The Research Of Microstructure And Mechanical Properties On Zr-based Bulk Metallic Glass

People are more and more interested in Zr based amorphous alloys,because its excellent mechanical properties and different from the structure of crystalline metal materials.Even the Zr based bulk metallic glasses as structural materials have many excellent properties,there are still some problems.The problem of the brittleness of the bulk amorphous alloy,structural problems of amorphous alloys that has good plasticity and effect of external conditions on the properties of amorphous alloys,all these problems need to be solve.This research work continues our previous researches,and the mechanical properties and microstructure of Zr based bulk amorphous alloys based on the(Zr_0.761Cu_0.147Ni_0.092)92-x Al8+x,(Zr_0.72Cu_0.278Ag_0.002)₈₈Al₁₂,(Zr_0.72Cu_0.165Ni_0.115)88Al12,were measured by X ray diffraction,differential thermal analysis,room temperature compression test and microhardness test.Here are results obtained:?1?By adjusting the Al elements of(Zr_0.761Cu_0.147Ni_0.092)92-x Al8+x amorphous alloy,the(Zr_0.761Cu_0.147Ni_0.092)₉₂Al₁₀ amorphous alloy with large size and great plasticity was obtained.The plastic deformation of the alloy with 3mm diameter was up to15.82%.Moreover,this composition has good glass forming ability that the supercooled liquid region reached 94 K.With the increase of Al content,the yield strength and microhardness of the(Zr_0.761Cu_0.147Ni_0.092)92-x Al8+x alloy increased,reaching the maximum 1713 MPa and 4096 MPa when x reached 6,respectively.?2?Through the calculation of the _mixing enthalpy and _mixing entropy of(Zr_0.761Cu_0.147Ni_0.092)92-x Al8+x amorphous alloy,we found that the ? was close to 1,the better the thermal stability of the alloy is;Through the statistical analysis of the serrated flow behavior of plastic deformation,we found,with the continuing of plastic strain,the more stable the stress drop fluctuation is,the better the plasticity of the alloy is.On the contrary,when the stress drop fluctuation of alloy becomes larger and larger,the alloy becomes more unstable and the plasticity is smaller.Through the micro hardness test of(Zr_0.761Cu_0.147Ni_0.092)92-x Al8+x amorphous alloy samples after corrosion,it was found that the hardness of the hard regions is different from that of the soft regions.And the greater the alloy hardness difference between the soft and hard regions is,the better plasticity of it will be.?3?By means of rapid solidification,we obtained the Zr_0.72Cu_0.278Ag_0.002)₈₈Al₁₂alloy samples with different cooling rates.After the room temperature compressionexperiments on the samples,we found that with the decrease of cooling rate,the plasticity of the alloy decreased obviously,while the strength of the amorphous alloy increased significantly.However,since the 6mm sample was crystallized,the large grain reduced its strength significantly.Through the corrosion and back scattering electron analysis of 2mm diameter specimens which have great plasticity,we found the corrosion surface is similar to the network.By comparing the analysis,the net was produced because the corrosive structure of the alloy was corroded more easily than the substrate.That is,the inhomogeneous microstructure of amorphous alloy.This conjecture was confirmed by nanoindentation tests of(Zr_0.72Cu_0.165Ni_0.115)88Al12amorphous alloy 3mm specimen with better plasticity.?4?After as cast bulk metallic glasses samples with diameter of 2mm and 3mm were subjected to isothermal annealing treatment,they were subjected to room temperature compression test and microhardness test.The results showed that,with the increase of annealing time,the plasticity of 2mm alloy specimens worsen gradually,but the strength increases gradually.However,the ductility and strength of3 mm samples decrease and then increased.It is same to 2mm and 3mmsamples,that the microhardness of the alloy increased with the increase of annealing time,and there is a linear relationship between annealing time and microhardness.