| Title |
Thermal Stability and Microstructure of Mechanically Milled Nanocrystalline Al-14wt%Ni-14wt%Mm Alloy Powder |
| Authors |
홍순직(Hong Sun Jig); 이윤석(Lee Yun Seog); 천병선(Cheon Byeong Seon) |
| ISSN |
1738-8228(ISSN), 2288-8241(eISSN) |
| Keywords |
Nanostructure; Rapid solidification; Mechanical milling; Thermal stability; Powder; Microhardness |
| Abstract |
Mechanical milling has been performed for Al-14 wt%Ni-14 wt%Mm(Mm=misch metal) alloy powders rapidly solidified by the gas atomization method. The microstructure, hardness, and thermal stability of the powders were investigated as a function of milling time using X-ray diffraction(XRD), transmission electron microscopy(TEM), Vickers micro-hardness tester and differential scanning calorimetry(DSC) methods. In the early stage of milling, a cold-welded layer with a fine microstructure was formed along the edge of the milled powder (Zone A). The interior of the powder remained unworked (Zone B), resulting in a formation of two-zone microstructure. With increasing milling time, the nanocrystallite size decreased gradually reaching a size of about 10-15 nm and the lattice strain increased reaching a maximum value of about 0.7% after milling for 200 hours. The microhardness of the mechanically milled powder was 132 kg/㎟ after milling for 72 hours, and it increased to 290 kg/㎟ after milling for 200 hours because of the presence of fine nano structured phases. |