EM Characterization of Precipitates in as-Cast and Annealed Ni45.5Ti45.5Nb9 Shape Memory Alloys

2013 ◽  
Vol 738-739 ◽  
pp. 113-117 ◽  
Author(s):  
Hui Shi ◽  
Jan Frenzel ◽  
Dominique Schryvers
Keyword(s):  
Geometric Phase ◽  
Scanning Transmission Electron Microscopy ◽  
Thermal Hysteresis ◽  
Cast Alloy ◽  
Lattice Parameter ◽  
Annealed Alloy ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
The Matrix

Nb-rich precipitates in the matrix of as-cast and annealed Ni45.5Ti45.5Nb9 alloys are investigated by scanning and scanning transmission electron microscopy, including slice-and-view and geometric phase analysis (GPA). The Nb-rich bcc nano-precipitates in the as-cast alloy have a 10% lattice parameter difference with the B2 matrix and reveal compensating interface dislocations. The 3D reconstruction of the configuration of small Nb-rich precipitates in the annealed alloy reveals a wall-like distribution of precipitates, which may increase the thermal hysteresis of the material.

scholarly journals Characterization of crystal structure and precipitation crystallography of a new MgxAl2−xGd phase in an Mg97Al1Gd2alloy

2016 ◽  
Vol 49 (4) ◽  
pp. 1177-1181 ◽  
Author(s):  
X.-F. Gu ◽  
T. Furuhara
Keyword(s):  
Crystal Structure ◽  
Lattice Parameter ◽  
Face Centered Cubic ◽  
Laves Phases ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
The Matrix ◽  
The Face ◽  
Face Centered

The composition, crystal structure and precipitation crystallography of a newly found precipitate are characterized by Cs-corrected scanning transmission electron microscopy. The composition of the plate-like precipitate could be expressed as MgxAl2−xGd (x= 0.38), and its crystal structure is the same as the face-centered cubic type Laves phases Mg2Gd and Al2Gd, with a lattice parameter of 7.92 Å (space group No. 227, Fd\overline 3m). The orientation relationship between the matrix and precipitate is found to be (0001)m//(111)pand [10\overline 10]m//[1\overline 10]p, and the habit plane is parallel to the (0001)m//(111)pplane. In addition, this preferred crystallography of phase transformation is well explained on the basis of the atomic matching at the interface.

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