Diamond reinforced Al-based bulk metallic glassy composites with improved plasticity fabricated by cold hydro-mechanical pressing

Highlights

• Diamond enhanced Al-based glassy composite is obtained by novel consolidated method.

• The consolidated bulk samples have high strength and room-temperature plasticity.

• A gear-like part is also fabricated by the near-net-shape forming technique.

Abstract

Diamond reinforced Al-based metallic glassy composites with high strength and improved plasticity were fabricated using a novel cold hydro-mechanical pressing (CHMP) of Al₈₅Ni₁₀Ce₅ glassy/nanocrystalline powders. The glassy microstructure was retained after consolidation at room temperature and the strong bonding caused by severe deformation between the particles was responsible for excellent mechanical property of the bulk composites. Furthermore, an Al-based glassy alloy composite gear part was obtained due to the advantage of near-net-shape forming for CHMP. The experimental results suggest that Al-based metallic glasses/composites prepared by CHMP have engineering application potentials.

Introduction

Metallic glasses (MGs) have been considered as advanced structural and functional materials due to the excellent properties when compared with conventional crystalline counterparts [1], [2], [3]. Among MGs-forming systems, Al-based MGs are particularly attractive because of their exceptionally high specific strength, which is about twice as high as that for crystalline Al alloys [4], [5]. However, the high strength is mainly achieved for small pieces of ribbon samples because the glass-forming ability (GFA) of Al-based MGs is relatively low and the maximum size scale is limited [6]. This size limitation further hinders widespread engineering applications of the Al-based MGs. To achieve Al-based MGs in bulk form, tremendous attempts have been dedicated [7], [8], [9] and powder metallurgy (PM) is considered as a simple and efficient technique for fabricating large-sized Al-based MGs and their composites with superior properties [10], [11], [12], [13]. To obtain remarkable properties, consolidating glassy alloy powders into full-dense and bulk samples needs to retain the glassy or partially glassy microstructure after compaction. It is well documented that the glassy powders are consolidated into large dimensions and complex shapes in the supercooled liquid region using conventional methods such as hot pressing [14] and spark plasma sintering [15]. Nevertheless, due to the poor thermal stability of Al-based metallic glassy powders and difficulty in simultaneously controlling temperature precision, the crystallization of glassy phase can occur at high temperature during consolidation [16], [17]. Consequently, it is necessary to utilize a low temperature strategy to produce bulk Al-based MGs/composites with large size and promising property. Recently, the high pressure technique has been developed to consolidate Al-based amorphous/nanocrystalline powders into bulk samples with high density [18], [19]. Moreover, a novel CHMP method that combines the triaxial compression principle and high pressure technology has been proposed [20].

Although the high strength of the consolidated Al-based glassy/nanocrystalline alloys can be obtained, their plastic deformation at room temperature is rather poor [15]. To improve the plasticity, it is noteworthy that various metallic glassy matrix composites show greater room temperature plasticity compared with monolithic MGs [21], [22], [23]. Especially, large-sized ultrahigh strength bulk metallic glassy matrix composites with enhanced plasticity were fabricated using PM route [24]. Furthermore, diamond-reinforced metallic glassy composites with improved properties have been developed [25], [26]. Based on the above demonstrations, it is expected that the diamond particles can be introduced to fabricate Al-based bulk metallic glassy composites for improving their strength and/or plasticity.

In this work, the in situ formed Al-based glassy/nanocrystalline powders were used as the precursors. Diamond-reinforced Al-based bulk composites with high strength and large plasticity were successfully consolidated using the CHMP technique at room temperature. In addition, a gear-like part was also fabricated by the near-net-shape forming method, which may contribute to the applications of Al-based metallic glassy composites under certain applicable condition.