Abstract
The initial microstructure and mechanical properties of composite powders have a vital role in determining the microstructure and mechanical properties of the subsequent consolidated bulk composites. In this work, Al-based matrix composite powders with a dense and uniform distribution of metallic glass nanoparticles were obtained by high-energy milling. The results show that high-energy milling is an effective method for varying the microstructure and mechanical properties of the composite powders, thereby offering the ability to control the final microstructure and properties of the bulk composites. It was found that the composite powders show a deformed layer combined with an undeformed core after milling. The reinforcements, metallic glass microparticles, are fractured into dense distributed nanoparticles in the deformed layer, owing to the severe plastic deformation, while in the undeformed core, the metallic glass microparticles are maintained. Therefore, a bimodal structure was obtained, showing a mechanical bimodal structure that has much higher hardness in the outer layer than the center core. The hardness of the composite particles increases significantly with increasing milling time, due to dispersion strengthening and work hardening.
Highlights
Al-based metal matrix composites (AMMCs) have low density, high specific strength, and high specific stiffness [1,2,3,4,5]; they have been considered preferentially as an ideal engineering material for lightweight applications in the aerospace, defense and automotive industries [6,7]
AMMCs usually show high strength, but limited ductility, due to the defects that exist in the AMMCs, where cracks and premature failure occur [8]
A 5 nm thickness interdifussion interface layer exists in the Zr-based metallic glass (MG) short fiber reinforced Al7075 alloy, and no detrimental intermetallic compounds formed, which is helpful for avoiding crack origination near the interface, and improving strength and ductility [1]
Summary
Al-based metal matrix composites (AMMCs) have low density, high specific strength, and high specific stiffness [1,2,3,4,5]; they have been considered preferentially as an ideal engineering material for lightweight applications in the aerospace, defense and automotive industries [6,7]. There are several typical defects that occur in the most common AMMCs (ceramics as reinforcements), such as agglomeration, porosity, and detrimental interfacial reactions, which severely limits their wider application [9,10,11] To avoid these defects, non-ceramic reinforcements have been developed, such as metallic glass [12,13,14,15,16], quasicrystalline [17], TNM Ti-Al alloy [18] etc. Owing to the difficulty of obtaining MG nanoparticles, preliminary works have mostly focused on micro-sized particle (>5 μm) reinforcing composites, and research on nano-sized metallic glass reinforcements has only rarely been performed [12,15]. A powder metallurgical route was developed to fabricate nanocomposite powder where MG nanoparticles are uniformly distributed in the Al alloy matrix, which may be beneficial for designing and fabricating the novel nanocomposites reinforced with metallic glass nanoparticles
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