Al-Co alloys is an emerging category of metallic materials with promising properties and potential application in various demanding environments. Over the years, different manufacturing techniques have been employed to fabricate Al-Co alloys, spanning from conventional casting to rapid solidification techniques, such as melt spinning, thus leading to a variety of different microstructural features. The effect of the fabrication method on the microstructure is crucial, affecting the morphology and volume of the precipitates, the formation of supersaturated solid solutions and the development of amorphous phases. In addition, the alloy composition has an effect on the type and volume fraction of intermetallic phases formed. As a result, alloy properties are largely affected by the microstructural outcomes. This review focuses on highlighting the effect of the fabrication techniques and composition on the microstructure and properties of Al-Co alloys. Another goal is to highlight areas in the field that are not well understood. The advantages and limitations of this less common category of Al alloys are being discussed with the scope of future prospects and potential applications.

/pdf/a-critical-review-on-al-co-alloys-fabrication-routes-1fe9c6ml.pdf

A Critical Review on Al-Co Alloys: Fabrication Routes, Microstructural Evolution and Properties

The present work compares WC-10Co-4Cr coatings fabricated by HVOF spraying of a conventional powder (1.33 ± 0.67 μm) and a nanostructured powder (0.17 ± 0.06 μm) on Al7075-T6, in terms of microstructure and phase composition, microhardness and fracture toughness, corrosion performance in 3.5 wt% NaCl (potentiodynamic polarization, chronoamperometry, galvanic effect measurements and salt spraying) and sliding wear performance under lubrication. Τhe nanocoating, despite its greater microporosity and decarburization, displayed higher microhardness, fracture toughness and surface roughness compared to its conventional counterpart. A superiority of the corrosion behaviour and sliding wear behaviour of the nanocoating as compared to its conventional analogue was observed in terms of a higher resistance to general/localized corrosion, lower passive film conductivity, lower wear rate, subtler wear scars and greater occurrence of islands of tribofilms. The reasons for such superiority are being clarified. A good galvanic compatibility between the nanocoating and its substrate was manifested. Both coatings exhibited high corrosion resistance during salt spraying for 45 days. The mechanisms of corrosion and wear degradation are being proposed. 

Corrosion and wear of coatings fabricated by HVOF-spraying of nanostructured and conventional WC–10Co-4Cr powders on Al7075-T6

Enhanced Elevated-Temperature Tribological Properties and Microstructure of Co-continuous Iron Foam/SiC/Al-Si Dual-Reinforced Composites Fabricated by Vacuum-Assisted Infiltration

The A359-SiCp/Fe interpenetrating phase composites reinforced with three-dimensional network structure iron foam and 20 wt. % SiC particles were fabricated after the infiltration technique by using the newly developed vacuum assisted infiltration procedures. The dry-sliding tribological behavior of A359-SiCp/Fe composites was investigated using the HT-1000 ball-on-disc type high temperature tribometer. The samples were subjected to a variety of temperatures and applied loads to investigate the influence on the wear rate and friction coefficient. In this study, SEM was used to analyses the wear microscopic morphology of A359-SiCp/Fe composites reinforced by iron foam. The wear longitudinal section and the morphology of the wear debris were analyzed by EDS and determined to explore the high-temperature wear mechanism under different temperatures and loads. Hardness analysis from the outer periphery to the core revealed an improvement in hardness. The hardness distribution of the wear longitudinal section is different at different temperatures. The formation of a high-hardness mechanical mixed layer with a different thickness on the wear surface can effectively reduce the wear rate. Microstructural investigations demonstrated that the change in wear debris shape with increasing temperature is mostly related to the change in wear mechanism. Abrasive wear and oxidation wear are the main wear mechanisms. With an increase in temperature and plastic deformation, delamination and adhesion are the predominant wear mechanisms, accompanied by the additional oxidative wear.

A. Kanderakis

Papers

Sliding wear performance of Al–Co alloys fabricated by vacuum arc melting and correlation with their microstructure