The Research On Thermal Processing Stability Of Several Amorphous Alloys

It is an important step towards industrial application of amorphous alloy to process amorphous alloy in the supercooled liquid region. The size of the thermal stability of amorphous alloy in its supercooled liquid region is an important basis for the decision whether such an amorphous alloy suitable for machining and the choice of processing technology. In this paper, the thermal stability and crystallization kinetics of bulk amorphous alloys Zr65Cu15Al10Ni10, Cu47Ti34Zr11Ni8, Zr60Nb5Cu20Fe5Al10 and Mg68Zn28Ca4 have been investigated by X-ray diffraction method(XRD) and differential scanning calorimetry(DSC). Zr65Cu15Al10Ni10 amorphous alloy powder was prepared by broken milling amorphous strip. Extrusion block was prepared by warm rolling powder in its supercooled liquid region. Metallurgical and fracture morphology of the extrusion block was studied by confocal microscopy and scanning electron microscopy. The mechanical property of extruded block was studied by uniaxial compressive tester and hardness tester. The main experimental results and conclusions are listed as follows:By Kissinger equation, Owaza model and Augis-Bennett model, the four amorphous alloy crystallization activation energy was calculated. The crystallization activation energy Mg68Zn28Ca4 is the smallest indicated its poor thermal stability. The other three amorphous alloy has a larger crystallization activation energy. By Johnson-Mehl-Avrami equation method, the nucleation of the amorphous alloys was analyzed. The three dimensional thermal processing window of the amorphous alloys was established, according to the three-dimensional thermal processing window the maximum processing temperature and heating time can be determined.The thermal processing window show Zr65Cu15Al10Ni10 amorphous alloy does not crystallized in 300 s at 422℃. The shape of the powder particles prepared by broken milling is irregular cube. There is a slight crack and fresh fracture traces on the powder surface. Extrusion Block remains amorphous structure, without crystallization. At low extrusion pressure, asperity interface exists between the amorphous alloy powder. Metallurgical bond between the two particles tiny region occurred. At high extrusion pressure, amorphous alloy powder particles occurs rheology and asperity grain boundaries disappear. The fracture morphology of extrusion block showed the fracture of bulk material is brittle fracture.