Study of Machining-Induced Microstructure Variations of ECAE-Processed Ultrafine-Grained Copper

2009 ◽  
Author(s):  
Yong Huang ◽  
Mason Morehead
Keyword(s):  
Equal Channel Angular Extrusion ◽  
High Strength ◽  
Outer Radius ◽  
Precision Machining ◽  
Grain Sizes ◽  
Microstructure Stability ◽  
Ultrafine Grained ◽  
Structural Applications ◽  
Ultrafine Grained Materials ◽  
Stability Issues

Various methods for production of bulk ultrafine-grained (UFG)/nanostructured materials have been developed. Recently, a top-down approach named equal channel angular extrusion (ECAE), a form of severe plastic deformation (SPD), has gained increasing attention in making bulk UFG materials. Such bulk materials are favored for their high strength, wear resistance, ductility, and high strain-rate superplasticity, which makes them suitable for light weight engineering and medical applications. Further precision machining work is normally indispensable for structural applications after bulk ultrafine grained materials are manufactured from any SPD processes. Unfortunately, the microstructure stability issues in precision machining such materials are frequently ignored. Using an ECAE copper bar as an example, this study has investigated its machining-induced workpiece microstructure variation. It has been found that there was a small increase in the size parameter median and the average arithmetic and area weighted grain sizes when comparing those of machined and unmachined bars, and the measured grain sizes oscillated slightly in the radial direction of the machined bar. Dislocation density was shown to have the most reduction at the outer radius location of the machined ECAE bar where more heat and/or higher pressure were experienced.

Machinability Research and Workpiece Microstructure Characterization in Turning of Ultrafine Grained Copper

2005 ◽  
Author(s):  
Mason Morehead ◽  
Yong Huang
Keyword(s):  
Nanostructured Materials ◽  
Equal Channel Angular Extrusion ◽  
High Strength ◽  
Precision Machining ◽  
Top Down ◽  
Microstructure Stability ◽  
Ultrafine Grained ◽  
Structural Applications ◽  
Stability Issues ◽  
Tool Cutting

Various methods for production of bulk ultrafine grained/nanostructured materials have been developed. They can be classified into two categories based on their approaches: the bottom-up and top-down approaches. Recently, a top-down approach named equal channel angular extrusion (ECAE), a form of severe plastic deformation (SPD), has been gaining more and more attention in making bulk ultrafine grained/nanostructured materials. Such bulk materials are favored for there high strength, wear resistance, ductility, and high strain-rate superplasticity, which makes them suitable for light weight engineering and medical applications. Further precision machining work is normally indispensable for structural applications after bulk ultrafine grained/nanostructured materials are manufactured from any SPD processes. While researchers are increasingly interested in commercially producing SPD-processed bulk ultrafine grained/nanostructured materials and characterizing their chemical and physical properties, the machinability and microstructure stability issues in precision machining such materials are frequently ignored. Using an ECAE processed bulk ultrafine grained copper bar as an example, this study investigates the machinability as well as machining-induced workpiece microstructure variation of such ECAE processed materials in precision turning. Tool cutting performance in turning the ultrafine grained copper bar is also compared with that of the regular copper bar.

Study of Machining-Induced Microstructure Variations of Nanostructured/Ultrafine-Grained Copper Using XRD

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Yong Huang ◽  
Mason Morehead
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Dislocation Density ◽  
Equal Channel Angular Extrusion ◽  
Outer Radius ◽  
X Ray Diffraction ◽  
X Ray ◽  
Grain Sizes ◽  
Ultrafine Grained ◽  
Area And Volume

Various methods for the production of bulk nanostructured (NS)/ultrafine-grained (UFG) materials have been developed, including equal channel angular extrusion (ECAE), a form of severe plastic deformation. Using an ECAE NS/UFG copper bar as an example, this study has investigated machining-induced workpiece microstructure variation using X-ray diffraction. It has been found that (1) under gentle cutting conditions, there was a 10% increase in the median grain size compared with unmachined ECAE NS/UFG copper bars. Increases in the arithmetic-, area-, and volume-weighted grain sizes were found to be 10%, 8%, and 8%, respectively, and (2) an average 27% drop in the dislocation density was observed between the machined and unmachined ECAE copper bars. The dislocation density was shown to have the most reduction (−39%) at the outer radius of the machined ECAE bar where more heat and/or higher pressure were experienced.

The Processing of Ultrafine-Grained Materials Using High-Pressure Torsion

2007 ◽  
Vol 558-559 ◽  
pp. 1283-1294 ◽  
Author(s):  
Cheng Xu ◽  
Z. Horita ◽  
Terence G. Langdon
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
High Pressure ◽  
High Pressure Torsion ◽  
Metallic Materials ◽  
Grain Sizes ◽  
Ultrafine Grained ◽  
Wide Range ◽  
Ultrafine Grained Materials ◽  
Thin Disks

It is now well-established that processing through the application of severe plastic deformation (SPD) leads to a significant reduction in the grain size of a wide range of metallic materials. This paper examines the fabrication of ultrafine-grained materials using high-pressure torsion (HPT) where this process is attractive because it leads to exceptional grain refinement with grain sizes that often lie in the nanometer or submicrometer ranges. Two aspects of HPT are examined. First, processing by HPT is usually confined to samples in the form of very thin disks but recent experiments demonstrate the potential for extending HPT also to bulk samples. Second, since the strains imposed in HPT vary with the distance from the center of the disk, it is important to examine the development of inhomogeneities in disk samples processed by HPT.

scholarly journals Superplasticity in Ultrafine-Grained Materials.

2018 ◽  
Vol 54 (1) ◽  
pp. 46-55 ◽  
Author(s):  
Megumi Kawasaki ◽  
Terence G. Langdon
Keyword(s):  
Visual Display ◽  
Superplastic Flow ◽  
Small Samples ◽  
Flow Properties ◽  
Flow Process ◽  
Grain Sizes ◽  
Ultrafine Grained ◽  
High Elongation ◽  
Ultrafine Grained Materials ◽  
Basic Characteristics

Abstract Superplasticity refers to the ability of a polycrystalline solid to exhibit a high elongation, of at least 400% or more, when testing in tension. The basic characteristics of superplastic flow are now understood and a theoretical model is available to describe the flow process both in conventional superplastic materials where the grain sizes are a few micrometers and in ultrafinegrained materials processed by severe plastic deformation where the grain sizes are in the submicrometer range. This report describes the basic characteristics of superplastic metals, gives examples of flow in ultrafine-grained materials, demonstrates the use of deformation mechanism mapping for providing a visual display of the flow processes and provides a direct comparison with the conventional model for superplastic flow. The report also describes the potential for using nanoindentation to obtain detailed information on the flow properties using only exceptionally small samples.

Analysis of Deformation Textures and Microstructure in ECAE Processed Copper Single Crystals via Route C

2007 ◽  
Vol 561-565 ◽  
pp. 929-932
Author(s):  
Gang Wang ◽  
Shi Ding Wu ◽  
Yan Dong Wang ◽  
Ya Ping Zong ◽  
Claude Esling ◽  
...  
Keyword(s):  
Single Crystals ◽  
Equal Channel Angular Extrusion ◽  
Texture Evolution ◽  
Effective Means ◽  
Pure Copper ◽  
Ultrafine Grained ◽  
Deformation Textures ◽  
Ultrafine Grained Materials ◽  
Copper Single Crystals ◽  
Mechanisms Of Plastic Deformation

Equal channel angular extrusion (ECAE) is an effective means of producing ultrafine-grained materials with extraordinary mechanical properties. Texture evolution and microstructure in pure copper single crystals processed by ECAE for up to five passes via route C are investigated to understand mechanisms of plastic deformation and grain refinement during ECAE. The experimental textures after the third pass ECAE process recovers that after one pass ECAE process. The main textures approaches a stable one after four passes of ECAE process via Route C while the intensity of main texture components decreases gradually. Local TEM-OIM measurements shows that grain subdivision in ECAE-processed samples occurs with the formation of many low angle grain boundaries.

High ductility of ultrafine-grained steel via phase transformation

2008 ◽  
Vol 23 (6) ◽  
pp. 1578-1586 ◽  
Author(s):  
S. Cheng ◽  
H. Choo ◽  
Y.H. Zhao ◽  
X-L. Wang ◽  
Y.T. Zhu ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Tensile Ductility ◽  
High Strength ◽  
Strain Rate Effect ◽  
Inhomogeneous Deformation ◽  
Ultrafine Grained ◽  
Structural Applications ◽  
Order Of Magnitude ◽  
Strength And Ductility ◽  
Ultrafine Grained Steel

There is often a tradeoff between strength and ductility, and the low ductility of ultrafine-grained (UFG) materials has been a major obstacle to their practical structural applications despite their high strength. In this study, we have achieved a ∼40% tensile ductility while increasing the yield strength of FeCrNiMn steel by an order of magnitude via grain refinement and deformation-induced martensitic phase transformation. The strain-rate effect on the inhomogeneous deformation behavior and phase transformation was studied in detail.

The Flow Behavior of Ultrafine-Grained Materials

2014 ◽  
Vol 1013 ◽  
pp. 7-14
Author(s):  
Terence G. Langdon
Keyword(s):  
Plastic Deformation ◽  
High Pressure Torsion ◽  
Flow Behavior ◽  
Flow Characteristics ◽  
High Strength ◽  
Flow Properties ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Small Grains ◽  
Ultrafine Grained Materials

Processing through the application of severe plastic deformation (SPD) leads to very significant grain refinement with grains that are typically in the submicrometer or even the nanometer range. These ultrafine-grained (UFG) materials provide an opportunity for achieving exceptional flow properties including high strength at ambient temperature and, if the very small grains are reasonably stable, superplastic elongations at high testing temperatures. These flow characteristics are examined for materials processed using the two SPD procedures of equal-channel angular pressing (ECAP) and high-pressure torsion (HPT).

Effects of Inner Corner Angle on Strain Distribution of ECAPed Aluminum Alloy

2013 ◽  
Vol 743 ◽  
pp. 231-234
Author(s):  
Xi Liang Chen ◽  
Qing Nan Shi
Keyword(s):  
Strain Distribution ◽  
Deformation Process ◽  
Effective Strain ◽  
High Strength ◽  
Deformation Method ◽  
Corner Angle ◽  
Angular Pressing ◽  
Ecap Process ◽  
Ultrafine Grained ◽  
Ultrafine Grained Materials

Ultrafine-grained materials have excellent mechanical properties, which include the high strength and toughness. Equal channel angular pressing (ECAP) is one kind of severe plastic deformation method to make ultrafine-grained metals. The ECAP processes are simulated by finite element method (FEM) in this work. The effects of inner corner angle on strain distribution during the deformation process are numerically analyzed. The evolutions of effective strain on three points of different deformation are compared. The results show that the deformation becomes severe on each point when the inner corner angle is less than 90o, which is different from the situation when the inner corner angle is equal to or greater than 90o. The results are useful for improving the ECAP process to make the structure of metals homogenous.

Dislocation and Diffusion Deformation Mechanisms of Ultrafine Grained Materials

2009 ◽  
Vol 633-634 ◽  
pp. 121-128 ◽  
Author(s):  
Eduard Kozlov ◽  
Nina Koneva ◽  
N.A. Popova
Keyword(s):  
Grain Size ◽  
Deformation Mechanisms ◽  
Grain Sizes ◽  
Ultrafine Grained ◽  
Diffusion Mechanisms ◽  
Ultrafine Grained Materials ◽  
And Diffusion

Deformation mechanisms of polycrystals as a function of the grain size in the 1nm…1cm interval are studied in this paper. The critical grain sizes are identified. Activity of dislocation and diffusion mechanisms is analyzed. The distribution of deformation in grains with different sizes within the same polycrystal is considered.

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