Study On Microstructure And Mechanical Properties Of Semi-solid Processed Ti₄₈Zr₁₈V₁₂Cu₅Be₁₇Bulk Metallic Glass Matrix Composites Rods With Different Diameters

Bulk metallic glasses?BMGs?have been favored by relevant experts at home and abroad because of their unique properties such as high hardness,high strength,high elastic limit?2%?and excellent corrosion resistance.However,it is unsatisfactory that during the compression loading process at room temperature,most metallic glasses exhibit brittle fracture due to the rapid expansion of their internal highly localized shear bands.The main method to overcome this problem is to introduce a second plastic phase to develop metallic glass matrix composites?BMGMCs?.One of which In-situ synthesised dendritic toughening method,it is considered to be a relatively simple and effective method for its ability in effectively hindering the rapid expansion of the shear band.In this study,we draw Ti₄₈Zr₁₈V₁₂Cu₅Be₁₇7 BMGMCs?a Ti-based BMGMC?into rods with diameters of 2 mm,4 mm,and 6 mm by use of copper mold suction casting in conjunction with semi-solid processing methods.The microstructure of the sample was analyzed and characterized by metallographic microscope,XRD,SEM,EDS and TEM.The effects of copper-die-casting-size and semi-solid heat treatment on the thermophysical properties,intrinsic properties and mechanical properties of the BMGMCs were individually studied by DSC,nanoindentation and room temperature compression experiments.The main conclusions were as follows:?1?With the increase of the size of the copper mold,the?-Ti-phase grain size of BMGMCs also becomes larger;changing the size of the copper mold suction casting has no obvious influence on the thermal physical properties of the composite material in this study,and the glass transition of the BMGMCs with different diameters occurs around 620 K in the as-cast state.?2?the plasticity of the BMGMCs with different diameters?2 mm,4 mm,6 mm?reached the best after being kept at 900°C for 10 min in our research,which were14.1%,16.4%and 18.0%,respectively.?3?The BMGMCs tend to exhibit higher plasticity when the shape factor of the?-Ti grains become lager,conversely,when the shape factor is low,the composites always exhibit room temperature brittleness.?4?The yield strength of BMGMCs and the grain size of?-Ti phase in BMGMCs in as-cast state and after holding for 10 min at 900°C obey the relationship of?_y=1443+3046D^-11 and?_y'=1465+4062D^-1,respectively.?5?All the BMGMCs possess higher plasticity and ultimate strength after holding at 900°C for 10 min when compared with the as-cast state,and in which T_6ss exhibits the highest plastic strain of 18.0%and highest ultimate strength of 2204MPa.