Dislocation–grain boundary interactions in martensitic steel observed through in situ nanoindentation in a transmission electron microscope

Dislocation–interface interactions in Fe–0.4 wt% C tempered martensitic steel were studied through in situ nanoindentation in a transmission electron microscope (TEM). Two types of boundaries were imaged in the dislocated martensitic structure: a low-angle (probable) lath boundary and a coherent, high-angle (probable) block boundary. In the case of a low-angle grain boundary, the dislocations induced by the indenter piled up against the boundary. As the indenter penetrated further, a critical stress appeared to have been reached, and a high density of dislocations was suddenly emitted on the far side of the grain boundary into the adjacent grain. In the case of the high-angle grain boundary, the numerous dislocations that were produced by the indentation were simply absorbed into the boundary, with no indication of pileup or the transmission of strain. This surprising observation is interpreted on the basis of the crystallography of the block boundary.

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Indentation-Induced Deformation Behavior in Martensitic Steel Observed through In Situ Nanoindentation in a Transmission Electron Microscopy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.503-504.239 ◽

2006 ◽

Vol 503-504 ◽

pp. 239-244 ◽

Cited By ~ 3

Author(s):

Takahito Ohmura ◽

A. Minor ◽

Kaneaki Tsuzaki ◽

J.W. Morris

Keyword(s):

Grain Boundary ◽

Deformation Behavior ◽

Critical Stress ◽

Martensitic Steel ◽

High Angle ◽

Block Boundary ◽

Density Of Dislocations ◽

Transmission Electron ◽

Pile Up

Deformation behavior in the vicinity of grain boundary in Fe-0.4wt%C tempered martensitic steel were studied through in-situ nanoindentation in a TEM. Two types of boundaries were imaged in the dislocated martensitic structure: a low-angle lath boundary and a high-angle block boundary. In the case of a low-angle grain boundary, the dislocations induced by the indenter piled up against the boundary. As the indenter penetrated further, a critical stress appears to have been reached and a high density of dislocations was suddenly emitted on the far side of the grain boundary into the adjacent grain. In the case of the high-angle grain boundary, the numerous dislocations that were produced by the indentation were simply absorbed into the boundary, with no indication of pile-up or the transmission of strain.

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Grain Boundary Responses to Local and Applied Stress: An In Situ TEM Deformation Study

MRS Proceedings ◽

10.1557/proc-976-0976-ee02-01 ◽

2006 ◽

Vol 976 ◽

Author(s):

Bryan Miller ◽

Jamey Fenske ◽

Dong Su ◽

Chung-Ming Li ◽

Lisa Dougherty ◽

...

Keyword(s):

Electron Microscope ◽

Grain Boundary ◽

Grain Boundaries ◽

Grain Growth ◽

Transmission Electron Microscope ◽

In Situ Tem ◽

Deformation Twins ◽

Transmission Electron ◽

Dislocation Interactions

AbstractDeformation experiments at temperatures between 300 and 750 K have been performed in situ in the transmission electron microscope to investigate dislocation interactions and reactions with grain boundaries and other obstacles. Dislocations, both partial and perfect, as well as deformation twins have been observed being emitted from grain boundaries and, in some cases, even the same grain boundary. The ejection of dislocations from the grain boundary can result in its partial or total annihilation. In the latter case, the disintegration of the grain boundary was accompanied by grain growth and a change in misorientation.

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Study of Deformation Behavior of Ultrafine-grained Materials Through in Situ Nanoindentation in a Transmission Electron Microscope

Journal of Materials Research ◽

10.1557/jmr.2005.0216 ◽

2005 ◽

Vol 20 (7) ◽

pp. 1735-1740 ◽

Cited By ~ 16

Author(s):

M. Jin ◽

A.M. Minor ◽

D. Ge ◽

J.W. Morris

Keyword(s):

Electron Microscope ◽

Grain Boundary ◽

Transmission Electron Microscope ◽

Deformation Behavior ◽

Boundary Migration ◽

Boundary Motion ◽

Transmission Electron ◽

Ultrafine Grained ◽

Grain Boundary Motion

The mechanical properties of ultrafine-grained and nanograined materials have received a great deal of recent attention because of their unusual and promising values. However, some of the most important mechanisms of deformation remain unclear. In this work, the deformation behavior of ultrafine-grained Al films and ultrafine-grained Fe is studied through in situ nanoindentation in a transmission electron microscope. Deformation-induced coarsening by grain boundary migration was observed in the ultrafine-grained Al films during deformation at room temperature, whereas no grain boundary motion was found in ultrafine-grained Fe. The lack of grain boundary motion in Fe was attributed to the pinning effect of nano-sized particles at the Fe grain boundaries.

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Dislocation structures in deformed Ni3Al

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010015349x ◽

1989 ◽

Vol 47 ◽

pp. 304-305

Author(s):

Raja Subramanian ◽

I.M. Robertson ◽

H.K. Birnbaum

Keyword(s):

Boundary Layer ◽

Electron Microscope ◽

Grain Boundary ◽

Transmission Electron Microscope ◽

Cohesive Energy ◽

Intermetallic Alloys ◽

Transmission Electron ◽

Deviation From Stoichiometry

The improvement of the ductility of Ni3Al by the addition of boron has revived interest in intermetallic alloys. Addition of up to about 500 wt. ppm of boron increases the ductility of Ni3Al by as much as 50%. This improvement is dependent on the deviation from stoichiometry with optimum effect being obtained for the Ni-rich composition. The ductility enhancement has been attributed to the boron increasing the cohesive energy of the grain boundary and to a disordered boundary layer easing the slip process through the grain boundary.The dislocation structures produced in deformed Ni3Al with and without boron has been examined in the transmission electron microscope . Samples were deformed to a 3 % strain in bulk form while others were deformed in situ in the transmission electron microscope. (Details of the in situ TEM straining technique can be found in ref.)

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Remote On-Line Control of a High-Voltage in situ Transmission Electron Microscope with A Rational User Interface

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100164386 ◽

1996 ◽

Vol 54 ◽

pp. 384-385

Author(s):

M.A. O’Keefe ◽

J. Taylor ◽

D. Owen ◽

B. Crowley ◽

K.H. Westmacott ◽

...

Keyword(s):

Electron Microscopy ◽

Electron Microscope ◽

User Interface ◽

Transmission Electron Microscope ◽

High Voltage ◽

Materials Science ◽

Transmission Electron ◽

On Line ◽

Electron Microscopes

Remote on-line electron microscopy is rapidly becoming more available as improvements continue to be developed in the software and hardware of interfaces and networks. Scanning electron microscopes have been driven remotely across both wide and local area networks. Initial implementations with transmission electron microscopes have targeted unique facilities like an advanced analytical electron microscope, a biological 3-D IVEM and a HVEM capable of in situ materials science applications. As implementations of on-line transmission electron microscopy become more widespread, it is essential that suitable standards be developed and followed. Two such standards have been proposed for a high-level protocol language for on-line access, and we have proposed a rational graphical user interface. The user interface we present here is based on experience gained with a full-function materials science application providing users of the National Center for Electron Microscopy with remote on-line access to a 1.5MeV Kratos EM-1500 in situ high-voltage transmission electron microscope via existing wide area networks. We have developed and implemented, and are continuing to refine, a set of tools, protocols, and interfaces to run the Kratos EM-1500 on-line for collaborative research. Computer tools for capturing and manipulating real-time video signals are integrated into a standardized user interface that may be used for remote access to any transmission electron microscope equipped with a suitable control computer.

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