• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2005.10a
• /
• pp.332-335
• /
• 2005

A model is developed to quantitatively analyze the dilatometry curve of carbon steel for the evaluation of phase fraction during transformation. The effect of anisotropic volume change due to transformation mismatch plasticity as well as carbon enrichment in austenite during the transformation is considered in the developed model. The developed model is applied for the analysis of dilatometry curves of carbon steels. The result shows that considering the anisotropic dilatation is very essential to quantitatively evaluate the phase fraction from the dilatation curve.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09a
• /
• pp.260-261
• /
• 2006

The behaviour of steel powder compacts during sintering has been investigated by dilatometry and X-ray computed microtomography. Dilatometry measurements showed that the anisotropic deformation results from various phenomena arising at different moments of the cycle including the delubrication stage. Microtomography provided 3D images of the microstructure induced by prior die pressing and its changes throughout sintering. Finally a schematic description of the main phenomena responsible for the deformation of metal powder compacts during sintering is proposed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2008.05a
• /
• pp.224-224
• /
• 2008

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2007.05a
• /
• pp.107-110
• /
• 2007

It has been reported that the permanent strain could happen during recrystallization and grain growth even under the externally applied stress which is much lower than yield stress. In this study, we performed dilatometry experiments under the various compressive stresses and measured the amount of recrystallization and grain growth induced permanent strain. A new constitutive equation based on the concept of boundary migration induced plasticity was suggested to describe the recrystallization and grain growth induced plasticity. This equation was verified by comparing the calculated values with dilatometric experimental data under the various compressive stresses.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09a
• /
• pp.568-569
• /
• 2006

The use of the nickel free, high nitrogen stainless steel powder and nitriding during sintering of iron based materials have been shown as an alternative way to the conventional PM stainless steels containing nickel. Nitrogen as an alloying element for iron improves in an effective way the properties of sintered alloyed steels. The powder metallurgy route is a suitable way to introduce nitrogen into these alloys and, in particular, to produce high nitrogen (close to the solubility limit) stainless steels. The paper presents and discusses the nitriding behavior of nickel-free stainless steels produced by powder metallurgy method. Alloyed melt was atomized by nitrogen and in this way nitrogen was introduced into the powder. Further nitriding occurred during sintering in a nitrogen atmosphere. For comparison, compacts having the same composition as an alloyed powder were produced from elemental powders mixture. Sintering-nitriding behaviour of investigated materials has been controlled by dilatometry, chemical and X-Ray phase analysis and metallography. Mechanical properties of sintered compacts were also measured.

• Journal of Industrial and Engineering Chemistry
• /
• v.67
• /
• pp.1-11
• /
• 2018

Polymer composites offered broad engineered applications, however their diversity get restricted owing to fluctuations in thermomechanical properties during heating or cooling hence great concern required prior their applications through thermomechanical analysis (TMA). Traditionally, TMA or dilatometry found to be simple, ideal, reliable, sensitive, excellent and basic thermal analytical technique. TMA provides valuable information on thermal expansion, glass transitions temperature (Tg), softening points, composition and phase changes on material of having different geometries simply by applying a constant force as a function of temperature. This compilation highlights the basics and experimental of TMA for both research and technical applications and also provide literature on TMA of polymers, hybrid composites, nanocomposites and their diverse applications.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09b
• /
• pp.1126-1127
• /
• 2006

The kinetics of sintering of Co-Fe materials was studied. The main objective was to establish the effects of iron content and sintering parameters on the microstructure and phase composition of the as-sintered material. Specimens containing from 3 to 25 wt.% iron were sintered in a dilatometer for one hour at 900, 1000 and $1150^{\circ}C$ in either hydrogen or nitrogen atmosphere. The length of specimens during the heating, hold at temperature and cooling steps were monitored to establish the sample's shrinkage. Microstructural observations were carried out on polished and etched transverse sections which were also subjected to the X-ray phase analysis.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09a
• /
• pp.83-84
• /
• 2006

Processing of W-Cu graded materials from attritor-milled W-CuO mixtures is described. The powder reduction steps are investigated by TG and XRD analyses and by microstructural observations (SEM, TEM). Sintering of reduced powder with different compositions is analysed by dilatometry. Sintering behaviour of the graded component processed by co-compaction of a 10/20/30wt%Cu multi-layer material is briefly discussed. Liquid Cu migration is observed and smooths the composition gradient. Perspectives to control this migration are discussed.

• Advances in nano research
• /
• v.16 no.2
• /
• pp.127-140
• /
• 2024

Upon direct/indirect exposure to flame or heat, composite structures may burn or thermally buckle. This issue becomes more important in the natural fiber-based composite structures with higher flammability and lower mechanical properties. The main goal of the present study was to obtain an optimal eco-friendly composite system with low flammability and high thermal buckling resistance. The studied composite consisted of polypropylene (PP) and short abaca fiber (AF) with eggshell powder (ESP) and halloysite clay nanotubes (HNTs) additives. An optimal base composite, consisting of 30 wt.% AF and 70 wt.% PP, abbreviated as OAP, was initially introduced based on burning rate (BR) and the Young's modulus determined by horizontal burning test (HBT) and tensile test, respectively. The effects of adding ESP to the base composite were then investigated with the same experimental tests. The results indicated that though the BR significantly decreased with the increase of ESP content up to 6 wt.%, it had a very destructive influence on the stiffness of the composite. To compensate for the damaging effect of ESP, small amount of HNT was used. The performance of OAP composite with 6 wt.% ESP and 3 wt.% HNT (OAPEH) was explored by conducting HBT, cone calorimeter test (CCT) and tensile test. The experimental results indicated a 9~23 % reduction in almost all flammability parameters such as heat release rate (HRR), total heat released (THR), maximum average rate of heat emission (MARHE), total smoke released (TSR), total smoke production (TSP), and mass loss (ML) during combustion. Furthermore, the combination of 6 wt.% ESP and 3 wt.% HNT reduced the stiffness of OAP to an insignificant amount by maximum 3%. Moreover, the char residue analysis revealed the distinct differences in the formation of char between AF/PP and AF/PP/ESP/HNT composites. Afterward, dilatometry test was carried out to examine the coefficient of thermal expansion (CTE) of OAP and OAPEH samples. The obtained results showed that the CTE of OAPEH composite was about 18% less than that of OAP. Finally, a theoretical model was used based on first-order shear deformation theory (FSDT) to predict the critical bucking temperatures of the OAP and OAPEH composite plates. It was shown that in the absence of mechanical load, the critical buckling temperatures of OAPEH composite plates were higher than those of OAP composites, such that the difference between the buckling temperatures increased with the increase of thickness. On the contrary, the positive effect of CTE reduction on the buckling temperature decreased by raising the axial compressive mechanical load on the composite plates which can be assigned to the reduction of stiffness after the incorporation of ESP. The results of present study generally stated that a suitable combination of AF, PP, ESP, and HNT can result in a relatively optimal and environmentally friendly composite with proper flame and thermal buckling resistance with no significant decline in the stiffness.

• Journal of the Korean Society for Heat Treatment
• /
• v.24 no.5
• /
• pp.262-270
• /
• 2011

Carbide precipitation and dissolution behavior at various temperatures during heat treatment has been studied in STD11 cold working die steel through confocal scanning laser microscopy; dilatometry; and X-ray diffraction analysis. The equilibrium phase diagram and phase fractions with temperature were calculated using a FactSage program. Confocal laser microscopic observation revealed that ${\alpha}$ to ${\gamma}$ transformation temperature is near $800^{\circ}C$; M7C3 carbides melt at $1245^{\circ}C$; and the melting temperature of STD11 is near $1370^{\circ}C$. XRD results indicated that the M23C6 carbides dissolve in the matrix if austenitized at over $1030^{\circ}C$; while the M7C3 carbides remain up to $1200^{\circ}C$ although their amount decreases. The calculated equilibrium phase diagram showed good agreement with experimental results on carbide dissolution and phase transformation temperatures.