발간논문

Home > KJMM 논문 > 발간논문

keyword :

Directional solidification experiments were conducted on Al-Ni eutectic alloys to investigate the growth mechanism and the mechanical behavior of Al-A1₃Ni composites. The effects of the growth rate and the addition of magnesium on the composite structures and the mechanical properties were investigated. Dendritic and composite structures are superior to colony structure as regards the mechanical strength. If the growth condition favors the formation of dendritic or composite structures, a decrease in G/R ratio (G: temperature gradient, R: growth rate) will cause an increase in tensile strength.

keyword :

A study has been made of electrowinning of manganese dioxide using a titanium anode. The electrolysis conditions such as concentrations of manganese ion and sulfuric acid, current density, electrolysis temperature and time, and surface roughness of anode have been examined, laying an emphasis on their mutual relationships and their effects on the current efficiency. The current efficiency was found to be decreased with increasing concentration of sulfuric acid. The optimum current density was 1-1.5A/d㎡. The effective electrolysis time increased with increasing concentration of manganese sulfate and decreasing concentration of the sulfuric acid. It was also important to raise the temperature above 90℃ in order to continue the electrolysis for a long time. It was observed that the anode potentials and bath voltages increased sharply when the deposited manganese dioxide layer stripped partially from the titanium anode. These phenomena were discussed based on the development of residual stresses in manganese dioxide deposits and anodization of the titanium anode.

keyword :

Serrated flow or Portevin-Le Chatelier effect is made through the intermittent locking of mobile dislocations by diffusing solute atmosphere within certain temperature and strain rate range. This dynamic strain ageing phenomena appear as the serrated flow curve which has one to one correspondence with Luders band propagation. The frequent locking of mobile dislocations induces enhanced dislocation multiplication and high work hardening. Second phase precipitation on the uniform and dense dislocation substructure does not deteriorate the durability of the dynamically strain aged material significantly while improving its strength. Such a thermomechanical treatment is reviewed on a low carbon steel, high strength low alloy steels, and 7075 aluminum alloy.

keyword :

Effect of vanadium contents and tempering temperature on the mechanical properties of low carbon vanadium steel was studied with V content ranging from zero to 0.16% and tempering temperature of 500℃, 600℃ and 700℃. As the results, hardness, tensile strength, yield strength and wear resistance were increased with the increase of vanadium content and the maximum value was shown when 0.106% of vanadium was added and tempered at 600℃ for 1 hr. Vanadium carbides were dispersed in ferrite and randomly precipitated at dislocation sites. The improvement of the mechamical properties was interpreted in terms of grain refinement and locking of dislocations due to vanadium carbides.

keyword :

Two types of aluminium-composite reinforced with steel fiber were prepared by a casting method; one was fabricated with Zinc-coated steel fiber, and the other the Zinc-uncoated steel fiber. The effect of fiber orientation on strength of these two kinds of composite was investigated. In the case of Zinc-coated steel fiber, the strength of the composite increased linearly with increasing fiber volume fraction, independent of fiber orientation. However, in the case of Zinc-uncoated steel fiber, the strength of the composite with steel fiber parallel to tensile axis increased linearly with increasing fiber volume fraction but the strength of the composite with steel fiber aligned 45 and 90 degrees to the tensile axis decreased linearly with increasing fiber volume fraction.

keyword :

keyword :

keyword :

keyword :

keyword :