• Title, Summary, Keyword: microstructure

Search Result 7,392, Processing Time 0.046 seconds

The Changes of Microstructure, Morphology, and Mechanical Properties of Solvent Treated PET POY (Partially Oriented Yarn) (폴리에스테르 부분배향사의 용매처리에 따른 내부구조 및 인장성질의 변화)

  • Shin, Hae Won;Ryu, Hyo Seon
    • Journal of the Korean Society of Clothing and Textiles
    • /
    • v.17 no.1
    • /
    • pp.63-75
    • /
    • 1993
  • Partially oriented polyester yarn (PET POY) was treated in the unrestrained state using various solvents at different temperatures. Interactions between PET POY & solvents were estimated by the changes of microstructure, morphology and mechanical properties. The correlation between the changes of microstructure & morphology and the changes of mechanical properties was also studied. TCE, Dioxane, O-DCB, DMF, and BA were found to be active solvents, while Iso-AA and water were found to be weak solvents. PET POY was affected mainly by the solvents when treated with active solvents and affected mainly by heat when treated with weak solvents. Changes by the solvent treatment in microstructure and morphology were : an increase in crystallinity, a change in birefringence, a shrinkage in length, and a change in DSC curve. As for the changes in mechanical properties, findings in the PET POY when treated with solvents were : a decrease in stress-at-break, a change in yield stress, an increase in strain-at-break & yield strain, and a decrease in initial modulus. Changes in microstructure and morphology directly affected the mechanical properties.

  • PDF

Microstructure, Hardness and Tensile Properties of 600 MPa-Grade High-Strength and Seismic Resistant Reinforcing Steels (600 MPa급 고강도 일반 및 내진 철근의 미세조직, 경도와 인장 특성)

  • Seo, Ha-Neul;Lee, Sang-In;Hwang, Byoungchul
    • Korean Journal of Materials Research
    • /
    • v.27 no.9
    • /
    • pp.477-483
    • /
    • 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.

The Influence of Microstructure on the Bauschinger Effect in X80 Grade API Steel (X80급 API 강의 바우싱거 효과에 미치는 미세조직의 영향)

  • Park, J.S.;Kim, D.W.;Chang, Y.W.
    • Transactions of Materials Processing
    • /
    • v.15 no.2
    • /
    • pp.118-125
    • /
    • 2006
  • API steel is used for line-pipe to transport the oil and natural gas. As the recent trends in the development of API steel are towards the use of larger diameter and thicker plate, many researches have been studied to achieve higher strength, higher toughness and lower yield ratio in API steel. However, the strength of API steel after pipe forming is changed depending on the competition of the Bauschinger effect and work hardening which are affected by the strain history during pipe forming process. So, the purpose of this study is to investigate the influence of microstructure on the Bauschinger effect for API steel. To change the microstructure of API steel we have changed the hot rolling condition and the amounts of V and Cu addition. The compression-tensile test and the microstructure observation by OM and TEM were conducted to investigate the yield strength drop and the correlation between the Bauschinger effect and microstructure of API steel. The experimental results show that the increase of polygonal ferrites volume fraction increases the Baushcinger effect due to the back stress which comes from the increase of mobile dislocation density at polygonal ferrite interior during the compressive deformation. The hot rolling condition was more effective on the Bauschinger effect in API steel than the small amount of V and Cu addition.

Microstructure and Mechanical Properties of Mo-Si-N Coatings Deposited by a Hybrid Coating System (하이브리드 코팅시스템에 의해 제조된 Mo-Si-N 박막의 미세구조 및 기계적 특성연구)

  • Heo, Su-Jeong;Yun, Ji-Hwan;Kang, Myung-Chang;Kim, Kwang-Ho
    • Journal of the Korean institute of surface engineering
    • /
    • v.39 no.3
    • /
    • pp.110-114
    • /
    • 2006
  • In this work, comparative studies on microstructure and mechanical properties between $Mo_2N$ and Mo-Si-N coatings were conducted. Ternary Mo-Si-N coatings were deposited on AISI D2 steel substrates by a hybrid method, where AIP technique was combined with a magnetron sputtering technique. Instrumental analyses of XRD, HRTEM, and XPS revealed that the Mo-Si-N coatings must be a composite consisting of fine $Mo_2N$ crystallites and amorphous $Si_3N_4$. The hardness value of Mo-Si-N coatings significantly increased from 22 GPa of $Mo_2N$ coatings to about 37 GPa with Si content of 10 at.% due to the refinement of $Mo_2N$ crystallites and the composite microstructure characteristics. The average friction coefficient of the Mo-Si-N coatings gradually decreased from 0.65 to 0.4 with increasing Si content up to 15 at.%. The effects of Si content on microstructure and mechanical properties of Mo-N coatings were systematically investigated.

Effect of Cast Microstructure on Fatigue Behaviors of A356 Aluminum Alloy for Automotive Wheel (자동차휠용 A356 알루미늄 합금의 주조조직이 피로특성에 미치는 영향)

  • Song, Jeon-Young;Park, Joong-Cheol;Ahn, Yong-Sik
    • Journal of Korea Foundry Society
    • /
    • v.30 no.1
    • /
    • pp.46-51
    • /
    • 2010
  • Recently, automotive industry is attempting to replace steels for automotive parts with light-weight alloys such as aluminum alloy, because of the growing environmental regulations governing exhaust gas and the engine effectiveness of a vehicle. The low cycle fatigue (LCF) and high cycle fatigue (HCF) properties as well as the microstructure and tensile property were investigated on the low pressure cast A356 aluminum alloy wheel, which was followed by T6 heat treatment. The cast microstructure of the alloy influenced significantly on the low cycle and high cycle fatigue behaviors. The rim part of cast aluminum alloy wheel showed higher low cycle and high cycle fatigue strength compared with the spoke part, which should be caused by higher cooling rate of rim part. The spoke part of the wheel showed coarser dendrite arm spacing (DAS) and wide eutectic zone in the microstructure, which resulted in the partial brittle fracture and lower fatigue life time.

Effect of Si on the Microstructure and Mechanical Properties of Ti-Al-Si-C-N Coatings (Si 함량에 따른 Ti-Al-Si-C-N 코팅막의 미세구조와 기계적 특성의 변화에 관한 연구)

  • Hong, Young-Su;Kwon, Se-Hun;Kim, Kwang-Ho
    • Journal of the Korean institute of surface engineering
    • /
    • v.42 no.2
    • /
    • pp.73-78
    • /
    • 2009
  • Quinary Ti-Al-Si-C-N films were successfully synthesized on SUS 304 substrates and Si wafers by a hybrid coating system combining an arc ion plating technique and a DC reactive magnetron sputtering technique. In this work, the effect of Si content on the microstructure and mechanical properties of Ti-Al-C-N films were systematically investigated. It was revealed that the microstructure of Ti-Al-Si-C-N coatings changed from a columnar to a nano-composite by the Si addition. Due to the nanocomposite microstructure of Ti-Al-Si-C-N coatings, the microhardness of The Ti-Al-Si-C-N coatings significantly increased up to 56 GPa. In addition the average friction coefficients of Ti-Al-Si-C-N coatings were remarkably decreased with Si addition. Therefore, Ti-Al-Si-C-N coatings can be applicable as next-generation hard-coating materials due to their improved hybrid mechanical properties.

Fabrication SiCN micro structures for extreme high temperature systems (초고온 시스템용 SiCN 마이크로 구조물 제작)

  • Thach, Phan Dui;Chung, Gwiy-Sang
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
    • /
    • /
    • pp.216-216
    • /
    • 2009
  • This paper describes a novel processing technique for the fabrication of polymer-derived SiCN (silicone carbonitride) microstructures for extreme microelectromechanical system (MEMS) applications. A polydimethylsiloxane (PDMS) mold was formed on an SU-8 pattern using a standard UV photolithographic process. Next, the liquid precursor, polysilazane, was injected into the PDMS mold to fabricate free-standing SiCN microstructures. Finally, the solid polymer SiCN microstructure was cross-linked using hot isostatic pressure at $400^{\circ}C$ and 205 bar. The optimal pyrolysis and annealing conditions to form a ceramic microstructure capable of withstanding temperatures over $1400^{\circ}C$ were determined. Using the optimal process conditions, the fabricated SiCN ceramic microstructure possessed excellent characteristics includingshear strength (15.2 N), insulation resistance ($2.163{\times}10^{14}\;{\Omega}$, and BDV (1.2 kV, minimum). Since the fabricated ceramic SiCN microstructure has improved electrical and physical characteristics compared to bulk Si wafers, it may be applied to harsh environments and high-power MEMS applications such as heat exchangers and combustion chambers.

  • PDF

Microstructure and Impact Toughness of Weld Metal in Multipass Welded Super Duplex Stainless Steel (다층용접한 슈퍼 듀플렉스 스테인리스강 용접금속의 조직 및 충격인성)

  • Seo, Won-Chan;Park, Chan;Bang, Kook-Soo
    • Journal of Ocean Engineering and Technology
    • /
    • v.26 no.6
    • /
    • pp.27-32
    • /
    • 2012
  • The effects of reheating during welding on the microstructure and impact toughness of weld metal in 25% Cr super duplex stainless steels were investigated. Using different heat inputs, weld metals with different reheated regions were obtained. This showed that, depending on the reheating temperature, the microstructure in the reheated region was quite different from that of the as-deposited microstructure. When reheated into the ${\gamma}+{\alpha}$ temperature range, fine intragranular austenite was formed in the as-deposited columnar structure. However, when reheated above the ${\alpha}$ solvus temperature range, most of the columnar structure disappeared and fine equiaxed austenite and ferrite were formed. Because of the larger amount of fine austenite in the reheated region, a higher impact toughness was obtained in the weld metal with a higher amount of reheated region.

Microstructure and Mechanical Properties of a Copper Alloy Sheet Processed by a Differential Speed Rolling (이속압연에 의해 가공된 동합금 판재의 조직 및 기계적 특성)

  • Lee, Seong-Hee
    • Korean Journal of Materials Research
    • /
    • v.22 no.11
    • /
    • pp.581-586
    • /
    • 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.

Microstructure Evolution of Superalloy Nimonic 80A (초내열합금 Nimonic 80A의 미세조직 변화에 관한 연구)

  • Jeong H. S.;Cho J. R.;Park H. C.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
    • /
    • /
    • pp.174-177
    • /
    • 2004
  • The nickel-based alloy Nimonic 80A possesses strength, and corrosion, creep and oxidation resistance at high temperature. These products are used for aerospace, marine engineering and power generation, etc. The control of forging parameters such as strain, strain rate, temperature and holding time is important because the microstructure change in hot working affects the mechanical properties. It is necessary to understand the microstructure variation evolution. The microstructure change evolution occurs by recovery, recrystallization and grain growth phenomena. The dynamic recrystallization evolution has been studied in the temperature range $950-1250^{\circ}C$ and strain rate range $0.05-5s^{-1}$ using hot compression tests. The metadynamic recrystallization and grain growth evolution has been studied in the temperature range $950-1250^{\circ}C$ and strain rate range 0.05, $5s^{-1}$, holding time range 5, 10, 100, 600 sec using hot compression tests. Modeling equations are developed to represent the flow curve, recrystallized grain size, recrystallized fraction and grain growth phenomena by various tests. Parameters of modeling equation are expressed as a function of the Zener-Hollomon parameter. The modeling equation for grain growth is expressed as a function of initial grain size and holding time.

  • PDF