The Research Of Cu₅₀Zr₄₂Al₈ Alloy On The As-cast Microstructure And Its Hardness

With processes of magnetic-suspending melting alloy ingots and copper-mold casting technology, the taper shape of Cu₅₀Zr₄₂Al₈ bulk metallic glasses(BMGs) were prepared, the results show that the taper sample with maximum diameters less than 5mm can be obtained. Cu₅₀Zr₄₂Al₈ BMGs have excellent glass-forming ability. The taper shape of sample with bottom diameters close to 10mm and with length 80mm was obtained. The preparative sample be taken along both axis direction and radial direction. X-ray diffraction(XRD) and electron microprobe analysis(EPMA) was used to characterize the evolution of structure, metallograghic microscope (MeF3) was used to characterize the microstructure and micro-sclerometer was used to test microhardness.The study shows that the cooling rate was greet influence on the as-cast microstructure of Cu₅₀Zr₄₂Al₈ alloy. With different rate of cooling, micro-structure of Cu₅₀Zr₄₂Al₈ alloy are different. From the surface to the center, the fully amorphous region,glass/crystal composite and full crystal region exist respectively, The crystal size and the volume fraction increase gradually from the surface to the center, haveing the gradient characteristic. When the sample is investigated by X-ray diffraction continually , crystal phase of Cu₁₀Zr₇ begins to be formed. With the crystal grows up and increases, the plasticity and the elasticity of the sample are obviously reduced, the hardness increase to some extent. The thermal stability of taper shape of sample under different rate of heating are studied by means of DSC. The rate of cooling is different, the test specimen microhardness is different either. To crystal area , hardness is high in center, to amorphous region, the rate of cooling in center is small, hardness is actually high.Excellent mechanical properties as well as low cost of Cu-based bulk amorphous alloys make it possible to be widely used at project in future.