Ti-50Ni(at%) and Ti-40Ni-10Cu(at%) alloy powders have been fabricated by ball milling method, and their microstructure and phase transformation behavior were investigated by means of scanning electron microscopy/energy dispersive spectrometry, differential scanning calorimetry (DSC), X-ray diffractions and transmission electron microscopy. In order to investigate the effect of ball milling conditions on transformation behavior, ball milling speed and time were varied. Ti-50Ni alloy powders fabricated with the milling speed more than 250 rpm were amorphous, while those done with the milling speed of 100rpm were crystalline. In contrast to Ti-50Ni alloy powders, Ti-40Ni-10Cu alloy powders were crystalline, irrespective of ball milling conditions. DSC peaks corresponding to martensitic transformation were almost discernable in alloy powders fabricated with the milling speed more than 250 rpm, while those were seen clearly in alloy powders fabricated with the milling speed of 100 rpm. This was attributed to the fact that a strain energy introduced during ball milling suppressed martensitic transformation.

The solid state reaction by mechanical alloying(MA) generally proceeds by lowering the free energy as the result of a chemical reaction at the interface between the two adjacent layers. However, Lee et reported that a mixture of Cu and Ta, the combination of which is characterized by a positive heat of mixing of +2kJ/mol, could be amorphized by mechanical alloying. This implies that there exists an up-hill process to raise the free energy of a mixture of pure Cu and la to that of an amorphous phase. It is our aim to investigate to what extent the MA is capable of producing a non-equilibrium phase with increasing the heat of mixing. The system chosen was the ternary (x=35, 10). The mechanical alloying was carried out using a Fritsch P-5 planetary mill under Ar gas atmosphere. The MA powders were characterized by the X-ray diffraction with Cu-K radiation, thermal analysis, electron diffraction and TEM micrographs. In the case of x=35, where pure Cu powders were mixed with equal amount of pure Ta and Mo powders, we revealed the formation of bcc solid solution after 150 h milling but its gradual decomposition by releasing fcc-Cu when milling time exceeded 200 h. However, an amorphous phase was clearly formed when the Mo content was lowered to x=10. It is believed that the amorphization of ternary powders is essentially identical to the solid state amorphization process in binary powders.

In this study, the characteristics of gas atomized Mg-3wt%Al-1wt%Zn-1wt%MM alloy powders under vacuum condition were investigated. In spite of the low fluidity and easy oxidation of the molten magnesium, the spherical powders could be successfully produced by using a modified three pieces nozzle attached to the gas atomization unit. It was found that most of the solidified powders less than 50m in diameter were single crystal and the solidified structure showed a typical dendritic morphology due to supercooling prior to nucleation. The secondary dendrite arm spacing decreased as the size of powders decreased. The Mg-Al-Ce intermetallic compounds with chemically stable phase were found in the interdendritic regions of -Mg. It is considered that formation of the chemically stable phase may possibly affect to improve the corrosion resistance. Therefore, it is expected that the materials formed of these Mg-Al-Zn-MM alloy powders shows better mechanical properties and corrosion resistance due to the structural refinement.

Ti-45.2at.%Ni-5at.%Cu and Ti-40.2at.%Ni-10atat.%Cu alloy powders were fabricated by gas atomization process. The microstructures, Shape, hardness and phase transformation behaviors of the powders were investigated by means of optical microscopy, scanning electron microscopy, micro-hardness measurement, x-ray diffraction analyses and differential scanning calorimetry. The hardness of the Ti-Ni-XCu alloy powders decreased as Cu-content increased. The x-ray diffraction analyses were carried out for powders without heat treatment, and those that treated at 85 for an hour in a vaccum state( torr) and then quenched into ice water. The intensity of B phase increased with heat treating. The monoclinic B martensite was formed in the Ti-Ni-XCu alloy powders during cooling.

자자들은 최근 비고용 Cu-Ta계의 기계적 합금화(Mechanical Alloying) 방법을 이용하여 이계에 있어서 비정질상의 형성에 대한 구조적 확인을 중성자 회절과 EXAFS(Extended X-ray Absorption Fine Structure)의 실험결과로 부터 얻었다. Cu-Ta계와 같이 혼합 엔탈피(Heat of Mixing: δ Hmix)가 정인계에 있어서 비정질상 형성에 대한 연구는 구조적인 측면 뿐만 아니라. 시료의 전자물성에 대해서도 많은 연구가 되어야만 할 것으로 사료된다. 따라서 본 논문에서는 120시간 MA방법으로 제작한 시료에 대하여 초전도 천이온도 및 X선 광전자분광 실험에서 얻은 가전자대 구조의 전자물성을 측정하고, 그 결과로부터 이종원자 Cu와 Ta간의 결합은 화하결합에 의한 생성임을 확인하였는데, 이들 결과로부터 120시간 MA를 행하여 얻어진 시료는 확실하게 비정질 합금임을 알 수 있었다.