Slip transmission of high angle grain boundaries in body-centered cubic metals: Micropillar compression of pure Ta single and bi-crystals

Weaver, Jordan S.; Li, Nan; Mara, Nathan A.; Jones, David R.; Cho, Hansohl; Bronkhorst, Curt A.; Fensin, Saryu; Gray, George T.

doi:10.1016/j.actamat.2018.06.046

Cited by 38 publications

(28 citation statements)

References 46 publications

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“…From the example shown in these figures, it appears that the slip plane corresponding to the slip trace marked by the red solid line is ð1010Þ. A number of previous studies applied the Euler angle or the angle between the c axis of the hexagonal crystal and the loading direction to evaluate the Schmid factor (Weaver et al, 2018;Nan et al, 2012). Here, however, we use a simple convenient method to evaluate the Schmid factor based on the software for orientation imaging microscopy (OIM), in which the Schmid factor is calculated by resolving the stress tensor to a set of principal stresses along with their directions.…”

Section: Slip Trace Analysismentioning

confidence: 99%

How hard metal becomes soft: crystallographic analysis on the mechanical behavior of ultra-coarse cemented carbide

Hu¹,

Liu²,

Hou³

et al. 2019

Acta Crystallogr B Struct Sci Cryst Eng Mater

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Investigation into the temperature dependence of the mechanical behavior of ultra‐coarse grained cemented carbide materials is highly demanded due to its service conditions of concurrent applied stress and high temperature. In the present study, based on the designed experiments and microstructural characterization combined with crystallographic analysis, the evolution of slip systems, motion and interaction of dislocations with temperature are quantified for the WC hard phase. Mechanisms are proposed for the formation of the sessile dislocations in the main slip systems at the room temperature and the glissile dislocations in the new slip systems activated at high temperatures. Furthermore, the correlation of the plastic strain and fracture toughness with the temperature‐dependent slip activation, dislocation reaction and transformation is explained quantitatively. Enlightened by the present findings, potential approach to enhance the high‐temperature strength of ultra‐coarse cemented carbides based on WC strengthening was suggested.

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Section: Slip Trace Analysismentioning

confidence: 99%

How hard metal becomes soft: crystallographic analysis on the mechanical behavior of ultra-coarse cemented carbide

Hu¹,

Liu²,

Hou³

et al. 2019

Acta Crystallogr B Struct Sci Cryst Eng Mater

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“…In Figure 4 , we could see images of micro-pillars with different taper angles after compression in a load-controlled regime. The plastic flow in case of micro-pillars with smaller taper angles (≤7°) was localized in the form of small-scale shear bands that were similar to those observed in the sample MoBC AM ; however, in this case, the coating was composed of nanosized grains, and, thus, the shearing could be explained by grain boundary sliding mechanism that is typical for polycrystalline metallic micro-pillars [ 21 , 22 ]. On the other hand, for higher taper angles in the range between 7° and 12°, the excessive stress concentrations close to the top of micro-pillars resulted in a higher probability of large-scale localized specimen failure.…”

Section: Resultsmentioning

confidence: 96%

“…Figure 3 b shows an image of the corresponding micro-pillar after deformation with the flat punch indenter. We could see that the deformation led to the formation of several shear bands close to the top of the pillar resembling slip traces caused by grain boundary sliding in metals [ 21 , 22 ], albeit, in this case, the coatings posed amorphous microstructure. The sliding mechanism could be explained by the movement of the so-called Somigliana dislocations observed in metallic glasses [ 23 , 24 ].…”

Section: Resultsmentioning

confidence: 99%

The Effect of a Taper Angle on Micro-Compression Testing of Mo-B-C Coatings

et al. 2020

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This research was devoted to studying the influence of the taper angle on the micro-compression of micro-pillars fabricated from near-amorphous and nanocrystalline Mo-B-C coatings. A series of micro-pillars with a taper angle between 4–14° was fabricated by focused ion beam technique. The deformation mechanism was found to be dependent on the taper and, also, on the crystallinity of the coating. In order to obtain correct values of yield strength and Young’s modulus, three empirical models of stress correction were experimentally tested, and the results were compared with nanoindentation measurements. It was shown that the average stress correction model provided comparable results with nanoindentation for the yield strength for taper angles up to ~10°. On the other hand, the average radius or area model gave the most precise results for Young’s modulus if the taper angle was <10°.

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“…The relatively large deviation of measured stress corresponds well to the previous results for bcc metals measured by micropillar compression tests. [22][23][24][25][26][27][28] It is noteworthy that a trend can be observed that σ i becomes higher at higher  ε i ( Fig. 6(a)), which is indicative of strain-rate sensitive stress required for the slip initiation in micronscale single-crystals with a dimeter of 2-3 μm.…”

Section: Compression Tests For Single-crystal Micropillarsmentioning

confidence: 90%

“…However, there are a few reports on micropillar compression tests applied for ferrous materials, [18][19][20][21] regardless of various reports on single-crystal micropillars of pure bcc metals (Cr, Nb, W and Ta). [22][23][24][25][26][27][28] In micro-mechanical testing, size-dependent strength of microscale specimens (smaller is stronger) is generally known in bcc pure metals. 22,27) However, the strength of ferrous materials measured by micro-mechanical testing has been scarcely reported.…”

Section: Strain Rate Sensitivity Of Flow Stress Measured By Micropillmentioning

confidence: 99%

Strain Rate Sensitivity of Flow Stress Measured by Micropillar Compression Test for Single Crystals of 18Cr Ferritic Stainless Steel

Tianqi

Takata

et al. 2020

ISIJ Int.

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We have fabricated cylindrical single-crystal micropillars with different diameter (d) ranges of 2-3 μm and 5-6 μm on a specific grain in the 18Cr ferritic stainless steel with a ferrite single-phase microstructure. The initial strain rate at the onset of plastic deformation was controlled by variable loading rate in the used nanoindenter. The strain rate sensitivity of the stress required for the slip initiation were examined using the fabricated micropillars. The present compression tests addressed the shear stress on an activated single slip system of micron-scale single-crystals. Smaller-sized micropillars (d = 2-3 μm) often exhibit intermittent strain bursts. The stress for slip initiation (after an elastic loading) changes depending on the initial strain rate, resulting in a high strain rate sensitivity (m) of 0.12. Larger-sized micropillars (d = 5-6 μm) show a continuous yielding. A slight change in their yield stress depending on the initial strain rate provides a relatively low m of 0.04. It is similar to one of the millimeter-sized specimens measured by conventional tensile tests. These results provide new insights to optimize the specimen size for the micropillar compression test applied for the 18Cr ferritic stainless steels.

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Slip transmission of high angle grain boundaries in body-centered cubic metals: Micropillar compression of pure Ta single and bi-crystals

Cited by 38 publications

References 46 publications

How hard metal becomes soft: crystallographic analysis on the mechanical behavior of ultra-coarse cemented carbide

How hard metal becomes soft: crystallographic analysis on the mechanical behavior of ultra-coarse cemented carbide

The Effect of a Taper Angle on Micro-Compression Testing of Mo-B-C Coatings

Strain Rate Sensitivity of Flow Stress Measured by Micropillar Compression Test for Single Crystals of 18Cr Ferritic Stainless Steel

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