Precision-improving manufacturing produces ordered ultra-fine grained surface layer of tungsten heavy alloy through ultrasonic elliptical vibration cutting

• Published in: Materials & design Vol. 220; p. 110859
• Main Authors: Bai, Jinxuan, Xu, Zhiwei, Qian, Linmao
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-08-2022; Elsevier
• Subjects: Brittle-to ductile transition; Nanometer-level surface precision; Tungsten heavy alloys; Ultra-fine grained surface layer; Ultrasonic elliptical vibration cutting; Brittle-to ductile transition; Ultrasonic elliptical vibration cutting; Nanometer-level surface precision; Ultra-fine grained surface layer; Tungsten heavy alloys
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2022.110859

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•Coordinative surface generation between geometry accuracy and microstructure characteristics is investigated in ultra-precision cutting tungsten-based alloy.•A nano-meter level roughness and continuous ultra-fine grained surface is obtained in ductile-mode removal process.•Dislocations accumulation induced by high-strain rate tool impact provides the primary driving forces for brittle-ductile transition and grain recrystallization.
High-precision and ultra-fine grained surface of tungsten heavy alloy exhibits superior service performance that is useful for many applications and shows promises for use as key parts in nuclear protection and precision instruments. The present study concentrated on a kind of precision-improving ultrasonic elliptic vibration cutting approaches, which fabricated nanometer-level surface roughness, inhibited subsurface damages evolution, and formed continuous ultra-fine grained layer microstructure. The surface morphologies have been characterized by ultra-depth three dimensional microscope and white light interferometer. Excellent machined surface quality was achieved under ultrasonic elliptic vibration cutting condition, and an ideal surface roughness of Sa = 70.7 nm was obtained. Microstructural alteration studied using EBSD technique and TEM observation confirmed the generation of ultra-fine grained structure. Surface grain size has been reduced from 50 ∼ 100 μm to 50 ∼ 300 nm without cracks and other micro-damages. Research demonstrated that surface energy accumulation and dislocations clustering induced by high-strain rate diamond tool impact provided the primary driving force of ductile-mode removal and grain recrystallization. A dislocation density-based simulation model was carried out to complement the static experimental investigations. The present work on surface formation and microstructural evolution identified that ultrasonic elliptical vibration machining has potential to deliver improved tungsten-based alloys service performance.