| Title |
Effect of Ambient Temperature on Mechanical Alloying Process in Immiscible Cu - Ta System |
| Authors |
이충효(Chung Hyo Lee); 복영준청(Toshiharu Fukunaga); 수용우일랑(Uichiro Mizutani) |
| Abstract |
The mechanism far the amorphization induced by mechanical alloying(MA) has been studied in the immiscible Cu-Ta system. A mixture of copper and tantalum powders at a composition ratio Ta : Cu=7 : 3 was used. The first 30h of milling essentially results in the reduction in Ta and Cu grain size down to about 100Å without measurable formation of an amorphous phase. The thermally assisted amorphization(TAA) becomes noticeable after 60h of milling. The higher the ambient temperature, the faster the amorphization proceeds. The TAA effect is also observed by annealing a partially amorphous MA powders. The microstructure after 30h of milling is such that fine Cu crystallites are embedded in the finely-grained Ta matrix. Here an interfacial energy contribution is large enough to raise the free energy to that of an amorphous phase. Now high temperature milling or annealing allows an energetically down-hill process to occur. This is most likely responsible for the observed TAA effect in the Cu-Ta system characterized by a positive heat of mixing. (Received August 10, 1992) |