Titanium aluminides based on the L10 ordered g-phase are promising structural light-weight materials for applications in aircraft engines. Typical compositions for γ-TiAl alloys lie in the range Ti-(44-48)Al (at.-%). For high creep resistance, a two-phase microstructure based on lamellar (α2+γ)-colonies is desirable that may be tuned towards better ductility by introducing pure γ-grains (near lamellar or duplex microstructure).γ-TiAl alloys are often alloyed with niobium for increased oxidation resistance and improved mechanical properties. HEXRD and TEM studies of the alloy Ti-42Al-8.5Nb revealed that the orthorhombic O-phase forms during annealing at 500-650°C. This orthorhombic phase has been known in Nb-rich, Al-lean, α2-based Ti-aluminides since the late 1980ies (Nb> 12.5 at.-%, Al< 31 at.-%) but the finding in γ-based alloys is new.TEM imaging showed that the O-phase is located within α2 lamellae of lamellar (α2+γ)-colonies. O-phase domains and α2 phase form small columnar crystallites based in the α2/γ interface. The columnar crystallites grow parallel to the [0001] direction of the α2 phase and appear as facets when observed along this direction. The evolution of domains and facets with annealing time and the chemical homogeneity of the phases are investigated.The results of STEM imaging show that O-phase domains form during annealing at 550 °C for 8hours or 168 hours. After 168 hours of annealing Nb segregations are observed by EDX mapping within O-phase domains. In comparison, no segregation of niobium is detected after 8 hours of annealing.

Sign in / Sign up

Export Citation Format

Share Document