Particle growth by coalescence during liquid phase sintering of Fe-Cu

Kaysser, W. A.; Takajo, Shigeaki; Petzow, G.

doi:10.1016/0001-6160(84)90208-6

Cited by 75 publications

(28 citation statements)

References 8 publications

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“…Grain agglomeration is inherent to LPS, even in dilute systems [85]. Accordingly, coalescence must be included in the grain size distribution models [86]. Another problem relates to the assumed diffusion field around each grain [87].…”

Section: Grain Size Distributionmentioning

confidence: 99%

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Review: liquid phase sintering

2009

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Liquid phase sintering (LPS) is a process for forming high performance, multiple-phase components from powders. It involves sintering under conditions where solid grains coexist with a wetting liquid. Many variants of LPS are applied to a wide range of engineering materials. Example applications for this technology are found in automobile engine connecting rods and high-speed metal cutting inserts. Scientific advances in understanding LPS began in the 1950s. The resulting quantitative process models are now embedded in computer simulations to enable predictions of the sintered component dimensions, microstructure, and properties. However, there are remaining areas in need of research attention. This LPS review, based on over 2,500 publications, outlines what happens when mixed powders are heated to the LPS temperature, with a focus on the densification and microstructure evolution events.

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Section: Grain Size Distributionmentioning

confidence: 99%

“…The neck size divided by the larger grain size decreases as the grains differ in size, while the neck size normalized by the smaller grain size increases. A curved grain boundary provides a driving force for grain coalescence [86]. Fig.…”

Section: Neck Growthmentioning

confidence: 99%

Review: liquid phase sintering

2009

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Section: First Alloying Elementsmentioning

confidence: 99%

“…This phenomenon have been widely studied in different works [16,17,18]. The use of copper at industrial level in sintered steels and all the problems linked with the transient liquid phase, boosted several fundamental studies associated with this kind of sintering option [19,20,21,22,23,24,25].The second important alloying element widely used in PM steels was nickel [26,27]. Nickel has, like Cu and compared with Fe, a low oxygen affinity, but it poor diffusivity in iron requieres the use of high sintering temperatures or long sintering times to get a proper diffusion into iron.…”

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confidence: 99%

From Sintered Iron to High Performance PM Steels

Torralba

Oro

Campos

2011

MSF

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Keywords: powder metallurgy steels, low alloyed steels, high performance, master alloys.Abstract. Since low alloyed sintered steels were introduced in the market of the structural parts, we have followed the evolution of a material with poor mechanical properties and any uniformity (in the sense of reproducibility) to materials that today are produced with high reliability and performance. The working efficiency could be equivalent in many cases with the best wrought steel, and maintaining a good margin in terms of cost and competitively. In this paper a complete review of the topic is accomplished, from the early times when the first parts were made by plain iron or iron-carbon, going through the different alloying systems: Fe-Cu, Fe-P, Fe-Cu-Ni-Mo, and more recently Fe-Cr-Mo and Fe-Mn. The development in processing routes has been considered too. The main milestones in the field of new alloying systems have been: 1) the introduction of Cu in 60-70"s, 2) the new complex systems with Cu-Ni-Mo in the 80"s and 3) the introduction of alloying elements with high oxygen affinity (in the late 90"s). Regarding the milestones in processing could be considered: 1) the development of new mixing procedures, 2) the warm compaction and high velocity compaction, 3) the improvements in sintering control and high temperature sintering. Several decades of research and innovation, acting on the processing system (mixing, pressing, sintering, post-sintering operations,…) and on the alloying system (from the earliest times with plain iron to complex systems used today), has allowed us to have a highly competitive materials, in terms of performance, and processes in terms of cost. The future is still open to new developments. First sintered steels.Iron based powder metallurgy (PM), were developed in the previous years to the II World War, being the absence of raw materials the pushing effect, and it was the origin of a new materials family (PM Steels) that today can be considered a high performance materials. The first sintered part was introduced in the car industry by General Motors in 1937 and was an oil gear for oil pump [1]. One of the first components introduced was one iron part for an electrical engine in 1945 [2].Till late 60"s were manufactured by PM simple parts, that were based on Fe-C and Fe-Cu-C systems. The knowledge of these systems was developed from works that analyze the possible formation of liquid phase during sintering with the aim of improving the densification and to promote sintering activation [3] as well the diffusion mechanisms in plain systems and selfdiffusion of Fe [4,5]. To analyze and to understand the sintering steps were use iron wires that can reproduce the sintering model based on spheres [6].Looking for the improvement in the mechanical properties, at that time considering the available technology two basic requirements for new alloying systems were stated: poor or null affinity for the oxygen -sintering atmospheres were not enough dried [7]-and the possibility of controlling dimensionally the s...

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“…Although theories of coalescence are not clearly established, experimental evidences and existing theories predict that in materials that tend to exhibit strong anisotropy in grain boundary 4 (GB) energies, coalescence may occur between contiguous grains with low GB misorientation angles [7,8].…”

Section: Introductionmentioning

confidence: 99%

The influence of Si on the microstructure and sintering behavior of ultrafine WC

Kumar

Watabe

Kurokawa

2012

Philosophical Magazine

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The microstructure of sintered nano scale tungsten carbide powders with 1wt. % Si addition was found to be populated by an abnormally large number of elongated grains. Interrupted sintering experiments were conducted to clarify the origins of the excessive abnormal grain growth seen in the microstructure. It was observed that rapid coarsening occurred at high temperatures owing to the formation of a liquid phase. However, the grain shape evolution during this coarsening period was found to be a consequence of excessive stacking faults and micro twins on the basal planes probably generated by reaction of WC with Si. Analyses of the microstructures and the isothermal and non isothermal coarsening behaviors suggested that the platelet morphology evolved by defect-assisted nucleation and growth on faceted grains. Based on experimental evidence from samples interrupted at low temperatures and crystal growth theories, we discuss the possible mechanisms that eventually led to the rampant platelet-type morphology. Further, the influence of such rapid grain growth on the shrinkage rate during sintering is also discussed. In comparison with the cyclic coarsening-densification process of sintering in pure nano scale WC, the addition of Si leads to only two distinct sintering stages: either densification dominated or coarsening dominated. Concurrent densification and coarsening cannot be sustained particularly in the presence of a liquid phase that significantly enhances coarsening.

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Particle growth by coalescence during liquid phase sintering of Fe-Cu

Cited by 75 publications

References 8 publications

Review: liquid phase sintering

Review: liquid phase sintering

From Sintered Iron to High Performance PM Steels

The influence of Si on the microstructure and sintering behavior of ultrafine WC

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