Mechanical Alloying Of Mg-based Amorphous Alloys

Materials can be classified into distinct species: crystal and amorphous body due to the ranging mode of the atoms. Amorphous materials mainly include oxide glasses, macromolecule polymers, semiconductors in amorphous state and metallic glasses. Because amorphous alloys have many unique physical and chemical properties compared with crystalline alloys, the investigation on such materials has been the foreland of condensed physics and design to new materials.The Mg-Cu series amorphous alloy are prepared by the method of mechanical alloying, studied thoroughly by the method of DTA, SEM, X-ray, and so on.At first, in this paper, the glass forming ability of five alloys with three eutectic compositions and two compound compositions based on the Mg-Cu phase diagram was studied under mechanical alloying conditions. X-ray diffraction results show that all the alloys except for one with eutectic composition formed amorphous alloys. The descending sort of the glass forming ability of five alloys is MgCu2, Mg58Cu42, Mg2Cu, Mg85.5Cu14.5 and Mg22Cu78. According to Davies' criterion, if the amount of MgCu2,GFA -T*is less 0.2 , MgCu2 should be difficult to form amorphous alloy. But in this paper, it shows that its GFA is strongest. Therefore, as a composition criterion of amorphous alloy, Davies' theory is more suitable than Schwarz and Johnson's theory.The structure and the morphologies of the MgCu2 and Mg58Cu42 amorphous powders, prepared by mechanical alloying after different milling times, have been studied by XRD and SEM in this paper. It is showed that Mg and Cu powders can dissolve into each other and the dissolution becomes larger after milling. During the milling process, Mg powders firstly dissolve into the gap of Cu crystal lattice and solid solution with Mg supersaturation is formed. Then, the energy of supersaturation gets large enough to break its stability, and the amorphous alloy is obtained at the end. At the same weight ratio of ball-to-powder, enhancing the velocity of milling can accelerate the formation process of amorphous and the milling time of amorphous formation process is shorten.Influencing of milling parameters on Mg-Cu amorphous alloy prepared by ball milling has been studied in this paper. Composition constitutes, milling parameters such as ball/powder weight ratio, milling time and milling speed, and process control agents are key discussed factors. Results of XRD study showed that composition constitutes, milling parameters and process control agents have similar important influencing effect on glass forming. All the energy transferred to the powder is different for different milling parameters (the ratio of powder and ball , rotation speed , milling time;) and a part of this energy is used in increasing the temperature that decides the kinetic energy and thermodynamic state of the powder after ball milling.