High performance cutting of Zr-based bulk metallic glass: a review of chip formation

Zr-based bulk metallic glass (Zr-based BMG) has a unique amorphous structure, and therefore presents high tensile strength, high elastic limit, low elastic modulus, as well as improved wear and corrosion resistance. For this reason, Zr-based BMG is emerging as a promising material for applications in the aviation, automotive, and healthcare industries. However, Zr-based BMG is classed as an extremely difficult-to-cut material. At very low cutting speeds, lamellar chips are formed accompanied by high frequency fluctuations. At higher cutting speeds, dazzling light is emitted during BMG chip formation and severe oxidation, crystallization, and melting of the working material occur, and consequently, causing premature failure of the tool, loss of amorphous properties, and poor machining accuracy. The purpose of this paper is to investigate chip formation of Zr-based BMG. Based on a survey of existing works, lamellar chip morphology and its underlying mechanism are reviewed and compared with crystalline metals. The key factor affecting light emission during chip formation is uncovered. Further, the influence of oxidation, crystallization, and melting on chip formation is investigated. (C) 2018 The Authors. Published by Elsevier Ltd.