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To obtain the diffusion coefficient of nitrogen in Fe-C alloys, the 0-3% C-Fe alloy was nitrided by the liquid drop nitriding method in the temperature range of 650 C- 850 C. The main results observed are: (1) The frequency factor Do of nitrogen in 0-3%C-Fe alloy; Do(mC) = 1.17 exp[-1.08(mC)]㎠/sec (2) The activation energy Q of nitrogen in the alloy; Q(mC)= 27.2 exp [30.7(mC)]Kcal/mole (3) And finally, the diffusion coefficient of nitrogen in 0-3%C-Fe alloy is D_(N)= Do(mC) exp[-Q(mC)/RT] ㎠/sec
The effect of carbon and silicon on the hardness of nitrided iron at the temperature range of 650℃- 850℃ was investigated, In the case of carbon added iron, the peak hardnesses and surface hardness were increased but the thickness of nitrided layer was decresed than the nitrided pure iron, In the case of silicon added iron, the internal hardness and surface hardness were decreased than the carbon added iron.
Studies on the X-ray stress measurement have been made in various kinds of nitrided iron specimens. The relation between the hardness measured mechanically and the stress measured by X-rays is Considered. The main results observed are: (1) Nitrided pure iron has the tendency of increaing residual stress with, the increasing time duration of nitriding, (2) Carbon steel has the tendency of decreasing residual stress with the increasing time duration of nitriding treatment. (3) Both of the above cases showed the same results that the hardness increases with the time duration of nitriding treatment.
Transformation characteristics have been investigated in liquid nitrided iron by measuring electrical resistivity. Preliminary microstructure studies have also been made for the Fe-N compound and diffusion layer. An anomalous resistivity peak was observed at about 25 μ and 30 μ of the nitrogen compound and diffusion layers to the nitrogen-martensitic transformation. In the case of the magnetic transformation of nitrogen austenite, the resistivity peak was observed in the various nitrogen compounds and diffusion layers.
The Wear Characteristics of Al-Si alloys were investigated with various Si contents by using the not-dispersed alloys and uncoated-graphite dispersed alloys. Uncoated-graphite dispersions were accomplished by Vortex method carrying 1 hr. heating at 400℃ on uncoated-graphite. Wear loss were increased by increasing Si contents at the elevated final load. Hyper-eutectic alloys showed higher wear resistance values at the small final load of 2.1㎏ and 3.2㎏, but at the more increased final load, hypo-eutectic alloys showed higher wear resistance values than hyper-eutectic alloys. The property of wear resistance of uncoated-graphite dispersed Al-Si alloys showed more good values than not-dispersed alloys. This peroperty of increased war resistance were resulted from lubricating action of dispersed graphite.
To obtain the diffusion coefficient of nitrogen in Fe-Si. alloys, the 0-5%Si-Fe alloy was nitrided by the liquid drop nitriding method in the temperature range of 650 C-800 C. The main results observed are : (1) The diffusion coefficient of nitrogen in pure iron is D_(N)= 1.02 x 10^(2) exp [(-27,200)/RT]. (2) The frequency factor D_(0) of nitrogen in 0-5%Si-Fe alloy; D_(0) (mSi) = 1.17 exp [2.65 (mSi)]. (3) The activation energy Q of nitrogen in the alloy; Q(mSi) = 27.21 exp [23.92 (mSi)]. (4) And finally, the diffusion coefficient of nitrogen in 0-5%Si-Fe alloy is D_(N)= D_(0) (mSi) exp [-Q(mSi)/RT].
Liquid nitriding is being used for machine parts to improve fatigue strength and resistance to wear and seizure in carbon steel. The difference in matrixes with pearlitic, troostitic or martensitic structure in carbon steel has an important effect on nitriding. In the present work, carbon steel with different matrixes were nitrided by a liquid nitriding process at 570℃ for 1-8 hrs for a basic study on the nitriding of carbon steel. A white compound layer and diffusion zone were obtained by nitriding. The compound layer consisted of ε(Fe_(2-3)N) and r'(Fe₄N) nitrides. The total nitrided depth '(compound layer + diffusion zone) in the troostitic steel was greater than those of other steels cwing t o the high diffusion velocity of nitrogen. The relationship between surface hardness and nitriding time can be obtained as follows: In pearlite + ferritic matrix, hardness of surface increased from 210Hv to 640 Hv for 1 hr nitriding time and then decreased do 350Hv and 320 Hv for 4 and 8 hrs of nitriding time, respectively. In martensitic matrix, hardness of surface decreased from 819 Hv to 380 Hv for 1 hr nitring time and then increased slowly to 650 Hv for 5 hrs nitriding time.
Using FT-IR, we measured the infrared emissivities of the nonferrous metal samples(zinc, Cu. Al, brass) which we fabricated. After measurement, we found that the infrared emissivities of the samples increased along with the temperature of the samples, and in that experiments, the emissivities we measured were well close to the calculated values of total nomal emissivities of the samples. Also, more the roughness of the sample's surface increase, more infrared emissivity of the was higher, and the emissivity curve decreased to the temperature of the sample.
The effects of the surface roughness of CdTe gammaray detector chips on the electrical characteristics of Au/n-CdTe Schottky barrier have been investigated using the Schottky diode prepared with he surface roughness in the range of 0.1∼0.5㎛. Measured for the diode are the electrical resistance characteristics, the potential barrier height and the electrical noise. The dynamic resistance is observed to decrease exponentially as R_d=370exp(-9.94ㆍRa)with the surface roughness(Ra) of the CdTe wafers. The potential barrier hight shows an exponential decay like ∮_B=0.88exp(-0.75ㆍRa) with the increase in roughness while the electrical noise shows a linear growth.
In order to get basic thermodynamic informations about shape-memory alloys, the samples, (Cu_(93-x)Zn_x)Al_7, were prepared in the argon gas at the temperature 1150℃. The investig ons for density, specific heat, latent heat, entropy, activation enthalpy, shape memory effect, phase transformation temperature, crystal structure and kinetics have revealed the following results for these samples : 1) these shape-memory alloys have one way memory character and 99 percentage recoveries 2) these alloys have body-centered tetragonal structure below A_s points and body-centered cubic structure above A_f points 3) the phase-transformation temperatures of these alloys are directly proportional to the Zn content 4) the densities of these alloys are about 8.1g/㎤ ; specific heat, 0.1㎈/g ; latent heat, 5㎈/g ; entropy, about 0.016㎈/gK and activation enthalpy, 32.75 K㎈/mole.