Title

Chip Morphology And Chip Formation Mechanisms During Machining Of Ecae-Processed Titanium

Keywords

chip formation; chip morphology; equal channel angular extrusion; machining; titanium

Abstract

Severe plastic deformation (SPD) processing such as equal channel angular extrusion (ECAE) has been pioneered to produce ultrafine grained (UFG) metals for improved mechanical and physical properties. However, understanding the machining of SPD-processed metals is still limited. This study aims to investigate the differences in chip morphology when machining ECAE-processed UFG and coarse-grained (CG) titanium (Ti) and understand the chip formation mechanism using metallographic analysis, digital imaging correlation (DIC), and nano-indentation. The chip morphology is classified as aperiodic saw-tooth, continuous, or periodic saw-tooth, and changes with the cutting speed. The chip formation mechanism of the ECAE-processed Ti transitions from cyclic shear localization within the low cutting speed regime (such as 0.1 m/s or higher) to uniform shear localization within the moderately high cutting speed regime (such as from 0.5 to 1.0 m/s) and to cyclic shear localization (1.0 m/s). The shear band spacing increases with the cutting speed and is always lower than that of the CG counterpart. If the shear strain rate distribution contains a shift in the chip flow direction, the chip morphology appears saw-tooth, and cyclic shear localization is the chip formation mechanism. If no such shift occurs, the chip formation is considered continuous, and uniform shear localization is the chip formation mechanism. Hardness measurements show that cyclic shear localization is the chip formation mechanism when localized hardness peaks occur, whereas uniform shear localization is operative when the hardness is relatively constant.

Publication Date

3-1-2018

Publication Title

Journal of Manufacturing Science and Engineering, Transactions of the ASME

Volume

140

Issue

3

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1115/1.4038442

Socpus ID

85039939546 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/85039939546

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