The Research On Synthesis And Mechanical Properties Of In-suit Dendrite/amorphous Matrix Composites

In this paper, in-suit dendrite/amorphous matrix composites were successfully fabricated by copper injection casting based on the composition optimized and process adjustment. XRD analysis, microstructure observation, DSC thermal analysis and TEM observation were used to analysis microstructure morphology and composition. Using INSTRON5985 type electronic universal testing machine and separated Hopkinson pressure bar test materials mechanics performance under different strain rates and different diameter size. To reveal the deformation mechanism of in-suit dendrite/amorphous matrix composites, the fracture morphology was observed by SEM.The structure of Ti48Zr20Nb12Cu5Be15 amorphous composites is amorphous matrix and in-suit dendrite crystal phase. Obvious strain rate hardening effect was found under quasi static and dynamic compression. The compressive strength and fracture strain is 1780 MPa and 27% aboved under the condition of quasi static compression tests. The fracture is shear fracture which is characterized by vein patterns, with the increase of strain rate, a large amount of shear slip steps and coordinate deformation is the main cause of high compressive strength and fracture strain; under dynamic compression, the compressive strength and fracture strain is higher than 1556 MPa and 16%, A large area of alloy melt, fragmentation and the expansion of shear bands and the speed of deformation does not match in high strain rate lead to the lower the compressive strength and fracture strain under dynamic compression; Quasi-static compression specimens of different diameters tests show that the material has a significant size effect, with the decrease of the specimen diameter, compressive strength and fracture strain of the sample is increasing, the distribution of a large number of shear bands and the dislocation in dendrite phase is the main reason for the small size with high strength and ductility.The research of different Ag content of(Ti48Zr20Nb12Cu5Be15)100-xAgx in-suit dendrite/amorphous matrix composites shows: the addition of Ag can improve the amorphous formation ability, change the endogenous dendrite morphology, size and composition, with the increase of Ag content, the endogenous dendrite size and volume fraction of dendritic phase decreased.(Ti48Zr20Nb12Cu5Be15)97.5Ag2.5 in-suit dendrite/amorphous matrix composites have excellent mechanical properties than Ti48Zr20Nb12Cu5Be15 under quasi-static and dynamic compression conditions, the quasi-static compression strength have rise by 18% to 19.7%, the fracture strain has raised 16.5% to 16.5% increase; Dynamic compression strength and the fracture strain of the material also have very big margin improvement.Tensile experiments showed that: necking phenomenon was found in the process of tensile, compared with the microstructure of Ti48Zr20Nb12Cu5Be15 in-suit dendrite/amorphous matrix composites, large fracture deformation and break elongation was found in(Ti48Zr20Nb12Cu5Be15)97.5Ag2.5 in-suit dendrite/amorphous matrix composites because of larger areas shear lips and fiber region, dimples is more uniform and dimples is greater depth.To in-suit dendrite/amorphous matrix composites, the volume fraction of in-suit dendrite phase, size distribution and morphology have a significant impact on the performance of the material, only with the optimum ratio of the volume fraction and size distribution of in-suit dendrite phase, the material can generate enough shear bands, and in-suit dendrite phase can hinder the movement of the shear bangs, this will increase strength and ductility. In(Ti48Zr20Nb12Cu5Be15)97.5Ag2.5 in-suit dendrite/amorphous matrix composites, the volume fraction and size of the dendrite phase were 78% and 30%, which were less than the the dendrite phase in Ti48Zr20Nb12Cu5Be15 in-suit dendrite/amorphous matrix composites, excessive volume fraction and mature dendritic phase distribution in Ti48Zr20Nb12Cu5Be15 in-suit dendrite/amorphous matrix composites lead to the dendritic phase has little contribution to the number of shear bands and hinder the extension of the shear bands, so the(Ti48Zr20Nb12Cu5Be15)97.5Ag2.5 in-suit dendrite/amorphous matrix composites has superior mechanical property.