On the effect of grain structure in micro-cutting of polycrystalline aluminate magnesium spinel (PAMS) crystals. (September 2019)

• Record Type: Journal Article
• Authors: Shi, Zhuoqi; Zhao, Qingliang; Wang, Hao; Chen, Junyun; Jin, Tianye; Ji, Tianyu
• Is Part Of: International journal of mechanical sciences. Volume 160(2019)
• Page Start: 372
• Page End: 385
• Publication Date: 2019-09
• Subjects: Anisotropic grain effect -- Polycrystalline aluminate magnesium spinel -- Crack patterns -- Micro cutting test -- Ductile regime machining -- Finite element method; Mechanical engineering -- Periodicals; Génie mécanique -- Périodiques; Mechanical engineering; Maschinenbau; Mechanik; Zeitschrift; Periodicals; 621.05
• DOI: 10.1016/j.ijmecsci.2019.07.003
• Languages: English
• ISSNs: 0020-7403

Abstract

Highlights: Ductile–brittle transition of spinel occurs with a cutting depth from 80 to 163 nm. Crack distribution owes to material anisotropy of randomly oriented grains. Crack-free surface can be achieved with a cutting depth in tens of nanometers. Ploughing effect dominates the cutting process with a cutting depth below 100 nm. Subsurface damage and fractures are evoked ahead of material removal process. Abstract: This paper studies the anisotropic effect induced by the grain structure of polycrystalline aluminate magnesium spinel (PAMS) on the mechanism of surface generation in the micro-cutting process. The critical depth of cut for ductile–brittle transition (DBT) of PAMS is estimated from 81 to 163 nm by plunge-cutting tests. In the cutting tests with constant cutting depths from 250 nm to 1.5 µm, an apparent regional distribution of crack features is clearly observed and it implies that the randomly oriented crystal grains with different slip systems play an important role in brittle-regime surface generation and fractures evolution. An effective way to obtain a ductile-regime machined surface is to decrease the cutting depth to 50 nm, and a flawless surface can be obtained when the cutting depth is as shallow as 30 nm. With such a low cutting depth, the material is mainly removed by the ploughing effect. Finite element method (FEM) model has been developed to simulate the cutting process crossing a grain boundary of two adjacent grains with different anisotropy material properties. The simulation result supports that the subsurface damage and boundary fractures can be evoked ahead of the actual material removal process by the cutting stress propagating from the precedingly machined grain. Different crack-patterns are shown on the finished surfaces of the two adjacent grains of different orientations.