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Title: Slip systems and dislocation emission from crack tips in single crystal TiC at low temperatures

Abstract

Low temperature (20--90 0C) plastic deformation in TiC{sub 0.91} single crystals has been studied using microindentations on (111), (001) and (110) surfaces, the dislocation structures around microindents being characterized by transmission electron microscopy (TEM). Deformation occurs primarily by {l_brace}111{r_brace}<1{bar 1}0> and {l_brace}110{r_brace}<1{bar 1}0> slip, with the favored slip system determined by crystal orientation. Indentations below 300 C produced distinct dislocation half loops-hexagonal loops arising from {l_brace}111{r_brace} slip and elongated loops from {l_brace}110{r_brace} slip. At 500 C, much more extensive plastic deformation occurred, accomplished mainly by the motion of edge dislocations from these same systems. The dislocation configurations suggest a relatively high mobility of edge segments and a large Peierls stress for screw dislocations. Thermal activation apparently increases the mobility of screw segments, and results in dislocation structures containing mixed dislocations with no preferred orientation; this signals the onset of the brittle-ductile transition between 700 and 900 C. Cleavage cracks around indents on {l_brace}111{r_brace} and {l_brace}110{r_brace} surfaces introduced below 500 C, but not those on {l_brace}001{r_brace}, arrested with dislocation emission at the crack tips. The emitted dislocations were coplanar dislocation half loops, arising from {l_brace}001{r_brace}<110> slip, and resulted from mode II or mode III loading of the cleavage crack. The localmore » mode II and mode III stress intensity factors must have been sufficiently high to activate {l_brace}001{r_brace} slip, even though this slip system has not, to date, been reported in macroscopic tests.« less

Authors:
; ;  [1]
  1. Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Materials Science and Engineering
Publication Date:
OSTI Identifier:
271771
Resource Type:
Journal Article
Journal Name:
Acta Materialia
Additional Journal Information:
Journal Volume: 44; Journal Issue: 6; Other Information: PBD: Jun 1996
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; TITANIUM CARBIDES; DEFORMATION; FRACTURE PROPERTIES; DISLOCATIONS; SLIP; TEMPERATURE DEPENDENCE; STRESSES; TRANSMISSION ELECTRON MICROSCOPY; ORIENTATION; SCREW DISLOCATIONS; EDGE DISLOCATIONS; BRITTLE-DUCTILE TRANSITIONS; CRACKS; STRESS INTENSITY FACTORS

Citation Formats

Chien, F R, Ning, X J, and Heuer, A H. Slip systems and dislocation emission from crack tips in single crystal TiC at low temperatures. United States: N. p., 1996. Web. doi:10.1016/1359-6454(95)00360-6.
Chien, F R, Ning, X J, & Heuer, A H. Slip systems and dislocation emission from crack tips in single crystal TiC at low temperatures. United States. https://doi.org/10.1016/1359-6454(95)00360-6
Chien, F R, Ning, X J, and Heuer, A H. 1996. "Slip systems and dislocation emission from crack tips in single crystal TiC at low temperatures". United States. https://doi.org/10.1016/1359-6454(95)00360-6.
@article{osti_271771,
title = {Slip systems and dislocation emission from crack tips in single crystal TiC at low temperatures},
author = {Chien, F R and Ning, X J and Heuer, A H},
abstractNote = {Low temperature (20--90 0C) plastic deformation in TiC{sub 0.91} single crystals has been studied using microindentations on (111), (001) and (110) surfaces, the dislocation structures around microindents being characterized by transmission electron microscopy (TEM). Deformation occurs primarily by {l_brace}111{r_brace}<1{bar 1}0> and {l_brace}110{r_brace}<1{bar 1}0> slip, with the favored slip system determined by crystal orientation. Indentations below 300 C produced distinct dislocation half loops-hexagonal loops arising from {l_brace}111{r_brace} slip and elongated loops from {l_brace}110{r_brace} slip. At 500 C, much more extensive plastic deformation occurred, accomplished mainly by the motion of edge dislocations from these same systems. The dislocation configurations suggest a relatively high mobility of edge segments and a large Peierls stress for screw dislocations. Thermal activation apparently increases the mobility of screw segments, and results in dislocation structures containing mixed dislocations with no preferred orientation; this signals the onset of the brittle-ductile transition between 700 and 900 C. Cleavage cracks around indents on {l_brace}111{r_brace} and {l_brace}110{r_brace} surfaces introduced below 500 C, but not those on {l_brace}001{r_brace}, arrested with dislocation emission at the crack tips. The emitted dislocations were coplanar dislocation half loops, arising from {l_brace}001{r_brace}<110> slip, and resulted from mode II or mode III loading of the cleavage crack. The local mode II and mode III stress intensity factors must have been sufficiently high to activate {l_brace}001{r_brace} slip, even though this slip system has not, to date, been reported in macroscopic tests.},
doi = {10.1016/1359-6454(95)00360-6},
url = {https://www.osti.gov/biblio/271771}, journal = {Acta Materialia},
number = 6,
volume = 44,
place = {United States},
year = {1996},
month = {6}
}