Plastic Deformation in Metal Powder Compaction

Hewitt, R.; Wallace, W.E.; Malherbe, Magali

doi:10.1179/pom.1974.17.33.001

Cited by 51 publications

(25 citation statements)

References 4 publications

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“…In our case due to the high degree of contact fixing (0.965 and 0.978 with a pressing pressure of 600 and 800 MPa, respectively) and use of a rigid die there is no removal of oxide films from the deformation zone. The tangential component of stresses promoting renewal of the surface and leading to an increase in strength [37] is at a minimum. Apparently in the cases described in [38][39][40][41] for obtaining high strength with cold compaction of spherical powders the metal contact was formed due to creation of special compaction conditions.…”

Section: Discussion Of the Experimentsmentioning

confidence: 99%

Mechanical properties of green compacts. II. Effect of powder relative bulk density on the strength of compacts with different forming temperature conditions

Radchenko

2004

Powder Metall Met Ceram

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621.762 Mechanisms of strength for green compacts made from powders of iron, nickel and its alloys, copper, tin, and zinc are analyzed. The strength of green compacts prepared from metal powders of medium fineness with a relative bulk density (RBD) from 0.119 to 0.568 by two-way compaction in rigid dies with homologous temperatures from 0.15 to 0.59 (pressure from 200 to 800 MPa, powder deformation rate 10 −2 -10 −3 m/sec) is studied. Compact strength is determined by diametric compression of cylindrical compacts. The dependence of strength on compact porosity is studied by the Bal'shin equation. The possibility is demonstrated of using this relationship in order to describe hot compaction and formally describe cold compaction of powders with RBD up to 0.40. The effect of homologous temperature and powder RBD on compact strength is determined. The homologous temperature for transition from warm to hot compaction and the effect of compact density (degree of deformation) on this temperature is studied. It is shown that linear approximation is possible for the dependence of compact strength on powder RBD according to the equation σ f.c = 87-217⋅RBD.

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Section: Discussion Of the Experimentsmentioning

confidence: 99%

Mechanical properties of green compacts. II. Effect of powder relative bulk density on the strength of compacts with different forming temperature conditions

Radchenko

2004

Powder Metall Met Ceram

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“…Even though it is widely agreed that compaction is a multi stage process, [27][28][29] most mathematical models (including Eq. [7]) really only represent two stages-an initial density and then the compaction caused by the applied load.…”

Section: B Compactionmentioning

confidence: 99%

Compaction of Titanium Powders

Gerdemann

Jablonski

2010

Metall Mater Trans A

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Accurate modeling of powder densification has been an area of active research for more than 60 years. The earliest efforts were focused on linearization of the data because computers were not readily available to assist with curve-fitting methods. In this work, eight different titanium powders (three different sizes of sponge fines <150 lm, <75 lm, and < 45 lm; two different sizes of a hydride-dehydride [HDH]<75 lm and<45 lm; an atomized powder; a commercially pure [CP] Ti powder from International Titanium Powder [ITP]; and a Ti 6 4 alloy powder) were cold pressed in a single-acting die instrumented to collect stress and deformation data during compaction. From these data, the density of each compact was calculated and then plotted as a function of pressure. The results show that densification of all the powders, regardless of particle size, shape, or chemistry, can be modeled accurately as the sum of an initial density plus the sum of a rearrangement term and a work-hardening term. These last two terms are found to be a function of applied pressure and take the form of an exponential rise.

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“…The interpretation of low-pressure, nonlinear portion of the Heckel plot has been controversial. Hewitt et al (1974) argue that plastic deformation occurs at points of stress concentration in the low-pressure region and that the pressure at which the curve becomes linear corresponds to a transition from local to homogeneous plastic flow. A third, nonlinear region at higher pressures is sometimes observed (e.g., Kurt and Davies, 1996).…”

Section: Heckel Analysismentioning

confidence: 99%