The Research On Microstructure And Mechanical Properties Of Bulk Amorphous Alloys And Composites

In this paper, in order to improve the plasticity of bulk amorphous alloys and composites at room temperature, the high content of zirconium (Zro.72Cu0.28)100-xAlx (x=0,2,4,6,8,10,12,14) alloy rods, the diameter of2mm,4mm and6mm (Zr0.72Cu0.28)88Al12amorphous alloy ladder sample,(Zr0.72Cu0.28-xAgx)88Al12(x=0.002,0.004,0.002,0.004,0.01) alloy rods, and Ti4oNi4oCu2o bulk metallic glass composite rods were prepared by suction casting of copper. The influence rule of alloy elements, cooling rate and annealing temperature on microstructure and mechanical properties of bulk metallic glass and composites were analysed. The results show that:(1) The glass forming ability, microstructure and mechanical properties of (Zr0.72Cu0.28)100-xAlx(x=0,2,4,6,8,10,12,14) alloy with different aluminum content were analyzed. The results show that:with the increasing of the Al content, The glass forming ability was gradually improved, volume fraction and grain size of brittle CuZr2phase were gradually decreased, and the distribution was more uniform, it was amorphous structure when x=12,14. The room temperature compression strength and plastic strain of alloys increased firstly and then decreased with the Al content increasing, the maximum compressive strength (σbc) and plastic strain (εp) are1773MPa and7.45%when x=12. The fracture mode of alloys were transformed from splitting to shear fracture.(2)(Zr0.72Cu0.28)88Al12alloy ladder sample were prepared by suction casting of copper, effects of different cooling rates on the microstructure and mechanical properties of which were studied. The results show that:alloy specimens with different cooling rates were amorphous structure, but the internal atoms configuration had changed. With the size increasing, in other words, the cooling rate decreasing, the plastic strain of the alloys was decreased, and the compressive strength increased firstly and then decreased. The sample with diameter of2mm had the maximum room temperature plastic strain of9.23%. The sample with diameter of3mm had the best comprehensive mechanical properties, compressive strength of1773MPa and plastic strain of7.45%.(3) The glass forming ability and compressive mechanical properties on (Zr0.72Cu0.28-xAgx)88Al12(x=0.002,0.004,0.006,0.008,0.01) amorphous alloy with different Ag added were analyzed, and preliminary study the correlation between microstructure and serrated flow and compression plasticity of amorphous alloys. The results showed that:The glass forming ability were improved to some extent with micro Ag adding. With Ag content increasing, the compressive strength increased firstly and then decreased, and compared to the original alloy composition had improved in different degrees, all of alloys except x=0.008, which composition compressive strength reached more than1800MPa, plastic strain were more than10%, The most significant effect of improving where x=0.004, the compressive strength and plastic strain increased from1773MPa and7.45%of the original component to improving the1911MPa and22.46%; fracture morphology shows that, the more the number of the shear band and the smaller of the space between shear band and the more complicated, the better plastic and compressive strength. To some extent, microstructural inhomogeneity of amorphous alloy improved the compression plasticity, with the increasing of plasticity, serrated statistical distribution transform pake shape into monotonically decreasing trend.(4) Effects of different annealing temperature(150℃、250℃、350℃,0.5h) on microstructure and mechanical properties of Ti4oNi4oCu20bulk metallic glass composite were investigated. The results show that, B2-TiNi and B19-TiNi were precipitated in as-cast and annealing samples, and volume fraction and grain size of precipitated phase increased after annealing; compressive strength and plastic strain first increased and then a slight declined with the increasing of annealing temperature, but better than the cast specimens, compressive strength and plastic strain increased from2247MPa and11.4%of as-cast alloy to2541MPa and19.5%of150℃,0.5h annealing alloy. It shows that the suitable annealing temperature can obviously improve the mechanical properties of Ti-based bulk metallic glass composite.