Al-8Fe-2Mo-2V-1Zr alloys were prepared by the gas atomization/hot extrusion and the melt spinning/hot extrusion. For the gas atomized and extruded alloy, equiaxed grains with the average size of 400 nm and finely distributed dispersoids with their particle sizes ranging from 50nm to 200nm were observed. For the melt spun and hot extrusion processed alloy, refined microstructural feature consisting of equiaxed grains with the average size of 200nm and fine dispersoids with their particle sizes under 50nm appeared to exhibit a difference in microstructure. Strength of the latter alloy was higher than that for the former alloy up to elevated temperatures.

본 연구에서는 고온용 고강도 Al 합금을 제조하기 위해 Al-Cr-Zr 복합금속분말을 attritor에서 300rpm의 회전속도로 20시간 동안 기계적 합금화방법으로 제조한 후 진공 고온 압축성형하였다. Al-Cr-Zr 합금의 미세구조 및 조직관찰은 XRD, TEM 등을 사용하여 분석하였고, 열적 안정성은 열적 노출시간에 따른 미소경도측정을 통하여 조사하였다. 진공 열간 압축성형 되었을 때 MA Al-Cr-Zr 합금의 이론 밀도의 97%에 이르는 조밀화르 f보였으며, 300˚C에서 100시간 열처리 한 경우에는 경도변화가 거의 없었고, 500˚C에서 100시간 열처리한 경우에도 감소가 6% 이내로 우수한 열적 안정성을 나타내었다. 이와 같은 MA Al-Cr-Zr 합금의 우수한 열적 안정성은 기계적 합금화에 의해 Al 기지 내에 미세하고 균일하게 분산된 Cr과 Zr이 고온 성형과 열처리 과정에 의해 Al3Zr, Al13Cr2의 금속간 화합물들의 형성되었으며, 열처리 후의 이 합금의 최종 결정립 크기는 150mm 크기 이하이었다.

Al-Cr-Zr nanocomposite metal powders were prepared by mechnical alloying (MA) in order to develop aircraft structure materials with lighter weight and lower cost than the conventional Ti and Ni alloys. The morphological changes and microstrutural evolution of Al-6wt.%Cr-3wt.%Zr nanocomposite metal powders during MA were investigated by SEM, XRD and TEM. The approximately 50m sized Al-Cr-Zr nanocomposite metal powders has been formed after 20 h of MA. The individual X-ray diffraction peaks of Al, Cr and Zr were broadened and peak intensitied were decreased as a function of MA time. The observed Al crystallite size by TEM was in the range of 20 nm, which is a simliar value calculated by Scherrer equation. The microhardness of Al-Cr-Zr nanocomposite metal powders increases alomost linearly with increase of the processing time, reaching a saturation hardness value of 127 kg/ after 20 h of processing. The intermetallic compound phase of in the matrix was identifed by XRD and TEM.

The theoretical optimum quaternary composition for improving the thermal stability of Al-Ti alloy was recently proposed. On the basis of the suggestion, quaternary Al-Ti-V-Zr alloy powders corresponding to the optimum compositions, one of which belongs to the region of the smallest lattice misfit between the matrix and the precipitates and the other belongs to the region of the smallest rate constant of coarsening, were prepared by mechanical alloying and the powders were vacuum-hot-pressed at under the pressure of 800 MPa. The thermal stability of the specimens was evaluated by hardness testing after isothermal aging up to 400 hrs at various temperatures. The decrease of hardness of Al-Ti-V-Zr alloys was smaller than that of Al-Ti alloys. It was considered to be due to the formation of type and type quaternary precipitates having smaller lattice misfit than and the increase of volume fraction of All0v during the isothermal aging. The quaternary Al-Ti-V-Zr alloys corresponding to the smallest lattice misfit showed the most improved thermal stablilty and it was mainly considered to be due to the formation of All0v.