Effects of Machining Velocity on Ultra-Fine Grained Al 7075 Alloy Produced by Cryogenic Temperature Large Strain Extrusion Machining

In this study, cryogenic temperature large strain extrusion machining (CT-LSEM) as a novel severe plastic deformation (SPD) method for producing ultra-fine grained (UFG) microstructure is investigated. Solution treated Al 7075 alloy was subjected to CT-LSEM, room temperature (RT) LSEM, as well as CT...

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Main Authors: Xiaolong Yin, Haitao Chen, Wenjun Deng
Format: Article
Language:English
Published: MDPI AG 2019-05-01
Series:Materials
Subjects:
Online Access:https://www.mdpi.com/1996-1944/12/10/1656
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spelling doaj-8f61be4af8cb42b4a73d7b7bc749b06f2020-11-25T01:38:42ZengMDPI AGMaterials1996-19442019-05-011210165610.3390/ma12101656ma12101656Effects of Machining Velocity on Ultra-Fine Grained Al 7075 Alloy Produced by Cryogenic Temperature Large Strain Extrusion MachiningXiaolong Yin0Haitao Chen1Wenjun Deng2School of Mechanical and Automotive Engineering, South China University of Technology, No. 381 Wushan Road, Tianhe District, Guangzhou 510641, ChinaSchool of Mechanical and Automotive Engineering, South China University of Technology, No. 381 Wushan Road, Tianhe District, Guangzhou 510641, ChinaSchool of Mechanical and Automotive Engineering, South China University of Technology, No. 381 Wushan Road, Tianhe District, Guangzhou 510641, ChinaIn this study, cryogenic temperature large strain extrusion machining (CT-LSEM) as a novel severe plastic deformation (SPD) method for producing ultra-fine grained (UFG) microstructure is investigated. Solution treated Al 7075 alloy was subjected to CT-LSEM, room temperature (RT) LSEM, as well as CT free machining (CT-FM) with different machining velocities to study their comparative effects. The microstructure evolution and mechanical properties were characterized by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Vickers hardness measurements. It is observed that the hardness of the sample has increased from 105 HV to 169 HV and the chip can be fully extruded under CT-LSEM at the velocity of 5.4 m/min. The chip thickness and hardness decrease with velocity except for RT-LSEM at the machining velocity of 21.6 m/min, under which the precipitation hardening exceeds the softening effect. The constraining tool and processing temperature play a significant role in chip morphology. DSC analysis suggests that the LSEM process can accelerate the aging kinetics of the alloy. A higher dislocation density, which is due to the suppression of dynamic recovery, contributes to the CT-LSEM samples, resulting in greater hardness than the RT-LSEM samples.https://www.mdpi.com/1996-1944/12/10/1656Al 7075 alloycryogeniclarge strain extrusion machiningmicrostructuremicro-hardness
collection DOAJ
language English
format Article
sources DOAJ
author Xiaolong Yin
Haitao Chen
Wenjun Deng
spellingShingle Xiaolong Yin
Haitao Chen
Wenjun Deng
Effects of Machining Velocity on Ultra-Fine Grained Al 7075 Alloy Produced by Cryogenic Temperature Large Strain Extrusion Machining
Materials
Al 7075 alloy
cryogenic
large strain extrusion machining
microstructure
micro-hardness
author_facet Xiaolong Yin
Haitao Chen
Wenjun Deng
author_sort Xiaolong Yin
title Effects of Machining Velocity on Ultra-Fine Grained Al 7075 Alloy Produced by Cryogenic Temperature Large Strain Extrusion Machining
title_short Effects of Machining Velocity on Ultra-Fine Grained Al 7075 Alloy Produced by Cryogenic Temperature Large Strain Extrusion Machining
title_full Effects of Machining Velocity on Ultra-Fine Grained Al 7075 Alloy Produced by Cryogenic Temperature Large Strain Extrusion Machining
title_fullStr Effects of Machining Velocity on Ultra-Fine Grained Al 7075 Alloy Produced by Cryogenic Temperature Large Strain Extrusion Machining
title_full_unstemmed Effects of Machining Velocity on Ultra-Fine Grained Al 7075 Alloy Produced by Cryogenic Temperature Large Strain Extrusion Machining
title_sort effects of machining velocity on ultra-fine grained al 7075 alloy produced by cryogenic temperature large strain extrusion machining
publisher MDPI AG
series Materials
issn 1996-1944
publishDate 2019-05-01
description In this study, cryogenic temperature large strain extrusion machining (CT-LSEM) as a novel severe plastic deformation (SPD) method for producing ultra-fine grained (UFG) microstructure is investigated. Solution treated Al 7075 alloy was subjected to CT-LSEM, room temperature (RT) LSEM, as well as CT free machining (CT-FM) with different machining velocities to study their comparative effects. The microstructure evolution and mechanical properties were characterized by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Vickers hardness measurements. It is observed that the hardness of the sample has increased from 105 HV to 169 HV and the chip can be fully extruded under CT-LSEM at the velocity of 5.4 m/min. The chip thickness and hardness decrease with velocity except for RT-LSEM at the machining velocity of 21.6 m/min, under which the precipitation hardening exceeds the softening effect. The constraining tool and processing temperature play a significant role in chip morphology. DSC analysis suggests that the LSEM process can accelerate the aging kinetics of the alloy. A higher dislocation density, which is due to the suppression of dynamic recovery, contributes to the CT-LSEM samples, resulting in greater hardness than the RT-LSEM samples.
topic Al 7075 alloy
cryogenic
large strain extrusion machining
microstructure
micro-hardness
url https://www.mdpi.com/1996-1944/12/10/1656
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AT wenjundeng effectsofmachiningvelocityonultrafinegrainedal7075alloyproducedbycryogenictemperaturelargestrainextrusionmachining
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