Characteristics of densification and distortion of Ni–Cu liquid-phase sintered tungsten heavy alloy

Wu, Yixian; German, Randall M.; Marx, Brian M.; Bollina, Ravi; Bell, Matthew

doi:10.1016/s0921-5093(02)00424-0

Cited by 38 publications

(24 citation statements)

References 17 publications

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“…4. The density is constant and it has reached theoretical full density prior to distortion, as observed by Wu et al [2,3] 5. The model is axisymmetric (field quantities are independent of and u ϭ 0).…”

Section: A Equationsmentioning

confidence: 54%

“…The mesh was also created to take into account the anticipated total deformation usually observed in experiments. [2,3] Since these spines needed to be normal to the free surface, the meshing of a square section caused a difficulty because the square element normally used will be distorted tremendously in the far corner if the spines are kept on the total surface. To overcome this difficulty, a square section of the mesh was kept fixed in time and space.…”

Section: Meshmentioning

confidence: 99%

“…A critical observation in recent years has been the recognition that LPS systems largely distort after densification. [2,3] Accordingly, it is appropriate to treat the problem as a viscous flow process involving the semisolid mixture of solid grains in a liquid phase. In this article, a finite-element approach is used to solve continuity and momentum equations for predicting distortion during LPS for low dihedral angle materials and after full densification.…”

Section: Introductionmentioning

confidence: 99%

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Modeling of distortion after densification during liquid-phase sintering

Binet

Lencoski

Heaney

et al. 2004

Metall Mater Trans A

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Liquid-phase sintering (LPS) is a technique widely used to sinter hard and heavy metals such as tungsten carbide and tungsten heavy alloys. LPS involves formation of a liquid phase during sintering that promotes fast densification. However, the ratio of liquid to solid, microstructure and external forces (gravity, component/substrate friction) act to promote distortion as a function of sintering time and temperature. To understand and control distortion during LPS, a numerical model is being developed to solve continuity and momentum equations using a finite-element technique. In this article, transient distortion under gravity is calculated as a function of surface tension, density, and viscosity of the material. The effect of the friction force due to the component support during isothermal sintering is also evaluated and compared with experimental data acquired by in-situ recording of distortion during sintering.

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Section: A Equationsmentioning

confidence: 54%

Section: Meshmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Modeling of distortion after densification during liquid-phase sintering

Binet

Lencoski

Heaney

et al. 2004

Metall Mater Trans A

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“…[5,7,8] The Al-7Zn-2.5Mg-1Cu alloy studied does not contain liquid and solid phases with significantly different densities. Hence, gravity-induced distortion can be excluded.…”

Section: Discussionmentioning

confidence: 99%

“…[1,3] This is affected by a variety of factors including inhomogeneous green density distribution, [4,5] large density difference between the liquid phase and solid phase, [6,7] uneven temperature distribution in parts during sintering, [8] and cooling rates from the sintering temperature. [5] On the other hand, factors such as a high liquid fraction or the use of a fast heating rate may not always cause distortion.…”

Section: Introductionmentioning

confidence: 99%

Distortion in a 7xxx Aluminum Alloy during Liquid Phase Sintering

Yuan

Huo

Schaffer

et al. 2013

Metall Mater Trans A

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The distortion in a sintered 7xxx aluminum alloy, Al-7Zn-2.5Mg-1Cu (wt. pct), has been investigated by sintering three rectangular bars in each batch at 893 K (620°C) for 0 to 40 minutes in nitrogen, followed by air or furnace cooling. They were placed parallel to each other, equally spaced apart at 2 mm, with their long axes being perpendicular to the incoming nitrogen flow. Pore evolution in each sample during isothermal sintering was examined metallographically. The compositional changes across sample mid-cross section and surface layers were analyzed using energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy depth profiling, respectively. The two outer samples bent toward the middle one, while the middle sample was essentially distortion free after sintering. The distortion in the outer samples was a result of differential shrinkage between their outer and inner surfaces during isothermal sintering. The porous outer surface showed an enrichment of oxygen around the large pores as well as lower magnesium and zinc contents than the interior and inner surface of the same sample, while the inner surface was distinguished by the presence of AlN. The differential shrinkage was caused by different oxygen contents in local sintering atmosphere and unbalanced loss of magnesium and zinc between the outer and inner surfaces.

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