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Complex liquid–solid reactions occur during brazing. A deep understanding of brazing liquid evolution is therefore of important concern for the bonding between filler and substrates. The joining of gas‐pressure‐sintered silicon nitride (Si3N4) ceramic to oxygen‐free copper (OFC) foil was prepared using Ag–Cu–TiH2 filler at 875°C for 0.5 h. The effect of the Ag:Cu ratio on the interfacial microstructure and peeling strength of the joints was analyzed. The reaction of brazing liquid with Si3N4 ceramic includes reactions with both the β‐Si3N4 and the grain boundary phases (Y–Si–Mg–O–N). The resulting interfacial reaction products include TiN, Ti5Si3, and potential Cu3Ti3O. Based on the phase composition and three‐dimensional morphology of the interfacial reaction products in the Si3N4 ceramic/OFC foil joints, a model for the evolution of the brazing liquid as the reaction proceeds was proposed. Peeling test results indicated that the peeling strength of the joints rises unilaterally with the increase of the Ag:Cu ratio in the filler until reaching the peak value of 24.3 N/mm at the maximum Ag:Cu ratio of 90:10. The mechanisms of the joint peeling fracture were discussed in detail. [ABSTRACT FROM AUTHOR]

The Au-28Ge (at%) eutectic alloy is a high-performance solder with a melting point of 361 °C. However, the brittle interfacial reaction products layer formed between the Au–Ge solder and substrate (Cu or Ni) is always the weak region. Hence, the joint fails at a relatively low shear strength (∼53 MPa). Here, the Cu–Ni alloys (Ni content is 20, 50, or 70 at%) are designed as the substrates to connect with the Au–Ge eutectic at 400 °C. A classic example is represented by the Au–Ge/Cu20Ni joint, which achieves a shear strength of above 100 MPa after soldering at 400 °C for 10–20 min. Microstructure characterization reveals that a face-centered cubic structured solid solution (FCC) layer forms at the Au–Ge/Cu20Ni joint. In contrast, it is mainly the NiGe or Ni2Ge layer in the Au–Ge/Cu50Ni and Au–Ge/Cu70Ni joints. On the one hand, compared to the brittle intermetallic compound products layer, the FCC layer shows adequate ductility, releasing the local strain incompatibility via pronounced local plastic deformation. On the other hand, the fine NiGe and Ni2Ge precipitation and fine grains make the FCC layer stronger than the solder matrix. Therefore, this products layer is no longer the weak region in the solder joint. As a result, the Au–Ge/Cu20Ni joint achieves outstanding shear strength. This study enriches our fundamental understanding of producing ductile phases to enhance the shear strength of the solder joints by designing alloy substrates.

Abstract: Squeeze forming process is a special casting technique that combines the advantages of traditional high pressure die casting, gravity permanent mold die casting and common forging technology. It is a relatively new casting process. It is otherwise called squeeze forming, liquid forging, liquid pressing, extrusion casting, liquid metal stamping, pressure crystallization and corthias casting. The above said process was first discovered by the Russians and later it was developed in countries like USA, Europe and Japan. This advanced casting method is applied for processing of both ferrous and non-ferrous materials besides composites. The major advantages of this technology are elimination of porosity and shrinkage, 100% casting yield, attainment of greater part details, good surface finish, good dimensional accuracy, high strength to weight ratio, improved wear resistance, higher corrosion resistance, higher hardness, resistance to high temperature, improved fatigue and better creep strength. The components manufactured by this casting method requires lesser post machining operation and they have improved mechanical properties like higher strength and ductility. In squeeze casting process the liquid metal is pressurized while they solidify and hence near net shapes can be produced with sound and dense quality. The microstructural refinement of squeeze cast products is desirable for many critical applications. This process is simple, economical and it can be automated easily. The process generates the highest mechanical properties attainable in a cast product. So this process has been adopted to make composite castings at an affordable cost. This paper reviews about the principles of squeeze casting technology, which can be applied to process discontinuous fiber reinforced metal matrix composite castings. Besides this article highlights the type of engineering components produced by this advanced casting method. [Copyright &y& Elsevier]