Download or read book Characterization of Dislocation Structures and Deformation Mechanisms in As grown and Deformed Directionally Solidified NiAl Mo Composites written by and published by . This book was released on 2015 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this paper, directionally solidified (DS) NiAl-Mo eutectic composites were strained to plastic strain values ranging from 0% to 12% to investigate the origin of the previously observed stochastic versus deterministic mechanical behaviors of Mo-alloy micropillars in terms of the development of dislocation structures at different pre-strain levels. The DS composites consist of long, [1 0 0] single-crystal Mo-alloy fibers with approximately square cross-sections embedded in a [1 0 0] single-crystal NiAl matrix. Scanning transmission electron microscopy (STEM) and computational stress state analysis were conducted for the current study. STEM of the as-grown samples (without pre-straining) reveal no dislocations in the investigated Mo-alloy fibers. In the NiAl matrix, on the other hand, a(1 0 0)-type dislocations exist in two orthogonal orientations: along the [1 0 0] Mo fiber axis, and wrapped around the fiber axis. They presumably form to accommodate the different thermal contractions of the two phases during cool down after eutectic solidification. At intermediate pre-strain levels (4-8%), a/2(1 1 1)-type dislocations are present in the Mo-alloy fibers and the pre-existing dislocations in the NiAl matrix seem to be swept toward the interphase boundary. Some of the dislocations in the Mo-alloy fibers appear to be transformed from a(1 0 0)-type dislocations present in the NiAl matrix. Subsequently, the transformed dislocations in the fibers propagate through the NiAl matrix as a(1 1 1) dislocations and aid in initiating additional slip bands in adjacent fibers. Thereafter, co-deformation presumably occurs by (1 1 1) slip in both phases. With a further increase in the pre-strain level (>10%), multiple a/2(1 1 1)-type dislocations are observed in many locations in the Mo-alloy fibers. Interactions between these systems upon subsequent deformation could lead to stable junctions and persistent dislocation sources. Finally, the transition from stochastic to deterministic, bulk-like behavior in sub-micron Mo-alloy pillars may therefore be related to an increasing number of multiple a(1 1 1) dislocation systems within the Mo fibers with increasing pre-strain, considering that the bulk-like behavior is governed by the forest hardening of these junctions.
Download or read book Characterization of Dislocation Structures and Deformation Mechanisms in As grown and Deformed Directionally Solidified NiAl u2013 Mo Composites written by and published by . This book was released on 2015 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this paper, directionally solidified (DS) NiAl–Mo eutectic composites were strained to plastic strain values ranging from 0% to 12% to investigate the origin of the previously observed stochastic versus deterministic mechanical behaviors of Mo-alloy micropillars in terms of the development of dislocation structures at different pre-strain levels. The DS composites consist of long, [1 0 0] single-crystal Mo-alloy fibers with approximately square cross-sections embedded in a [1 0 0] single-crystal NiAl matrix. Scanning transmission electron microscopy (STEM) and computational stress state analysis were conducted for the current study. STEM of the as-grown samples (without pre-straining) reveal no dislocations in the investigated Mo-alloy fibers. In the NiAl matrix, on the other hand, a(1 0 0)-type dislocations exist in two orthogonal orientations: along the [1 0 0] Mo fiber axis, and wrapped around the fiber axis. They presumably form to accommodate the different thermal contractions of the two phases during cool down after eutectic solidification. At intermediate pre-strain levels (4–8%), a/2(1 1 1)-type dislocations are present in the Mo-alloy fibers and the pre-existing dislocations in the NiAl matrix seem to be swept toward the interphase boundary. Some of the dislocations in the Mo-alloy fibers appear to be transformed from a(1 0 0)-type dislocations present in the NiAl matrix. Subsequently, the transformed dislocations in the fibers propagate through the NiAl matrix as a(1 1 1) dislocations and aid in initiating additional slip bands in adjacent fibers. Thereafter, co-deformation presumably occurs by (1 1 1) slip in both phases. With a further increase in the pre-strain level (>10%), multiple a/2(1 1 1)-type dislocations are observed in many locations in the Mo-alloy fibers. Interactions between these systems upon subsequent deformation could lead to stable junctions and persistent dislocation sources. Finally, the transition from stochastic to deterministic, bulk-like behavior in sub-micron Mo-alloy pillars may therefore be related to an increasing number of multiple a(1 1 1) dislocation systems within the Mo fibers with increasing pre-strain, considering that the bulk-like behavior is governed by the forest hardening of these junctions.
Download or read book Micromechanical study on the deformation behaviour of directionally solidified NiAl Cr eutectic composites written by Kumar, Amritesh and published by KIT Scientific Publishing. This book was released on 2017-11-06 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Finite element simulation of dislocation based plasticity and diffusion in multiphase materials at high temperature written by Albiez, Jürgen and published by KIT Scientific Publishing. This book was released on 2019-05-22 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt: A single-crystal plasticity model as well as a gradient crystal plasticity model are used to describe the creep behavior of directionally solidi?ed NiAl based eutectic alloys. To consider the transition from theoretical to bulk strength, a hardening model was introduced to describe the strength of the reinforcing phases. Moreover, to account for microstructural changes due to material ?ux, a coupled diffusional-mechanical simulation model was introduced.
Download or read book Chemical Abstracts written by and published by . This book was released on 2002 with total page 2018 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effect of Microstructure on Creep in Directionally Solidified NiAl 31Cr 3Mo written by and published by . This book was released on 2001 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Metals Abstracts written by and published by . This book was released on 1998 with total page 1042 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Processing and Mechanical Properties of NiAl based In situ Composites written by David Ray Johnson and published by . This book was released on 1994 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1998 with total page 980 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book High Temperature Aluminides and Intermetallics written by S.H. Whang and published by Elsevier. This book was released on 2013-10-22 with total page 759 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume of proceedings is concerned with an increasingly important area, that of intermetallics and high temperature aluminides, which has recently been attracting a great deal of attention. Nearly 150 papers presented at the meeting held in San Diego in September 1991 are reproduced here. They cover a wide range of related topics such as the bonding characteristic and alloying behaviour of TiA1 intermetallic compounds and the cleavage fracture of ordered intermetallic alloys. All the papers have been reviewed according to the standards set by Materials Science and Engineering. This book will be of interest to metallurgists and materials scientists working with composites who are interested in the latest developments in this fast–moving field.
Download or read book Physics Briefs written by and published by . This book was released on 1994 with total page 1256 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Science Abstracts written by and published by . This book was released on 1992 with total page 1228 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Microstructure and Fatigue Behavior of In situ Directionally Solidified NiAl Cr Mo Eutectic Composite written by Kirk Beng-Tek Cheng and published by . This book was released on 1996 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Microstructure Plastic Deformation and Mechanical Properties of Mechanically Alloyed NiAl and NiAl Based Alloys written by Marek Dollar and published by . This book was released on 1991 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nickel aluminide (NiAl) and NiAl based alloys have been produced by mechanical alloys (MA) and hot extrusion, resulting in material which was fully dense, with a homogeneous, bimodal distribution of oxide paricles and with a fine grain size of less than 1 micrometers. Mechanical properties of the MA alloys have been studied by compression testing from room temperature to 1300 K in air. Yield strengths ranged from 1453 MPa to 32 MPa depending on material and test temperature. The MA materials showed a considerable compressive ductility at room temperature (greater than 11.5%) without any microcracking being observed. A ductility minimum was observed at 800K in all MA materials which is deduced to be due to dynamic strain aging. The effects of microstructure on the mechanical properties are discussed. Transmission electron microscopy has been carried out in order to characterize deformation mechanisms. 001 slip was found to be predominant but a strong evidence of 011 slip was also gathered. The occurrence of 001 and 011 slip vectors satisfies general requirement for plasticity and explains significant room temperature ductility of MA NiAl. Cast NiAl has been also investigated for comparison with the MA materials. It exhibited a poor ductility (2.3%) and only 001 dislocations were observed. 001 slip provides only three independent slip systems and the number of independent slip systems is insufficient. The differences between cast and MA NiAl are discussed.
Download or read book The Deformation of NiAl Bicrystals written by Daniel Brian Miracle and published by . This book was released on 1990 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Metals Abstracts Index written by and published by . This book was released on 1996 with total page 1622 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Pandex Current Index to Scientific and Technical Literature written by and published by . This book was released on 1971 with total page 1068 pages. Available in PDF, EPUB and Kindle. Book excerpt:
