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research-article

Microhardness prediction based on a microstructure-sensitive flow stress model during high speed machining Ti-6Al-4V

[+] Author and Article Information
Qingqing Wang

Key Laboratory of High Efficiency and Clean Mechanical Manufacture of MOE, School of Mechanical Engineering, Shandong University, Jinan 250061, P. R. ChinaKey National Demonstration Center for Experimental Mechanical Engineering Education, Shandong University, Jinan 250061, P. R. China
sduwangqingqing@gmail.com

Zhanqiang Liu

Key Laboratory of High Efficiency and Clean Mechanical Manufacture of MOE, School of Mechanical Engineering, Shandong University, Jinan 250061, P. R. ChinaKey National Demonstration Center for Experimental Mechanical Engineering Education, Shandong University, Jinan 250061, P. R. China
melius@sdu.edu.cn

1Corresponding author.

ASME doi:10.1115/1.4039889 History: Received December 18, 2017; Revised March 24, 2018

Abstract

Exploring the hardening mechanisms during high speed machining (HSM) is an effective approach to improve the fatigue strength and the wear resistance of machined surface and to control the fragmentation of chips in a certain range of hardness. In this paper, the microhardness variation is explored from the perspective of microstructural evolutions, as a direct consequence of the severe deformation during HSM Ti-6Al-4V alloy. A microstructure-sensitive flow stress model coupled the phenomena of grain refinement, deformation twinning and phase transformations is firstly proposed. Then the microstructure-sensitive flow stress model is implemented into the cutting simulation model via a user defined subroutine to analyze the flow stress variation induced by the microstructure evolutions during HSM Ti-6Al-4V. Finally, the relationship between the microhardness and flow stress is developed and modified based on the classical theory that the hardness is directly proportional to the flow stress. The study shows that the deformation twinning (generated at higher cutting speeds) plays a more important role in the hardening of Ti-6Al-4V compared with the grain refinement and phase transformation. The predicted microhardness distributions align well with the measured values. It provides a novel thinking that it is plausible to obtain a high microhardness material via controlling the microstructure alterations during machining process.

Copyright (c) 2018 by ASME
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