Abstract
Development of metal matrix composites (MMCs) with metallic glass/amorphous alloy reinforcements is an emerging research field. As reinforcements, metallic glasses with their high strength (up to ~2 GPa) and high elastic strain limit (~2%) can provide superior mechanical properties. Being metallic in nature, the glassy alloys can ensure better interfacial properties when compared to conventional ceramic reinforcements. Given the metastable nature of metallic glasses, lightweight materials such as aluminum (Al) and magnesium (Mg) with relatively lower melting points are suitable matrix materials. Synthesis of these advanced composites is a challenge as selection of processing method and appropriate reinforcement type (which does not allow devitrification of the metallic glass during processing) is important. Non-conventional techniques such as high frequency induction sintering, bidirectional microwave sintering, friction stir processing, accumulative roll-bonding, and spark plasma sintering are being explored to produce these novel materials. In this paper, an overview on the synthesis and properties of aluminum and magnesium based composites with glassy reinforcement produced by various unconventional methods is presented. Evaluation of properties of the produced composites indicate: (i) retention of amorphous state of the reinforcement after processing; (ii) significant improvement in hardness and strength; (iii) improvement/retention of ductility; and (iv) high wear resistance and low coefficient of friction. Further, a comparative understanding of the properties highlights that the selection of the processing method is important in producing high performance composites.
Highlights
Metal matrix composites (MMCs) based on light metals namely Al, Ti, and Mg are developed for aircraft, automotive, sports, and electronics industries due to their light weight and enhanced mechanical properties [1,2,3,4]
Heat is generated by microwaves within materials and radiates outward thereby heating the samples [23]. Given that these two heating processes are distinctly different, in the case of conventional heating, temperatures are found to be higher at the surface than those at the core, and this is vice versa in the case of microwave sintering [23]
Advantages of bi-directional microwave sintering method are: (i) it ensures good wettability between reinforcement and matrix; (ii) it involves rapid heating rate and high sintering temperatures in short duration of time; (iii) it eliminates thermal gradient and provides uniform heating; (iv) it generates low porosity, and (v) it gives rise to fine microstructure and better mechanical properties [23,24]
Summary
Metal matrix composites (MMCs) based on light metals namely Al, Ti, and Mg are developed for aircraft, automotive, sports, and electronics industries due to their light weight and enhanced mechanical properties [1,2,3,4]. Metallic glass reinforced light metal composites are being developed. Metallic glasses are considered as ‘solids with frozen-in liquid structure’ and are meta-stable thermodynamically These materials possess high strength (~2 GPa), high elastic limit of. With distinctly different structure and properties compared to conventional crystalline materials, metallic glasses are currently being explored as reinforcements for light metal matrices. As they can provide metal–metal bonding at interface with less thermal mismatch, they can serve as better alternatives to conventional ceramic reinforcements [17,18]. Different methods of processing Al/Mg MMCs with metallic glass reinforcements, examples of composites made, their microstructure and mechanical properties are presented
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