Variation of Hardness of Metals with Grain Size

Hall, E. O.

doi:10.1038/173948b0

Cited by 233 publications

(61 citation statements)

References 2 publications

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“…[10][11][12][13][14][15] Aside from quantitative improvements in fatigue performance, NC metals also hold the possibility of new insight into the mechanisms responsible for traditional fatigue failure. In the recent past, studies on the monotonic strength of NC metals have not only revealed quantitative details regarding the Hall-Petch strengthening effect, [16][17][18] but also led to the discovery of mechanistic transitions in dislocation behavior. For example, while individual dislocation slip is still active in NC metals with a grain size in the range of 20 to 50 nm, [4,19,20] there is insufficient space for the collective dislocation interaction mechanisms found in CG metals such as pileups and subgrain formation.…”

Section: Introductionmentioning

confidence: 99%

Anomalous Fatigue Behavior and Fatigue-Induced Grain Growth in Nanocrystalline Nickel Alloys

Boyce

Padilla

2011

Metall Mater Trans A

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Fatigue failure due to repetitive loading of metallic devices is a pervasive engineering concern. The present work reveals extraordinary fatigue resistance in nanocrystalline (NC) alloys, which appears to be associated with the small (<100 nm) grain size inhibiting traditional cyclic damage processes. In this study, we examine the fatigue performance of three electrodeposited NC Nibased metals: Ni, Ni-0.5Mn, and Ni-22Fe (PERMALLOY). When subjected to fatigue stresses at and above the tensile yield strength where conventional coarse-grained (CG) counterparts undergo low-cycle fatigue failure (<10 4 cycles to failure), these alloys exhibit exceptional fatigue lives (in some cases, >10 7 cycles to failure). Postmortem examinations show that failed samples contain an aggregate of coarsened grains at the crack initiation site. The experimental data and accompanying microscopy suggest that the NC matrix undergoes abnormal grain growth during cyclic loading, allowing dislocation activity to persist over length scales necessary to initiate a fatigue crack by traditional fatigue mechanisms. Thus, the present observations demonstrate anomalous fatigue behavior in two regards: (1) quantitatively anomalous when considering the extremely high stress levels needed to drive fatigue failure and (2) mechanistically anomalous in light of the grain growth process that appears to be a necessary precursor to crack initiation.

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Section: Introductionmentioning

confidence: 99%

Anomalous Fatigue Behavior and Fatigue-Induced Grain Growth in Nanocrystalline Nickel Alloys

Boyce

Padilla

2011

Metall Mater Trans A

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“…Eshelby et al [1], showed analytically that the dislocation pile up ahead an insurmountable obstacle such as grain boundary would result in a stress gradient that varies as 'one over square root' of the distance from the obstacle. Subsequent experimental observations by Hall [2], [3], and Petch [4], independently reestablished such a behavior in metals as the well-known Hall-Petch effect, wherein the mechanical strength of the material increases with decreasing grain size.…”

Section: Introductionmentioning

confidence: 99%

Experimental Determination and Theoretical Analysis of Local Residual Stress at Grain Scale

Basu¹,

Ocelík²,

Hosson³

2017

WIT Transactions on Engineering Sciences

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Grain/phase boundaries contribute significantly to build up of residual stresses, owing to varied plastic/thermal response of different grain orientations or phases during thermomechanical treatment. Hence, accurate quantification of such local scale stress gradients in commercial components is important in understanding their mechanical performance. The current work introduces a correlative method utilizing Electron Back Scattered Diffraction and Focused Ion Beam -Digital Image slit milling methodology to accurately determine spatially resolved stress profiles in the vicinity of grain boundaries using commercially pure titanium as a model material. Measured local stress gradients were in good agreement with local misorientation values. The role of dislocation-grain boundary interactions on buildup of local stress gradients is elucidated. Stress profiles near grain boundaries initially display non Hall-Petch characteristics, followed by a typical Hall-Petch type variation of "one over square root of distance". The observed trends allude to local stress relaxation mechanisms very close to the grain boundaries. The findings indicate that grain scale stress gradients can be significant in terms of playing a crucial role in macroscopic fatigue behavior.

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“…The very high microhardness of the Xe C polycrystal as compared to that of the C 60 single crystal may be caused by two factors: (i) the hardening effects of both the intergrain boundaries and secondly (ii) the minor second phase particles within the crystalline grains. By the Hall-Petch relation [15], the yield stress and microhardness of a polycrystal are higher than those of a single crystal by an amount inversely proportional to the square root of polycrystal grain size. The second-phase fine particles form local barriers which impede dislocation slip, reducing appreciably the plastic compliance and increasing the microhardness of the material (that mechanism of hardening is well known in the physics of ageing alloy plasticity [16]).…”

Section: Ls Fomenko Sv Lubenets Vd Natsik D Cassidy Ge Gmentioning

confidence: 99%

Low-temperature microhardness of Xe-intercalated fullerite C60

Fomenko

Lubenets

Нацик

et al. 2005

Low Temperature Physics

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The Vickers microhardness of Xe-intercalated polycrystalline fullerite C 60 (Xe C x 60 , x 0.35) is measured in a moderately low temperature range of 77 to 300 K. A high increase in the microhardness of the material (by a factor of 2 to 3) as compared to that of pure C 60 single crystals is observed. It is shown that the step-like anomaly in the temperature dependences of the microhardness of pure C 60 single crystals recorded under the orientational fcc-sc phase transition (T c 260 K) is also qualitatively retained for Xe C x 60 , but its onset is shifted by 40 K towards lower temperatures and the step becomes less distinct and more smeared. This behavior of H T V ( ) correlates with x-ray diffraction data, the analysis of which revealed a considerable influence of xenon interstitial atoms on the peculiar features of fullerite thermal expansion due to orientational phase transitions (see the paper by A.I. Prokhvatilov et al. in this issue).

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Variation of Hardness of Metals with Grain Size

Cited by 233 publications

References 2 publications

Anomalous Fatigue Behavior and Fatigue-Induced Grain Growth in Nanocrystalline Nickel Alloys

Anomalous Fatigue Behavior and Fatigue-Induced Grain Growth in Nanocrystalline Nickel Alloys

Experimental Determination and Theoretical Analysis of Local Residual Stress at Grain Scale

Low-temperature microhardness of Xe-intercalated fullerite C60

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