Micromechanisms of deformation and failure at successive stages of compressive loading of hard alloys WC-Co

Chernyavskii, K. S.; Travushkin, G. G.; Sapronova, Z. N.; Александрович, Акимов Александр

doi:10.1007/bf00777122

Cited by 6 publications

(3 citation statements)

References 2 publications

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“…The design of new high-efficiency grades of hard alloys, the improvement in the mechanical characteristics of sintered high-load hard alloy pieces that operate under cyclic dynamic loads (for example, drilling and upsetting tools, die presses, high pressure apparatus) have made it necessary to establish the deformation and fracture behavior of alloys during use [1][2][3][4][5][6][7][8][9][10]. However, generally the object of these investigations have not been alloys widely used in industry but rather model alloys, in which large carbide grains and wide cobalt interlayers make it possible to identify traces of deformation and fracture in the individual phase components.…”

Section: Introductionmentioning

confidence: 99%

Metallographic Aspects of Deformation and Fracture of Hard Alloys under Compression

Aleksandrova

Бондаренко

Loshak

2005

Powder Metall Met Ceram

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669.018.25We have studied the mechanism of plastic deformation and fracture of tungsten-cobalt hard alloys over a broad range of compositions and grain sizes of the carbide phase in different stages of loading by uniaxial compression. We have shown that the behavior of each phase component is due to the cobalt content in the alloy and the tungsten carbide grain size. When the alloys are loaded to the yield stress, microcracks appear in them which are stopped at this stage by the deformed layers of the alloy. Residual strain of the hard alloys under uniaxial compression is the result of at least three deformation processes occurring in the alloys when they are loaded: slip along interphase and intergrain boundaries with the appearance of microcracks at this sites, slip in WC grains, and deformation of the cobalt phase. We conclude that slip in the cobalt phase is one of the basic mechanisms for its deformation when the alloys are loaded by compression.

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Section: Introductionmentioning

confidence: 99%

Metallographic Aspects of Deformation and Fracture of Hard Alloys under Compression

Aleksandrova

Бондаренко

Loshak

2005

Powder Metall Met Ceram

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“…On loading a short specimen of low-plasticity material, a combined nonhomogeneous stress-strain state arises in it, which is due to the influence of end effects. As a result, the total strain may differ noticeably from local strain in the middle section [3]. Note also that the method for measuring local strain, which is employed in [3], is probably insufficiently precise.…”

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confidence: 98%

“…Therefore, such experimental characteristics as yield strength, ultimate plastic strain, unit plastic work of deformation [16] are conventional and do not correspond to the generally accepted meaning. This becomes obvious if the specimen destruction evolution is taken into consideration [3]. For example, in [16] gives Conclusions.…”

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confidence: 99%

On the calculation of deformation curves for two-phase cermets

Golovchan

2006

Strength Mater

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Analytical algorithms for the construction of tensile and compression stress-strain diagrams of two-phase cermets are proposed, which are based on the concept of mean stresses in the phase volume and physical equations of the theory of small elastoplastic strains. The deformation properties and strength of cermet are supposed to depend on such parameters of its microstructure as mean size and coefficient of variation of solid phase grain-size distribution, contiguity coefficient of solid phase grains, and mean thickness of the metal phase inter-layers. A numerical analysis of the characteristic parameters of deformation curves for WC-Co hard metals has been carried out over a wide range of cobalt concentration and carbide grain size. A good agreement between the theoretical values of ultimate tensile and compression strength and known experimental values has been established. The constructed model deformation curves for hard metals may be regarded as alternatives to the corresponding experimental curves of stress against relative change in specimen length.Keywords: cermet, WC-Co hard metal, tensile and compression stress-strain diagrams, strength and plasticity.Introduction. Cermets (metal ceramics) are a large class of heterogeneous materials that are used in structures and tools [1]. Thanks to the combination of a refractory and brittle nonmetallic phase and a plastic metallic phase, the composites possess physicomechanical and performance characteristics which differ substantially from those of their constituents. Experimental deformation curves are generally constructed as plots of axial force P vs. change in specimen length Δl (displacement of movable specimen grip) [2]. The replacement of elongation Δl by total strain in the bar ε = Δl l 0 and of axial force P by stress σ = P F does not practically transform such curves into stress-strain curves, which are traditional in the mechanics of materials, even in the case of cylindrical specimen. On loading a short specimen of low-plasticity material, a combined nonhomogeneous stress-strain state arises in it, which is due to the influence of end effects. As a result, the total strain may differ noticeably from local strain in the middle section [3]. Note also that the method for measuring local strain, which is employed in [3], is probably insufficiently precise.The initial portion of deformation curves for WC-Co hard metals was calculated in [4] by the finite element method and in [5-7] on the basis of mean stresses in the phase volume. The present paper proposes an analytical algorithm for the construction of deformation curves for two-phase cermets, which is based on the basic relations of the micromechanics of macroscopically isotropic composite materials with allowance for their microstructure features. In this case, the process of loading the specimen up to its failure is investigated. Since the tensile and compressive strain resistance of cermets is different, tensile and compression stress-strain diagrams are considered separately. In both cases, numerica...

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Spiral point drill temperature and stress in high-throughput drilling of titanium

Shih

2007

International Journal of Machine Tools and Manufacture

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Micromechanisms of deformation and failure at successive stages of compressive loading of hard alloys WC-Co

Cited by 6 publications

References 2 publications

Metallographic Aspects of Deformation and Fracture of Hard Alloys under Compression

Metallographic Aspects of Deformation and Fracture of Hard Alloys under Compression

On the calculation of deformation curves for two-phase cermets

Spiral point drill temperature and stress in high-throughput drilling of titanium

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