• 한국산업융합학회 논문집
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• 제5권4호
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• pp.361-366
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• 2002

The change of mechanical properties of drawn PP filaments which was treated by isothermally annealed after elevated heating. Measurements were carried out with UTM for mechanical properties. Isothermally heat treatment were carried out $100^{\circ}C$, $120^{\circ}C$, $140^{\circ}C$ for 10min., 30min., 60min, in silicon oil bath. And isothermally heat treatment after elevated heating from $20^{\circ}C$ were carried out $100^{\circ}C$, $120^{\circ}C$, $140^{\circ}C$ for 10min., 30min., 60min., with heating rate of $1^{\circ}C/min$., $5^{\circ}C/min$., $10^{\circ}C/min$. From the results of this study, it found the following facts. Initial modulus and tensile strength were increased with increasing of annealed temperature and time. Also initial modulus of tensile strength of samples which were isothermally annealed after elevated heating from $20^{\circ}C$ were higher than those of isothermally annealed samples.

• 한국산업융합학회 논문집
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• 제6권4호
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• pp.387-392
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• 2003

The change of crystalline structure and mechanical properties of PET filaments were investigated. Samples were treated by isothermally annealed after elevated heating. Measurements were carried out of density gradient tube for crystallinity and UTM for initial modulus and yield stress. Isothermally heat treatment were carried out $100^{\circ}C$, $120^{\circ}C$, $140^{\circ}C$ for 10min., 30min., 60min, in silicon oil bath. And isothermally heat treatment after elevated heating from $20^{\circ}C$ were carried out $100^{\circ}C$, $120^{\circ}C$, $140^{\circ}C$ for 10min., 30min., 60min., with heating rate of $5^{\circ}C/min$., $10^{\circ}C/min$. From the results of this study, it found the following facts. It was found that the crystallinity, initial modulus and yield stress of samples were increased with increasing of annealed temperature and time. Also crystallinity, initial modulus and yield stress of samples which were isothermally annealed after elevated heating from $20^{\circ}C$ were larger than those of isohtermally annealed samples.

• 한국산업융합학회 논문집
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• 제3권4호
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• pp.345-351
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• 2000

The change of crystalline structure of drawn PP filaments were investigated. Samples were treated by isothermally annealed after elevated heating from $20^{\circ}C$. Measurements were carried out with XRD for crystallite size and density gradient tube for crystallinity. Isothermally heat treatment were carried out at the temperature of $100^{\circ}C$, $120^{\circ}C$ and $140^{\circ}C$ for 10min., 30min. and 60min. in dry oven. The isothermal heat treatment after elevated heating from $20^{\circ}C$ were carried out at the temperature of $100^{\circ}C$, $120^{\circ}C$ and $140^{\circ}C$ for 10min., 30min. and 60min. with heating rate of $1^{\circ}C$/min., $5^{\circ}C$/min. and $10^{\circ}C$/min. From the results of this study, it found the following facts. It was found that the crystallinity and crystallite size of (110) plane of sample were increased with increasing of annealed temperature and time. Also crystallinity and crystallite size of samples which were isothermally annealed after elevated heating from $20^{\circ}C$ were higher than those of isohtermally annealed samples.

• 열처리공학회지
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• 제8권4호
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• pp.302-317
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• 1995

After initial structure of AISI 9260 steel is changed into pearlite and martensite, one is isothermally annealed at $700^{\circ}C$ below of $A_1$ transformation point and the other is isothermally annealed at the same condition after 3 cycles of heating and cooling between $680^{\circ}C$ and $780^{\circ}C$ of $A_1$ transformation point. Analyzing the changes of microstructure, mechanical properties and fractography of tension test, we obtained result as follows. The fastest spheroidization rate by changes of initial structure and heat treatment cycles is appeared at the heat treatment cycle which is isothermally annealed after 3 cycles of heating and cooling at below and above $A_1$ transformation point for martensite. At the above condition, the perfect spheroidization structure is appeared after 60hrs and after then, globular carbide is being coarsened. The mean diameter of globular carbide is $2.4{\times}10^{-3}mm$ after 90hrs. The changes of tension strength during spheroidization heat treatment follows Orwan function, ${\sigma}_o={\sigma}_i+Gb/l$, where l is interspacing of carbide particles and at the above condition, ${\sigma}_o=70.48+2.5{\times}10^{-3}/l(kg/mm^2)$. Fractography of fracture of spheroidization structure in tension test is appeared as dimple which is ductile rupture type by nucleation and growth of void, size of dimple is larger and deeper with increasing of heat treatment time.

• 열처리공학회지
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• 제29권2호
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• pp.51-55
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• 2016

The P/M processing of titanium aluminide using amorphous TiAl is developed by which it is possible to overcome inherent fabricability problems and to obtain a fine microstructure. A high quality amorphous TiAl powder produced by reaction ball milling shows clear glass transition far below a temperature at the onset of crystallization in differential scanning calorimetry above a heating rate of 0.05 K/s. We obtained a fully dense compact of amorphous TiAl powders, encapsulated in a vacuumed can, via viscous flow by hot isostatic pressing (HIP). Isothermally annealing of HIP'ed amorphous compact under a pressure of 196 MPa shows a progressive growth of ${\gamma}-TiAl$ phase with ${\alpha}2$ ($Ti_3Al$), which is characterized by increasing sharpness of X-ray peaks with temperature. Fully dense HIP'ed compact of titanium aluminide TiAl shows a high hardness of 505 Hv, suggesting strengthening mechanisms by sub-micron sized grain of ${\gamma}-TiAl$ and particle-dispersion by second phase constituent, ${\alpha}2$.