Behaviour of metal powders during cold and warm compaction
TL;DR: In this article, an instrumented die was used to investigate the behavior of metal powders during cold (ambienttemperature) and warm (up to 140°C) compaction.
Abstract: An instrumented die was used to investigate the behaviour of metal powders during cold (ambienttemperature) and warm (up to 140°C) compaction. This instrument enables simultaneousmeasurement of density, die wall friction coefficient, the triaxial stresses acting on the powderduring the course of compaction and ejection pressure. Commercial iron, titanium, aluminium,316L stainless steel (SS) and aluminium–silicon powders were employed for investigation. Theresults demonstrated the advantages of powder preheating on the compaction behaviour of metalpowders concerning green density, dimensional changes, frictional behaviour, ejectioncharacteristics and compactibility. However, the outlines also determined that the response ofthe non-ferrous powders to powder preheating is somehow different from those of the ferrouspowders. In this context, the behaviour of prealloy aluminium–silicon powders during compactionwas found of particular interest, as their compactibility is strongly affected by powder prehe...
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25 Apr 2007-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the effect of reinforcement nanoparticles on the compressibility of aluminum powder was examined in uniaxial compaction in a rigid die and it was shown that at the early stage of compaction when the rearrangement of particles is the dominant mechanism of the densification, disintegration of the nanoparticle clusters and agglomerates under the applied load contributes in the density of composite powder prepared by blending method.
Abstract: The densification response of aluminum powder reinforced with 5 vol.% nanometric alumina particles (35 nm) during uniaxial compaction in a rigid die was studied. The composite powder was prepared by blending and mechanical milling procedures. To determine the effect of the reinforcement nanoparticles on the compressibility of aluminum powder, monolithic Al powder, i.e. without the addition of alumina, was also examined. It was shown that at the early stage of compaction when the rearrangement of particles is the dominant mechanism of the densification, disintegration of the nanoparticle clusters and agglomerates under the applied load contributes in the densification of the composite powder prepared by blending method. As the compaction pressure increases, however, the load partitioning effect of the nanoparticles decreases the densification rate of the powder mixture, resulting in a lower density compared to the monolithic aluminum. It was also shown that mechanical milling significantly impacts the compressibility of the unreinforced and reinforced aluminum powders. Morphological changes of the particles upon milling increase the contribution of particle rearrangement in densification whilst the plastic deformation mechanism is significantly retarded due to the work-hardening effect of the milling process. Meanwhile, the distribution of alumina nanoparticles is improved by mechanical milling, which in fact, affects the compressibility of the composite powder. This paper addresses the effect of mechanical milling and reinforcement nanoparticles on the compressibility of aluminum powder.
150 citations
TL;DR: In this paper, a set of low cost beta alloys with the composition Ti-7Fe, processed by conventional powder metallurgy (PM), were prepared by conventional blending of elemental Ti hydride-dehydride powder with three different Fe powder additions: water atomised Fe, Fe carbonyl and master alloy Fe-25Ti.
Abstract: This work studies a set of low cost beta alloys with the composition Ti–7Fe, processed by conventional powder metallurgy (PM). The materials were prepared by conventional blending of elemental Ti hydride–dehydride powder with three different Fe powder additions: water atomised Fe, Fe carbonyl and master alloy Fe–25Ti. The optimal sintering behaviour and the best mechanical properties were attained with the use of Fe carbonyl powder, which reached a sintered density of up to 93% of the theoretical density, with UTS values of 800 MPa in the ‘as sintered’ condition. Coarse water atomised powder particles promoted reactive sintering, and coarse porosity was found due to the coalescence of Kirkendall porosity and by the pores generated during the exothermic reaction between Ti and Fe. The addition of Fe–25Ti produced brittle materials, as its low purity (91·5%) was found to be unsuitable for formulating Ti alloys.
65 citations
TL;DR: In this paper, the compressibility behavior of Al-SiC nanocomposite powders was examined and the density-pressure data were analyzed by linear and non-linear compaction equations.
65 citations
TL;DR: In this paper, the authors present a systematic and critical analysis of the current scientific knowledge about fatigue and fracture properties of titanium alloys manufactured via powder-based methods, and demonstrate that, through appropriate manufacturing technology and parameters selection, titanium alloy with similar or improved properties can be achieved by means of more cost-effective powderbased processes rather than via ingot metallurgy.
48 citations
01 Jan 2011
TL;DR: In this paper, an overview of the PM process in general and sintering in particular is provided, including the roles of magnesium and the atmosphere on sinter and how these factors affect densification and the microstructure.
Abstract: Conventional press and sinter aluminium powder metallurgy is a well-developed, cost-effective process for net-shaped fabrication of complex parts via die compaction and sintering. This chapter provides an overview of the PM process in general and sintering in particular. Key issues in the PM processing of aluminium are considered, including the roles of magnesium and the atmosphere on sintering and how these factors affect densification and the microstructure.
39 citations
References
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Book•
01 Jan 1996
TL;DR: Sintering Measurement Techniques Solid-State Sintering Fundamentals as discussed by the authors Microstructure and Processing Relations in Solid-state Sinterings, Mixed Powders, Pressure-Assisted SinterING.
Abstract: Sintering Measurement Techniques. Solid-State Sintering Fundamentals. Microstructure and Processing Relations in Solid-State Sintering. Solid-State Sintering of Mixed Powders. Liquid-Phase Sintering. Pressure-Assisted Sintering. Novel Sintering Techniques. Sintering Atmospheres. Sintering Practice. Future Directions. Appendix. Index.
2,261 citations
TL;DR: In this article, it is shown mathematically that if a pressure dependent term is used in the Heckel equation then the resulting modified equation is very similar to the Kawakita one and, in fact, becomes identical in form for a particular value of the pressure dependency term.
297 citations
TL;DR: In this article, the role of die wall lubrication procedure on the consolidation behavior of metallic powders and subsequent microstructural development during sintering was investigated, and it was found that the lubricant procedure has a great influence on consolidation and micro-structural features of the materials investigated.
58 citations
TL;DR: The science of materials indicates that the compressibility of metal powders decreases as yield strength increases as discussed by the authors, and in heated powder mixes the yield strength drops and an effective lubrication mech...
Abstract: The science of materials indicates that the compressibility of metal powders decreases as yield strength increases. In heated powder mixes the yield strength drops and an effective lubrication mech...
45 citations
TL;DR: In this paper, the powder metallurgy (PM) technology was used to eliminate segregation and reduce the number of processing steps for TiAl alloys, which has excellent properties and oxidation resistance and is therefore being targeted as replacements for conventional Ti alloys and Ni-based super alloys in applications such as aircraft turbines and automotive engines.
26 citations