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Besterci M., Velgosová O., Ivan J., Kvačkaj T. |
THE MECHANICAL PROPERTIES AND FRACTURE MECHANISM OF Al-Al4C3 SYSTEM INVESTIGATED BY “IN-SITU TENSILE TEST IN SEM” METHOD |
Abstract
Dispersion strengthened materials belong to the group of composite materials, which are made mainly by the techniques of powder metallurgy. Their structure is formed with a polycrystalline matrix, in which dispersion particles are incorporated, mainly of the oxide, carbide and nitride types. The strengthening effect of dispersoids is both direct, based on the braking of the matrix dislocation movement, and indirect, resulting from a. forming, dispersoids increase the density of dislocations and refine the grain and subgrain structure. The effectiveness of the strengthening effect of dispersoids depends on their type, size, morphology, volume fraction and distribution. Their resistance against dissolution and coalescence is an important factor in their strengthening effect, mainly at high temperatures.
The method of “in-situ tensile testing in SEM” is suitable for investigations of fracture mechanisms because it enables to observe and document deformation processes directly, by which the initiation and development of plastic deformation and fracture can be reliably described.
With increasing tensile load, local cracks are formed by rupture of large particles and decohesion of smaller particles. Further increase of load leads to the crack growth by coalescence of cavities in the direction from the surface to the specimen centre. The cracks can be oriented parallel or perpendicular to the loading direction in depending on the particle volume fraction. The final rupture takes place in variably dense rows, depending on the volume fractions of carbide (Al4C3) and oxide (Al2O3) particles.
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Keywords: composite material|“in-situ tensile testing in SEM”|fracture mechanisms| |
No 1 (2008), p. 7-16 |
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Brehuv J., Magula R. |
KNOWN AND UNKNOWN MINING-PROCESSING ACTIVITIES OF ARISTOCRATIC FAMILY „DE SOÓSO“ |
Keywords: |
No 1 (2008), p. 172-176 |
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