Initial dislocation distributions in tungsten fibre-copper composites

Chawla, K. K.; Metzger, M.

doi:10.1007/bf00549547

Cited by 157 publications

(32 citation statements)

References 10 publications

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“…These include etch-pit studies to characterize low density dislocation structures near second phases [19,20], conventional or synchrotron X-ray di raction as well as neutron di raction studies, of as-processed (e.g. [21,22]) or strained samples (e.g.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation of stress and strain fields in a ductile matrix surrounding an elastic inclusion

2000

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AbstractÐA method for measuring stress and strain distributions within a ductile material deforming by dislocational slip is developed. The method exploits the transparency and room-temperature ductility of silver chloride, and combines the techniques of photoelasticity and marker tracking. This method is used to investigate the deformation of an elasto-plastic ductile matrix surrounding an isolated sti ®ber, the grain size of the material being slightly smaller than the ®ber length. The data are compared to predictions of ®nite element calculations which take the matrix to be an isotropic elasto-plastic von Mises continuum. It is found that this model does not fully capture all of the features of the experimental data. Data suggest that the cause for observed discrepancies is the strong in¯uence exerted by grain boundaries and grain orientation on the distribution of stress and strain within the matrix. A comparison is also made between the data and predictions of the Eshelby equivalent inclusion calculation, to show that a far higher level of discrepancy results than with the ®nite element calculations; this is caused by the fact that the Eshelby equivalent inclusion calculation is essentially elastic and thus allows signi®cant stress concentrations. 7

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Section: Introductionmentioning

confidence: 99%

Experimental investigation of stress and strain fields in a ductile matrix surrounding an elastic inclusion

2000

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“…The radius) after heat treatment and submicron ranmatrix was prepared from 99.999% pure silver dom precipitation of silver (fog) within the chloride (purchased from Engelhard, OH, volume upon exposure to actinic light. The matrix U.S.A.) doped with 0.05% cuprous chloride of the around the particles exhibited much higher den- (1). A wall of dislocations perpendicular to the image plane forms a subgrain boundary (2).…”

Section: Resultsmentioning

confidence: 99%

“…Plasticity due to thermal incompatibilparent model material for the matrix of particleity has been studied experimentally in metals reinforced MMCs. It is well known that silver reinforced with particles, whiskers and fibers chloride is very ductile (up to 400% tensile using etch pits [1,2], slip lines [3] as well as transelongation) and that it exhibits dislocation mission electron microscopy (TEM) [4][5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Thermal mismatch dislocations produced by large particles in a strain-hardening matrix

Dunand

Mortensen

1991

Materials Science and Engineering: A

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Silver chloride containing particles of irregular form of the order of 1 ktm in diameter is used as a model material for particle-reinforced metal matrix composites (MMCs). Matrix dislocations due to the mismatch of the coefficients of thermal expansion of the two phases are made visible to transmission optical microscopy through bulk decoration performed at room temperature. The plastic zone around the particles takes two forms, similar to what is observed around the glass microspheres: (a) rows of coaxial prismatic dislocation loops punched into the matrix and (b) a plastic zone of irregular form containing partially resolved tangled dislocations. A relationship between the inclusion volume and the volume of the plastic zone around the inclusion--developed for the geometrically tractable problem of a sphere embedded in a strain-hardening matrix deforming by slip--is found to be valid for particles of irregular form as well, which are more representative of the reinforcement used in MMCs than spheres [ire.

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“…8). Since the stress and strain state, as well as strain history of the matrix are identical for these two cases of a thermally mismatching inclusion and a growing hole, the size of the plastic zone can be found by deriving ac or a~, and using equation (1). The radii a¢ and as are most easily derived from conservation of volume, neglecting the elastic compressive strain within the inclusion volume in the growing hole configuration.…”

Section: Theorymentioning

confidence: 99%

“…It is well documented that, if these thermal stresses are high enough, dislocations are produced in metal matrix composites (MMCs) near fibers, whiskers or particles. This phenomenon has been studied experimentally using etch pits [1,2], slip lines [3] as well as transmission electron microscopy (TEM). This latter technique has revealed a variety of dislocation configurations surrounding the reinforcing phase, including long dislocations along fibers [4][5][6], dislocations emitted at whisker ends and corners [7,8] as well as various loops and tangles [9,10].…”

Section: Introductionmentioning

confidence: 99%

On plastic relaxation of thermal stresses in reinforced metals

1991

Composites

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Abstract--Silver chloride containing alumina fibers or glass microspheres is used as a model material to study matrix plasticity induced by thermal mismatch in metal matrix composites. Resulting matrix dislocations are decorated at room temperature in the bulk material and observed by optical microscopy. Plastic deformation of the matrix around the inclusions is found to take the form of (i) rows of prismatic dislocation loops punched into the matrix and/or (ii) a plastic zone containing tangled dislocations surrounding the inclusions. From the number of loops punched by spheres, the temperature interval over which slip of prismatic loops is operative is calculated to be 100 + 30 K wide. The stress in the plastic zone around fibers is determined from the radius of curvature of pinned dislocations, leading to the conclusion that the matrix is locally strain-hardened. A simple model taking this fact into account is proposed to predict the radius of the plastic zone around embedded cylinders and spheres and is compared to the experimental data.Rrsum~-Le chlorure d'argent contenant des fibres d'alumine ou des microsphrres de verre est utilis6 pour 6tudier la plasticit6 induite par incompatibilit6 thermique darts la matrice de matrriaux composites matrice m&allique. Les dislocations qui en rrsultent sont drcorres dans la matrice ~i temprrature ambiante et observres par microscopie optique. La drformation plastique de la matrice autour de ces inclusions se manifeste par (i) des rangres de boucles de dislocations prismatiques et/ou (ii) une zone plastique contenant des dislocations emmrlres autour des inclusions. A partir du nombre de boucles engendrres par les sphrres, une valeur de I00 _.+ 30 K est calculre pour l'intervale de temprrature pendant lequel le glissement de boucles prismatiques est oprrationel. La tension dans la zone plastique autour de la fibre est ddterminre ~. partir du rayon de courbure de dislocations bloqures, ce qui conduit ~ la conclusion que la matrice est localement 6crouie. Un modrle simple tenant compte de ce fait est propos6 pour prrdire le rayon de la zone platique autour de cylindres ou de sphdres et compar6 aux donnres exprrimentales.Zusammenfassung--Silberchlorid mit Aluminiumoxid Fasern oder Glassmikrokugeln wird als Modellmaterial beniitzt, um die thermisch induzierte Matrixplastizit/it in Verbundwerkstoffen mit metallischer Matrix zu studieren. Resultierende Matrixversetzungen werden bei Raumtemperatur im Materialinnern dekoriert und durch optische Mikroskopie beobachtet. Plastische Verformung der Matrix um die Einschlfisse wird in Form von (i) Reihen yon in die Matrix ausgestossenen prismatischen Versetzungsringen und/oder (ii) einer plastischen Zone, die Versetzunganh/iufungen um den Einschluss enth/ilt, beobachtet. Aus der Zahl der von den Kugeln ausgestossenen Ringen wird das Temperaturinterval, w/ihrend dessen Gleitung prismatischer Ringe wirksam ist, als 100 + 30 K ausgerechnet. Die Spannung in der plastischen Zone um die Fasern wird aus dem Kriimmungsradius blockierter Versetz...

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Initial dislocation distributions in tungsten fibre-copper composites

Cited by 157 publications

References 10 publications

Experimental investigation of stress and strain fields in a ductile matrix surrounding an elastic inclusion

Experimental investigation of stress and strain fields in a ductile matrix surrounding an elastic inclusion

Thermal mismatch dislocations produced by large particles in a strain-hardening matrix

On plastic relaxation of thermal stresses in reinforced metals

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