• Advances in materials Research
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• v.3 no.1
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• pp.283-295
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• 2014

In this paper, the microstructure, hardness, tensile deformation and fracture behavior of high strength alloy steel X2M is presented anddiscussed. The influence of both composition and processing on microstructure of the as-provided material and resultant influence of microstructure, as a function of orientation, on hardness, tensile properties and final fracture behavior is highlighted. The macroscopic mode and intrinsic microscopic features that result from fracture of the steel specimens machined from the two orientations, longitudinal and transverse is discussed. The intrinsic microscopic mechanisms governing quasi-static deformation and final fracture behavior of this high strength steel are outlined in light of the effects oftest specimen orientation, intrinsic microstructural effects and nature of loading.

• Elastomers and Composites
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• v.57 no.4
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• pp.188-196
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• 2022

Styrene-butadiene rubber(SBR) is a copolymer of styrene and butadiene. It is composed of 1,2-unit, 1,4-unit, and styrene, and its properties are dependent on its microstructure. In general, rubber composites contain a single rubber or a blended rubber. Similarly, SBR is used by mixing with natural rubber(NR) and butadiene rubber(BR). The composition of a rubber article affects its physical and chemical properties. Herein, an analytical method for determining the microstructure of SBR using via pyrolysis is introduced. Pyrolysis-gas chromatography/mass spectrometry is widely used to analyze the microstructure of polymeric materials. The microstructure of SBR can be determined by analyzing the principal pyrolysis products formed from SBR, such as 4-vinylcyclohexene, styrene, 2-phenylpropene, 3-phenylcyclopentene, and 4-phenylcyclohexene. An analytical method for determining the composition of SBR/NR, SBR/BR, and SBR/NR/BR blends via pyrolysis is introduced. The composition of blended rubber can be determined by analyzing the principal pyrolysis products formed from each rubber component.

• Korean Journal of Materials Research
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• v.21 no.1
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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.

• Korean Journal of Materials Research
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• v.27 no.9
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• pp.477-483
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• 2017

This present study deals with the microstructure and tensile properties of 600 MPa-grade high strength and seismic resistant reinforcing steels. The high strength reinforcing steel (SD 600) was fabricated by Tempcore processing, while the seismic resistant reinforcing steel (SD 600S) was air-cooled after hot-rolling treatment. The microstructure analysis results showed that the SD 600 steel specimen consisted of a tempered martensite and ferrite-pearlite structure after Tempcore processing, while the SD 600S steel specimen had a fully ferrite-pearlite structure. The room-temperature tensile test results indicate that, because of the enhanced solid solution and precipitation strengthening caused by relatively higher contents of C, Mn, Si and V in the SD 600S steel specimen, this specimen, with fully ferrite-pearlite structure, had yield and tensile strengths higher than those of the SD 600 specimen. On the other hand, the hardness of the SD 600 and SD 600S steel specimens changed in different ways according to location, dependent on the microstructure, ferrite grain size, and volume fraction.

• Korean Journal of Materials Research
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• v.28 no.2
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• pp.113-117
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• 2018

Effects of annealing temperature on the microstructure and mechanical properties through thickness of a cold-rolled Cu-3.0Ni-0.7Si alloy were investigated in detail. The copper alloy with thickness of 3 mm was rolled to 50 % reduction at ambient temperature without lubricant and subsequently annealed for 0.5h at $200{\sim}900^{\circ}C$. The microstructure of the copper alloy after annealing was different in thickness direction depending on an amount of the shear and compressive strain introduced by rolling; the recrystallization occurred first in surface regions shear-deformed largely. The hardness distribution of the specimens annealed at $500{\sim}700^{\circ}C$ was not uniform in thickness direction due to partial recrystallization. This ununiformity of hardness corresponded well with an amount of shear strain in thickness direction. The average hardness and ultimate tensile strength showed the maximum values of 250Hv and 450MPa in specimen annealed at $400^{\circ}C$, respectively. It is considered that the complex mode of strain introduced by rolling effected directly on the microstructure and the mechanical properties of the annealed specimens.

• Korean Journal of Materials Research
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• v.22 no.11
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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.

• Journal of the Korean Society for Heat Treatment
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• v.32 no.2
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• pp.68-73
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• 2019

${\alpha}$-titanium alloy has a relatively low heat treatment characteristic and it is mainly subjected to heat treatment for residual stress, recovery or dynamic recrystallization. In this study, commercially pure titanium hollow castings was fabricated by gravity casting. Heat treatments were carried out at $750^{\circ}C$, $850^{\circ}C$ and $950^{\circ}C$ to investigate the effect of post-heat treatment on microstructure and mechanical properties. Beta-transus temperature ($T_{\beta}$) was about $913^{\circ}C$, and equiaxed microstructure was shown at temperature below $T_{\beta}$ and lath-type microstructure at temperature above $T_{\beta}$. Microstructure and mechanical properties did not show any significant difference in the direction of solidification for titanium hollow billet, so it can be seen that it was a well-made material for extrusion process. The optimum heat treatment condition of hollow billet castings for the seamless tube production was $850^{\circ}C$, 4 hr, FC, indicating a combination of equiaxed microstructure and appropriate mechanical properties.

• Transactions of Materials Processing
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• v.30 no.2
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• pp.91-98
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• 2021

The present study deals with the microstructure and mechanical properties of 700 MPa-grade high-strength seismic resistant reinforced steel bars fabricated by various TempCore process conditions. For the steel bars, in the surface region tempered martensite was formed by water cooling and subsequent self-tempering during TempCore process, while in the center region there was ferrite-pearlite or bainite microstructure. The steel bar fabricated by the highest water flow and the lowest equalizing temperature had the highest hardness in all regions due to the relatively fine microstructure of tempered martensite and bainite. In addition, the steel bar having finer microstructures as well as the high fraction of tempered martensite in the surface region showed the highest yield and tensile strengths. The presence of vanadium precipitates and the high fraction of ferrite contributed to the improvement of seismic resistance such as high tensile-to-yield strength ratio and high uniform elongation.

• Journal of the Korean Society for Heat Treatment
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• v.3 no.1
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• pp.25-33
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• 1990

Recently developed austempered ductile irons(A.D.I.) have good mechanical properties. However it is still needed to examine the relationships between microstructures related to banitic reaction and the mechanical properties. From the mechanical tests such as impact test, hardness test, tensile test, and the microstructure observations, we concluded that the good mechanical properties of A.D.I. came from the fine banitic ferrite structure formed during the first stage of the austempering reaction.

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.22-22
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• 2002

It is well known that nanoscale magnetic materials can exhibit significantly different magnetic properties than the corresponding bulk materials. In present work, we summarized the preparation, microstructure, Mossbauer study and magnetic properties of nanocomposites. It was found that both grain size and the amount of magnetically soft phase ${\alpha}$-Fe play a very important role in determining the magnetic properties. (omitted)