IN view of the interest attaching to the vaporisation and diffusion of solids, the following observations may be worthy of record.

The Diffusion of Solids

Emerging trends in manufacturing such as light weighting, increased performance and functionality increases the use of multi-material, hybrid structures and thus the need for joining of dissimilar materials. The properties of the different materials are jointly utilised to achieve product performance. The joining processes can, on the other hand be challenging due to the same different properties. This paper reviews and summarizes state of the art research in joining dissimilar materials. Current and emerging joining technologies are reviewed according to the mechanisms of joint formation, i.e.; mechanical, chemical, thermal, or hybrid processes. Methods for process selection are described and future challenges for research on joining dissimilar materials are summarized.

/pdf/joining-of-dissimilar-materials-5d5ghi3lwg.pdf

Joining of dissimilar materials

Binder Jet printing is an additive manufacturing technique that dispenses liquid binding agent on powder to form a two-dimensional pattern on a layer. The layers are stacked to build a physical article. Binder Jetting (BJ) can be adapted to almost any powder with high production rates and the BJ process utilizes a broad range of technologies including printing tehniques, powder deposition, dynamic binder/powder interaction, and post-processing methods. A wide variety of materials including polymers, metals, and ceramics have been processed successfully with Binder Jet. However, developing printing and post-processing methods that maximize part performance is a remaining challenge. This article presents a broad review of technologies and approaches that have been applied in Binder Jet printing and points towards opportunities for future advancement.

Binder jetting: A review of process, materials, and methods

The sintering mechanism in spark plasma sintering – Proof of the occurrence of spark discharge

Metal matrix nanocomposites (MMNCs) are thosemetal matrix composites where the reinforcement is of nanometer dimensions, typically less than 100nm in size. Also, it is possible to have both the matrix and reinforcement phases of nanometer dimensions. The improvement in mechanical properties of MMNCs is attributed to the size and strength of the reinforcement as well as to the fine grain size of the matrix. Spark plasma sintering has been used extensively over the past years to consolidate wide range of materials including nanocomposites and was shown to be effective noneconventional sintering method for obtaining fully dense materials with preserved nanostructure features. The objective of this work is to briefly present the spark plasma sintering process and review published work on spark-plasma-sintered metals and metal matrix nanocomposites.

/pdf/spark-plasma-sintering-of-metals-and-metal-matrix-o3n6to3uee.pdf

Spark plasma sintering of metals and metal matrix nanocomposites: a review

Densification mechanisms in spark plasma sintering: Effect of particle size and pressure

Effect of sintering temperature on the microstructure and mechanical properties of Fe–30%Ni alloys produced by spark plasma sintering

Effect of starting powder particle size and heating rate on spark plasma sintering of Fe-Ni alloys

Mixed 93W–4.9Ni–2.1Fe powders were sintered via the spark plasma sintering (SPS) and hybrid spark plasma sintering (HSPS) techniques with 30 mm and 60 mm samples in both conditions. After SPS and HSPS, the 30 mm and 60 mm alloys (except 60 mm-SPS) had a relative density (> 99.2%) close to the theoretical density. Phase, microstructure and mechanical properties evolution of W–Ni–Fe alloy during SPS and HSPS were studied. The microstructural evolution of the 60 mm alloys varied from the edge of the sample to the core of the sample. Results show that the grain size and the hardness vary considerable from the edge to the core of sintered sample of 60 mm sintered using conventional SPS compared to hybrid SPS. Similarly, the hardness also increased from the edge to the core. Furthermore, the 60 mm-HSPS alloy exhibited improved bending strength of 1115 MPa when compared to that of 60 mm-SPS, 920 MPa. The intergranular fracture along the W/W grain boundary is the main fracture modes of W–Ni–Fe, however in the 60 mm-SPS alloy peeling of the grains was also observed which diminished the properties. The mechanical properties of SPS and HSPS 93W–4.9Ni–2.1Fe heavy alloys are dependent on the microstructural parameters such as tungsten grain size and overall homogeneity.

A comparative study of spark plasma sintering and hybrid spark plasma sintering of 93W–4.9Ni–2.1Fe heavy alloy

The effect of particle size on the densification mechanism of as atomised copper powder during spark plasma sintering was investigated. In the temperature range 600–700°C and pressure range 20–30 MPa, consolidation of the powders is given by rearrangement, deformation, neck formation and minimal growth. Deformation and neck formation are enhanced by an increase in the particle size, since the current flow in the contact areas increases with the particle size. The actual pressure in the contact area, instead, does not change with the particle size. The extremely high and localised temperature on the contact points between particles leads to melting, giving rise to neck formation. The high temperature decreases towards the centre of the particle, allowing thermal softening and increasing the deformability of the particle core.

S. Diouf

Papers

Densification mechanisms in spark plasma sintering: Effect of particle size and pressure

Effect of sintering temperature on the microstructure and mechanical properties of Fe–30%Ni alloys produced by spark plasma sintering

Effect of starting powder particle size and heating rate on spark plasma sintering of Fe-Ni alloys

A comparative study of spark plasma sintering and hybrid spark plasma sintering of 93W–4.9Ni–2.1Fe heavy alloy

Study of effect of particle size on densification of copper during spark plasma sintering