| Being fine, homogeneous and free of melting, the powder prepared by mechanical alloying has applied to develop scattering strengthen-material, magnetic material, high-temperature material, superconductivity material, amorphous, and non-equilibrium material, compound material etc. As a high-tech technology to prepare alloying powder, MA has become a more and more important method for preparing new materials. There are many reports on the preparation and the formation mechanism of binary alloy using MA, but there arc few reports on the study of ternary alloy. To understand MA method further, some investigations are made by both experiment and theory in this paper.Al-Cu-Fe ternary nano-amorphous alloy was prepared using a planetary ball mill. Amorphous can be obtained at certain composition range using ball milling. The size of the amorphous particles decreases with the lengthening of milling time, and reaches several nanometers. Experiment also shows that the mixture powder is well ferromagnetic. The powder Structure was analyzed by EDAX analysis. The amorphous phase is formed from the transformation of super-saturate solid solution, and there is no nuclear formation and grow process.The effects of milling condition on alloying are studied. The adding of process-control agent can effectively keep the powder from sticking to the milling ball and the inner wall of containers. The increase of rotating velocity and the ratio of ball to powder can accelerate the phase transformation and thus shorten the alloying time.The thermal behaviors were studied using DTA. The powders crystallize at about 600℃. As the content of Al is lower than 40 at%, there is only Al2Cu3(Fe) after heat treatment and the particle size is homogeneous, while the content of Al is higher than 40 at%, the product is complex and the particle size changes greatly.Up to now the mechanical alloying process can't be described precisely in theory due to its complex. In this paper, milling balls are presumed to distribute In the container as simple body-centered cubic. On the base of this simple model, therelationship is set up of the velocity of milling ball, the average motion range and the frequency of collision with the velocity of planetary ball mill, the ratio of ball to powder, the size of milling ball and the parameters of ball milling.On the base of milling ball interaction during milling process, the powder height of each collision can be calculated. If the impact of milling ball takes as Hertz elastic collision, the maximum real strain and the maximum tangential strain are obtained as follows,e,..,ln[h, /(h0 —vrcos6/2)]= vrsin6/h0 — /q, T2RT2 /2Om~h,Jwhere s , , p, v are maximum real strain, the maximum tangential strain, friction coefficient and the velocity of milling ball.During the process of mechanical alloying, the temperature-rise of powder is an important parameter. The relation of rise of temperature with collision velocity, collision angle and the powder materials is as following,i~T=95%xV1~~c2[ /4;; VbS1fl6+CoC~ +K4Z/(n+1)]where C,, is the specific heat of the powder, a~, k and n are constants. The calculation results show that the rise of temperature is close link with the rotating of miller. As the velocity of miller is higher certain value, the temperature of powder can reach the melting point of some metals, which is consist with the experiment result. |
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