Fine tungsten precipitates in the matrix phase and their influence on the mechanical properties of a tungsten heavy alloy

This study focuses on numerical prediction and experimental investigation of deformation behaviour of a tungsten heavy alloy prepared via powder metallurgy and subsequent cold (20 °C) and warm (900 °C) rotary swaging. Special emphasis was placed on the prediction of the effects of the applied induction heating. As shown by the results, the predicted material behaviour was in good correlation with the real experiment. The differences in the plastic flow during cold and warm swaging imparted differences in structural development and the occurrence of residual stress. Both the swaged pieces exhibited the presence of residual stress in the peripheries of W agglomerates. However, the NiCO matrix of the warm-swaged piece also exhibited the presence of residual stress, and it also featured regions with increased W content. Testing of mechanical properties revealed the ultimate tensile strength of the swaged pieces to be approximately twice as high as of the sintered piece (860 MPa compared to 1650 MPa and 1828 MPa after warm and cold swaging, respectively).

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Heat Treatment Behavior of Tungsten Heavy Alloy

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.118.35 ◽

2006 ◽

Vol 118 ◽

pp. 35-40 ◽

Cited By ~ 2

Author(s):

Woon Hyung Baek ◽

Moon Hee Hong ◽

Eun Pyo Kim ◽

Joon Woong Noh ◽

Seong Lee ◽

...

Keyword(s):

Heat Treatment ◽

Dynamic Properties ◽

Weight Percent ◽

Matrix Phase ◽

Heavy Alloy ◽

Tungsten Heavy Alloy ◽

Cyclic Heat Treatment ◽

Cyclic Heat ◽

The Difference ◽

The Impact

This paper focuses on the variations of static and dynamic properties of tungsten heavy alloy with heat treatment. The matrix phase of 93W-4.9Ni-2.1Fe (weight percent) has been penetrated into W/W grain boundaries during a cyclic heat treatment which consists of repeated isothermal holdings at 1150 °C and water quenching between them. By applying the cyclic heat treatment, the impact energy of tungsten heavy alloy is increased about three times from 57 to 170 J. When the tungsten heavy alloy is cyclically heat treated at 1150 °C and then re-sintered at 1485 °C, W/matrix interface is changed from round to undulated shape. The irregularity of the interface is increased with increasing the number of heat treatment cycles. From the measurement of the residual stress of W grains by X-ray diffraction, it is found that the irregularity of the interface is closely related with strain energy stemmed from the difference of thermal expansion coefficient between W particles and matrix phase. From dynamic ballistic test, it is found that the tungsten heavy alloy with undulated W grains forms many narrow fracture bands which are preferential for the self sharpening effect, thus, for the improvement of the penetration performance.

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Mechanical properties of all-cellulose composites from end-of-life textiles

Journal of Polymer Research ◽

10.1007/s10965-020-02214-1 ◽

2020 ◽

Vol 27 (9) ◽

Author(s):

Behnaz Baghaei ◽

Sam Compiet ◽

Mikael Skrifvars

Keyword(s):

Mechanical Properties ◽

End Of Life ◽

Composite Laminates ◽

Matrix Phase ◽

Cellulose Solution ◽

Matrix Component ◽

Tensile Impact ◽

Cotton Fibres ◽

Cellulose Composites ◽

The Matrix

Abstract This paper reports the recycling of end-of-life cellulose containing textiles by fabrication of all-cellulose composites (ACCs). Discharged denim fabrics were used as the reinforcement while dissolved cellulose from two different cellulose resources was used as the matrix phase. Virgin cotton fibres and recovered cotton from polyester/cotton (polycotton) waste fabrics were used to form the matrix phase. The process comprises preparing a 6 wt% cellulose solution by dissolving cellulose solution in a ionic liquid, 1-butyl-3-methyl imidazolium acetate ([BMIM][Ac]), this solution acted as a precursor for the matrix component. The denim fabrics were first embedded in the cellulose/IL solution followed by removal of the IL by washing to form the composite. The effect of reuse of the recovered IL by distillation was also investigated. The mechanical properties of the obtained ACCs were determined regarding tensile, impact and flexural properties. Fabricated ACC composite laminates were further characterised regarding structure by scanning electron microscopy.

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Effects of Cobalt Content on the Microstructure, Mechanical Properties and Cavitation Erosion Resistance of HVOF Sprayed Coatings

Coatings ◽

10.3390/coatings9090534 ◽

2019 ◽

Vol 9 (9) ◽

pp. 534 ◽

Cited By ~ 8

Author(s):

Liu ◽

Bai ◽

Chen ◽

Yuan

Keyword(s):

Mechanical Properties ◽

Fracture Toughness ◽

Surface Roughness ◽

Cavitation Erosion ◽

Cobalt Content ◽

Alloy Coating ◽

Matrix Phase ◽

Hvof Spraying ◽

The Matrix ◽

Cavitation Erosion Resistance

Cobalt-based alloy coatings and WC-Co-based ceramic–metal (cermet) coatings have been widely used because of their desirable mechanical properties and corrosion resistance. In this work, the influence of Co content on the microstructure, mechanical properties and cavitation erosion (CE) resistance were investigated. A cobalt-based alloy coating, a WC-12Co coating, and a WC-17Co cermet coating were deposited by high-velocity oxygen fuel (HVOF) spraying on 1Cr18Ni9Ti substrates. Results indicate that the cobalt-based alloy coating had the largest surface roughness because surface-bonded particles of lower plastic deformation were flattened. The existence of WC particles had led to an increase in hardness and improved the fracture toughness due to inhibit crack propagation. The pore appeared at the interface between WC particles, and the matrix phase had introduced an increase in porosity. With the increase in Co content, the cohesion between matrix friction and WC particles increased and then decreased the porosity (from 0.99% to 0.84%) and surface roughness (Ra from 4.49 to 2.47 μm). It can be concluded that the hardness had decreased (from 1181 to 1120 HV0.3) with a decrease in WC hard phase content. On the contrary, the fracture toughness increased (from 4.57 to 4.64 MPa∙m1/2) due to higher energy absorption in the matrix phase. The WC-12Co and WC-17Co coatings with higher hardness and fracture toughness exhibited better CE resistance than the cobalt-based alloy coating, increasing more than 20% and 16%, respectively. Especially, the WC-12Co coating possessed the best CE resistance and is expected to be applicable in the hydraulic machineries.

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Evaluation of mechanical properties of fiber reinforced composites filled with hollow spheres: A micromechanics approach

Journal of Composite Materials ◽

10.1177/0021998320949649 ◽

2020 ◽

pp. 002199832094964

Author(s):

Mojde Biarjemandi ◽

Ehsan Etemadi ◽

Mojtaba Lezgy-Nazargah

Keyword(s):

Mechanical Properties ◽

Elastic Constants ◽

Volume Fraction ◽

Hollow Spheres ◽

Matrix Phase ◽

Fiber Reinforced Composites ◽

Fiber Direction ◽

Reinforced Composites ◽

Fiber Reinforced ◽

The Matrix

Recent researches show that the embedment of hollow spheres in the matrix phase of composite materials improves the strength of these structures against crack propagations. Rare studies are reported for calculating equivalent elastic constants of fiber reinforced composites containing hollow spheres. In this paper, the effects of hollow spheres on mechanical characteristics of fiber reinforced composite are studied for the first time. To achieve this aim, a micromechanics based finite element method is employed. Representative volume elements (RVEs) including hollow spheres with different radius, thickness and volume fraction of hollow spheres, are modeled by using 3D finite elements. The equivalent elastic constants are calculated through homogenization technique. The results are compared with available experimental works. Good agreements find between two sets of results. Also, the volume fraction, number and thickness of hollow spheres as effective parameters on mechanical properties of composite were investigated. The results show the equivalent elastic properties increase with increasing the volume fraction and number of hollow spheres and decrease with increasing the number of hollow spheres. Furthermore, the equivalent Young’s modulus in transverse directions to the fiber direction and shear modulus of the composite increase with increasing the thickness of hollow spheres. As a final result, the presence of hollow spheres in the matrix phase generally increases the equivalent elastic constants without significant changes in the weight of structures.

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Mechanical and Fatigue Properties of Tungsten Heavy Alloy Prepared by RF-Plasma

Thermal Spray 2021: Proceedings from the International Thermal Spray Conference ◽

10.31399/asm.cp.itsc2021p0115 ◽

2021 ◽

Author(s):

Ondřej KovářÍk ◽

Jaroslav Čech ◽

Jan Cizek ◽

Jakub Klečka ◽

Michal Hajíček

Keyword(s):

Mechanical Properties ◽

Crack Growth ◽

Heavy Alloy ◽

Fatigue Properties ◽

Protective Atmosphere ◽

Rf Plasma ◽

Tungsten Heavy Alloy ◽

Threshold Region ◽

Early Results ◽

Near Threshold

Abstract Tungsten heavy alloy (WHA) of W-Ni composition was deposited from a blend of standard thermal spray powders using radio frequency inductively coupled plasma torch (RF-ICP) in a protective atmosphere. The deposit (RF WHA) contained a fully developed WHA structure; i.e.; spherical W particles embedded in a Ni-rich matrix. The bending tensile strength Rm; bending yield strength Rp;0.2; and elastic modulus of the deposit were compared with two W-Ni-Co references fabricated by powder metallurgy (PM WHA) via sintered and quenched (PMSQ); and forged and annealed (PM-FA). While the RF deposit properties are comparable with the PM-SQ reference; the PMFA exhibited higher mechanical properties. The deposit showed very limited ductility A < 3%. The fatigue crack growth rate in the deposit measured in bending (R < -1) was comparable to the PM-SQ reference material in the near-threshold region whereas the forged PM-FA had significantly better fatigue performance. In the near-threshold fatigue regime; the crack growth took place in the Ni-rich matrix. In the Paris regime; the similar fracture mode was observed; with the exception of PM-SQ; where the tungsten particles fracture contributed significantly. The static failure was exclusively trans-particle in RF WHA; while both PM WHAs failed by a mix of ductile matrix failure and trans-particle cleavage fracture. The fracture toughness of the deposit was significantly lower than the references. These early results indicate that RF-plasma spray is a suitable and efficient manufacturing method for production of WHA materials; however with limited mechanical properties in some aspects.

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The Influence of Cyclic Sintering on the Structure and Mechanical Properties of Tungsten Heavy Alloy

Archives of Foundry Engineering ◽

10.1515/afe-2016-0097 ◽

2016 ◽

Vol 16 (4) ◽

pp. 131-136 ◽

Cited By ~ 1

Author(s):

P. Skoczylas ◽

M. Kaczorowski

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Main Part ◽

Hydrogen Atmosphere ◽

Liquid Phase Sintering ◽

Heavy Alloy ◽

Tungsten Heavy Alloy ◽

Structure Investigations ◽

Scanning Electron ◽

Mechanical Studies

Abstract The results of structure and mechanical properties investigations of tungsten heavy alloy (THA) after cyclic sintering are presented. The material for study was prepared using liquid phase sintering of mixed and compacted powders in hydrogen atmosphere. The specimens in shape of rods were subjected to different number of sintering cycles according to the heating schemes given in the main part of the paper From the specimens the samples for mechanical testing and structure investigations were prepared. It follows from the results of the mechanical studies, that increasing of sintering cycles lead to decrease of tensile strength and elongation of THA with either small or no influence on yield strength. In opposite to that, the microstructure observations showed that the size of tungsten grain increases with number of sintering cycles. Moreover, scanning electron microscope (SEM) observations revealed distinctly more trans-granular cleavage mode of fracture in specimens subjected to large number of sintering cycles compared with that after one or two cycles only.

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