Mechanical twinning in Ni-based single crystal superalloys during multiaxial creep at 1050 °C

2018 ◽  
Vol 722 ◽  
pp. 76-87 ◽  
Author(s):  
Jean-Briac le Graverend ◽  
Florence Pettinari-Sturmel ◽  
Jonathan Cormier ◽  
Muriel Hantcherli ◽  
Patrick Villechaise ◽  
...  
1978 ◽  
Vol 21 (85) ◽  
pp. 607-620 ◽  
Author(s):  
M. Matsuda ◽  
G. Wakahama

AbstractFor several types of polycrystalline ice of different origins, the spatial lattice orientation of each crystal was determined by measurements of both the a- and c-axis orientations. Analyses of the orientations of adjoining crystals showed that a great majority of adjoining crystals may be in a twinning relation. With special reference to the multi-maximum c-axis preferred-orientation fabric (the so-called “diamond pattern”), which is expected to occupy the largest part of a glacier ice mass, the crystal boundary structure was estimated. The preferred c-axis orientations of this fabric were explained as being the result of coincident oxygen-oxygen lines (hydrogen-bond lines) between adjoining crystals being concentrated in the orientations where seven oxygen-oxygen lines of one single crystal of ice are distributed. From the above result, it was concluded that the multi-maximum fabric is of the polycrystalline structure closest to the structure of a single crystal of ice among all the fabrics found in large ice masses.It is found that the occurrence, in glaciers and ice sheets, of a multi-maximum fabric has a bias to the parts which have undergone a strong shear deformation for a long time. It is thus suggested that plastic deformation of ice with this fabric may be attributed to mechanical twinning due to a strong shear stress.


1997 ◽  
Vol 180 (1) ◽  
pp. 101-104 ◽  
Author(s):  
Bong Mo Park ◽  
Kenji Kitamura ◽  
Kazuya Terabe ◽  
Yasunori Furukawa ◽  
Yangyang Ji ◽  
...  

1978 ◽  
Vol 21 (85) ◽  
pp. 607-620 ◽  
Author(s):  
M. Matsuda ◽  
G. Wakahama

Abstract For several types of polycrystalline ice of different origins, the spatial lattice orientation of each crystal was determined by measurements of both the a- and c-axis orientations. Analyses of the orientations of adjoining crystals showed that a great majority of adjoining crystals may be in a twinning relation. With special reference to the multi-maximum c-axis preferred-orientation fabric (the so-called “diamond pattern”), which is expected to occupy the largest part of a glacier ice mass, the crystal boundary structure was estimated. The preferred c-axis orientations of this fabric were explained as being the result of coincident oxygen-oxygen lines (hydrogen-bond lines) between adjoining crystals being concentrated in the orientations where seven oxygen-oxygen lines of one single crystal of ice are distributed. From the above result, it was concluded that the multi-maximum fabric is of the polycrystalline structure closest to the structure of a single crystal of ice among all the fabrics found in large ice masses. It is found that the occurrence, in glaciers and ice sheets, of a multi-maximum fabric has a bias to the parts which have undergone a strong shear deformation for a long time. It is thus suggested that plastic deformation of ice with this fabric may be attributed to mechanical twinning due to a strong shear stress.


2003 ◽  
Vol 426-432 ◽  
pp. 797-802 ◽  
Author(s):  
M.G. Ardakani ◽  
H. Basoalto ◽  
B.A. Shollock ◽  
Malcolm McLean

2011 ◽  
Vol 674 ◽  
pp. 61-69
Author(s):  
Małgorzata Perek-Nowak ◽  
Marek S. Szczerba

In the paper the concept of structure refinement due to mechanical twinning is discussed. It is postulated that the process of structure refinement may occur when dominant crystal shear proceeds across twin-matrix interface (Mode 2). Contrary, if the crystal shear proceeds parallel to the interface (Mode 1) no condition for structure refinement is satisfied. The conditions of the structure refinement and no structure refinement are shown taking example of tensile Cu-8%at. Al single crystals of two orientations [1 4 5] and [1 1 2] tested in liquid nitrogen. The tensile characteristics are therefore divided into stages associated with the Mode 1 and Mode 2, which correspond to the fact whether refinement of single crystal structure is present or not, as it is proved by the EBSD analysis. The performed analysis showed that structure refinement consists of formation of regions of new orientations, where the most common feature is the II order twinning (the case [1 4 5]) supported by other regions of specific orientations necessary to accommodate mainly the transfer of crystal twin shear across the twin-matrix interface. Moreover, if the II order twinning plays the dominating function (the case [1 1 2]) higher order twins are to bring into operation to assure further ductility of a deformed sample.


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