Influence of the Electrolyte Composition on the Corrosion Behavior of Anodized AZ31B Magnesium Alloy

Investigations have been performed to study the effects of the electrolyte composition on the properties of anodized films grown on AZ31B magnesium alloy. The corrosion protection ability of the oxide layers was explored by using potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy. Film morphology was examined by scanning electron microscopy and confocal laser scanning microscopy. In spite of its higher roughness average, the film formed in the silicate and hydroxide mixed solution enhanced the protective properties of the anodized layer, thus reducing the substrate dissolution rate.

High Temperature Solid-Liquid Interactions in Metal-Ceramic Brazing: A Critical Review

Solid-liquid interactions in metal-ceramic systems are extremely important in high temperature brazing processes. These interfacial phenomena are reviewed here, from both the thermodynamic and microstructural viewpoints. At high temperature, the wetting characteristics and the adhesion properties of the joints are strongly related to the high atomic mobility of the different phases, giving rise to different phenomena, ranging from the dissolution of the ceramic in the liquid phase, reactions, formation of new phases and reprecipitation at the solid-liquid interface. The role phase diagrams in guiding the choice of the filler alloys composition and to optimize the brazing procedures is emphasized. In particular, it is shown that the computation of new diagrams and the critical use of the existing ones is essential to understand how to suppress the substrate dissolution and to interpret the evolution of the system. Experimental data are presented and discussed concerning the interactions between liquid metals with early-transition-metal diborides (TiB2, ZrB2, HfB2) as a typical example involving the joining of Ultra-High Temperature Ceramics (UHTCs). Overall, these studies represent the basic step linking the chemical and structural information to the design of industrial processes involving a liquid phase at high temperature, such as the production of metal-ceramic joints or composite materials to be used in highly demanding applications.

Thermodynamic Prediction Of The Diffusion Barrier Morphology In The Al/Ni – Nano-Foil Designed For The Self-Propagating Reaction

Thermodynamic model for the diffusion barrier formation in the Al/Ni nano-foil is presented. Two types of diffusion are distinguished in the model, boundary diffusion for substrate dissolution and bulk diffusion for solidification. The creation of two phases: Al3Ni, Al3Ni2in the diffusion barrier are predicted due to the cyclical manner of the dissolution and solidification occurrence.

Intermetallic formation induced substrate dissolution in electroless Ni(P)-solder interconnections

The effect of minor transition metal (TM) additives of Ni, Co, or Zn on the interfacial reactions of the solder joints between Sn–Ag–Cu (SAC) solder and the Cu/Ni(P)/Au substrate was investigated, especially subsequent to multi-reflowing. (Cu,Ni)6Sn5 formed at the interface of all the joints except that of SAC–Ni, of which the interfacial compound was (Ni,Cu)6Sn5. The interfacial compounds of the SAC–Co and SAC–Zn contained a small amount of alloying elements of less than 3 at.%. Two P-rich layers, Ni3P and Ni–Sn–P emerged at the interface of the SAC joints. Nanoindentation analysis indicates that the hardness and Young’s modulus of these two phases were slightly higher than those of the Ni(P) substrate, which were in turn much greater than those of the Cu–Ni–Sn compounds. Worthy of notice is that with TM additions, the Ni–Sn–P phase between Ni3P and interfacial compounds was absent even after 10 reflows. For the SAC–Co joints, the growth of Ni-containing intermetallic compounds within the solder gave rise to the excess Ni dissolution, which caused a discrete Ni3P layer and over-consumed Ni(P) substrate underneath the grooves in-between (Cu, Ni)6Sn5 scallop grains at the interface. This phenomenon is presented for the first time, and the mechanism is proposed in this study.