• 한국재료학회지
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• 제22권11호
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• pp.581-586
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• 2012

The microstructure and mechanical properties of a copper alloy sheet processed by differential speed rolling (DSR) were investigated in detail. A copper alloy with thickness of 3 mm was rolled to a 50% reduction at ambient temperature without lubrication and with a differential speed ratio of 2.0:1. For comparison, conventional rolling (CR), in which the rolling speeds of the upper and lower rolls is 2.0 m/min, was also performed under the same rolling conditions. The shear strain of the sample processed by CR showed positive values at the positions of the upper roll side and negative values at the positions of the lower roll side. On the other hand, the sample processed by the DSR showed zero or positive shear strain values at all positions. However, the microstructure and mechanical properties of the as-rolled copper alloys did not show such significant differences between the CR and the DSR. The samples rolled by the CR and the DSR exhibited a typical deformation structure. In addition, the DSR processed samples showed a typical rolling texture in which {112}<111>, {011}<211> and {123}<634> components were developed at all positions. Therefore, it is concluded that the DSR was very effective for the introduction of a uniform microstructure throughout the thickness of the copper alloy.

• 한국재료학회지
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• 제26권1호
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• pp.8-12
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• 2016

Effects of conventional rolling(CR) and differential speed rolling(DSR) on the microstructure and mechanical properties of Cu-Ni-Si alloy were investigated in detail. The copper alloy with thickness of 3 mm was rolled to 50 % reduction at ambient temperature without lubricant with a differential speed ratio of 2:1. The conventional rolling in which the rolling speed of upper and lower rolls is identical was performed under identical rolling conditions. The shear strain introduced by the CR showed positive values at positions of upper roll side and negative values at positions of lower roll side. However, it showed zero or positive values at all positions for the samples rolled by the DSR. The microstrucure and texture development of the as-rolled copper alloy did not show any significant difference between CR and DSR. The tensile strength of the DSR processed specimen was larger than that of the CR processed specimen. The effects of rolling methods on the microstructure and mechanical properties of the as-rolled copper alloy are discussed in terms of the shear strain.

• 한국재료학회지
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• 제23권7호
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• pp.392-398
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• 2013

A two-pass differential speed rolling(DSR) was applied to a deoxidized low-phosphorous copper alloy sheet in order to form a homogeneous microstructure. Copper alloy with a thickness of 3 mm was rolled to 75 % reduction by two-pass rolling at $150^{\circ}C$ without lubrication at a differential speed ratio of 2.0:1. In order to introduce uniform shear strain into the copper alloy sheet, the second rolling was performed after turning the sample by $180^{\circ}$ on the transverse direction axis. Conventional rolling(CR), in which the rotating speeds of the upper roll and lower roll are identical to each other, was also performed by two-pass rolling under a total rolling reduction of 75 %, for comparison. The shear strain introduced by the conventional rolling showed positive values at positions of the upper roll side and negative values at positions of the lower roll side. However, samples processed by the DSR showed zero or positive values at all positions. {100}//ND texture was primarily developed near the surface and center of thickness for the CR, while {110}//ND texture was primarily developed for the DSR. The difference in misorientation distribution of grain boundary between the upper roll side surface and center regions was very small in the CR, while it was large in the DSR. The grain size was smallest in the upper roll side region for both the CR and the DSR. The hardness showed homogeneous distribution in the thickness direction in both CR and DSR. The average hardness was larger in CR than in DSR.

• 대한금속재료학회지
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• 제48권10호
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• pp.942-950
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• 2010

The microstructure and mechanical properties of a Cu-Fe-P copper alloy processed by differential speed rolling (DSR) were investigated in detail. The copper alloy, with a thickness of 3 mm, was rolled to 50% reduction at ambient temperature without lubrication with a differential speed ratio of 2.0:1 and then annealed for 0.5h at various temperatures ranging from 100 to $800^{\circ}C$. Conventional rolling was performed under the same rolling conditions for comparison. The shear strain introduced by the conventional rolling process showed positive values at the positions of the upper roll side and negative values at the positions of the lower roll side. However, the result was zero or positive values at all positions for samples rolled by DSR. The effects of DSR on the microstructure and mechanical properties of the as-rolled and subsequently annealed samples are discussed.

• 소성∙가공
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• 제30권4호
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• pp.195-200
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• 2021

In this study, we investigated the dominant processing variables that would influence the microstructural development of AA6061 deformed by differential speed rolling (DSR) at ambient temperature. For this purpose, we carried out a series of DSR on the samples to investigate the effects of roll speed ratio, sample rotation, and number of operation under specific rotation. Among these, the condition with a height reduction of 75% at a speed ratio of 1:4 through rotation along rolling direction (RR) displayed the pronounced results of more homogenous matrix-structure and superior mechanical properties than the others tested in this study. This was mainly due to the cross shearing of macro-shear pattern in segment where dynamic recrystallization took place with ease throughout the sample. Thus, an average microhardness value of 101 Hv was obtained in the present sample deformed by 4-pass DSR with RR where macro cross-shearing was effectively applied.

• 한국재료학회지
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• 제21권1호
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• pp.15-20
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• 2011

The effects of conventional rolling (CR) and differential speed rolling (DSR) on the microstructure and mechanical properties of a copper alloy sheet were investigated in detail. A copper alloy with thickness of 3 mm was rolled to a 50% reduction at ambient temperature without lubrication with a differential speed ratio of 2:1; sample was then annealed for 0.5h at various temperatures from 100 to $800^{\circ}C$. Conventional rolling, in which the rolling speed of the upper and lower rolls is identical, was performed under the same rolling conditions. The shear strain introduced by the CR showed positive values at positions on the upper roll side and negative values at positions on the lower roll side. However, the shear strain showed a zero or positive value at all positions for the samples rolled by the DSR. The microstrucure and mechanical properties of the as-rolled copper alloy did not show very significant differences between the CR and DSR for the microstructure and mechanical properties. However, those properties showed very significant differences in the case of the annealed samples. The effects of rolling method on the microstructure and mechanical properties of the as-rolled and subsequently annealed materials are discussed in terms of the shear strain.

• 소성∙가공
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• 제27권1호
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• pp.12-17
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• 2018

This paper outlines the research findings on the microstructure and mechanical properties of AZ31 Mg alloy fabricated by differential speed rolling (DSR) with respect to processing variables such as temperature, roll speed ratio (RSR), and deformation route. The resultant microstructure of the sample, deformed by 2-pass DSRs at 473 K, comprised finer grains with more uniform distribution than those at 573 and 623 K. This was due to active recrystallization, which was expected to appear during DSR at temperatures higher than 573 K. When the sample was deformed via DSR with RSR of 1:4 for the upper and lower rolls at 453 K, the values of yield and ultimate tensile strength were observed to be higher than their counterpart with RSR of 1:1. The application of sample rotation around the longitudinal axis would give rise to an excellent combination of tension strength (~330 MPa) and ductility (~20 %) at ambient temperatures. This is discussed based on its uniform fine grained structure and the softening of basal texture.

• 한국재료학회지
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• 제25권3호
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• pp.149-154
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• 2015

We evaluated the developed microstructures and mechanical properties of a severely plastically deformed Ni-30Cr alloy. Normal rolling and differential speed rolling were used as deformation processes, and the thicknesses of the specimens were reduced to 68 % of the original thickness after holding at $700^{\circ}C$ for 10 min and annealing at $700^{\circ}C$ for 40 min to obtain a fully recrystallized microstructure. Electron backscattering diffraction was used to analyze the characteristic distribution of the grain boundaries on the deformed and annealed specimens. Differential speed rolling was more effective for refining grains in comparison with normal rolling. The grain size was refined from 33 mm in the initial material to 8.1 mm with normal rolling and 5.5 mm with differential speed rolling. The more refined grain in the differential-speed-rolled material directly resulted in increases in the yield and tensile strengths by 68 % and 9.0%, respectively, compared to normal rolling. We systematically explain the relationship between the grain refinement and mechanical properties through a plastically deformed Ni-30Cr alloy based on the development of a deformation texture. The results of our study show that the DSR process is very effective when used to enhance the mechanical properties of a material through grain refinement.

• 대한금속재료학회지
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• 제47권2호
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• pp.121-128
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• 2009

The strain, microstructure and mechanical properties through thickness of an oxygen free copper(OFC) processed by differential speed rolling(DSR) were investigated in detail. The OFC sample with thickness of 1 mm was rolled to 35% reduction at ambient temperature without lubrication changing the differential speed ratio from 1.0:1 to 2.2:1. The shear strain introduced by the conventional rolling showed positive values at positions of upper roll side and negative values at positions of lower roll side. However, it showed zero or positive values at all positions for the samples rolled by the DSR. The effects of strain distribution through thickness of the coper sheets on microstructure, texture and mechanical properties are discussed in the present study.

• 대한금속재료학회지
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• 제48권7호
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• pp.605-614
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• 2010

Conventional rolling (symmetric) and differential speed rolling (DSR) were both applied to AA1050 sheets at various velocity ratios, from 1 to 2 between the top and bottom rolls. An electron backscatter diffraction (EBSD) technique was used to measure texture inhomogeneity through the thickness direction. After the annealing process, the annealing texture of the DSR processed sheets was different from that of conventionally rolled sheets. The velocity ratio between the top and bottom rolls affected the texture inhomogeneity and macroscopic plastic strain ratio of the AA1050 sheets. A prediction for the macroscopic plastic strain ratio of AA1050 sheets was carried out using a visco-plastic self-consistent (VPSC) polycrystal model. The strain ratio directionality that was predicted using the VPSC polycrystal model was in good agreement with experimental results.