| Bulk metallic glasses(BMG)has a high fracture strength,but the high local shear behavior of BMG under load causes BMG to break directly without obvious macroscopic plasticity.This severely limits the application of BMG in the field of engineering materials,so the research to improve the plasticity of BMG has very high engineering application value.With the development of science and technology,humans have increasingly higher requirements on the performance of materials.In the field of amorphous alloys,there are still many things that need to be studied for the development of amorphous alloys.This paper systematically studied the plasticity lifting principle and plasticity change law of a series of ZrTiNbCuNiBe amorphous composites material from the aspects of forming technology and composition design,as well as the role and connection between the two methods.The microstructure and mechanical properties of the amorphous composite materials after as-cast and semi-solid treatment were compared,and the principle of plasticity improvement of the semi-solid process on the materials was studied.Through the orthogonal experiment method,the optimal semi-solid processing parameters were found,and the change law of the microstructure and properties of the material was found.By changing the Nb content in the alloy system,the effect of the Nb content change on the microstructure and mechanical properties of the as-cast and composite materials after optimal semi-solid treatment was studied.At the same time,the influence of the change of Nb content on the plasticity improvement effect of the semi-solid process was studied.The main results are as follows:(1)semi-solid isothermal treatment cannot change the phase structure of the Zr54.0Ti13.2Nb4.8Cu7.8Ni6.2Be14.0 alloy,but can change the morphology of the microstructure from dendritic to spherulite.The volume fraction of the ductile phase and the macroplasticity of the material were increased,while the microhardness of the material was decreased.The volume fraction and macroscopic plasticity increased by 84%and 152%respectively,the hardness of crystal phase decreased by 56%and that of amorphous substrate phase decreased by 48%.(2)During semi-solid treatment,the diameter of the crystal phase and the holding time follow the Ostwald ripening law(k=1.84 in this article),and the linear relationship between the crystal phase diameter and the holding temperature(the slope of this article is 0.077).As the Nb content is increased,the optimal semi-solid process parameters of the four materials are(800?,100min),(860?,10min),(900?,10min),(940?,10min).The parameters are slightly higher and closer to the solid phase line of the crystal phase.(3)The principle of semi-solid process to improve the plasticity of the material:the process can increase the volume fraction of the crystal phase,and the deformation energy absorbed by the crystal phase increases.The process allows the dendrites to become spherical and grow,and improve the toughness relative to the nucleation ability of the shear band.The large-diameter spherulites have a positive effect on the blocking and propagation of the shear band.The process can reduce the hardness of the microstructure of the material and improve the toughness of the microstructure.(4)As the Nb content is increased,the volume fraction of the toughness phase of the ZrTiNbCuNiBe amorphous composite material is improved.In this study,the maximum volume fraction of the toughness phase is 60%of the semi-solid Zr60.0Ti14.7Nb5.3Cu5.6Ni4.4Be10.0 alloy-Under the same semi-solid process parameters,as the Nb content is increased,the diameter of the spherulites is increased,the shape factor is reduced,and the macroscopic plastic strain of the material is improved.The largest plastic strain is the optimal semi-solid Zr60.0Ti14.7Nb5.3Cu5.6Ni4.4Be10.0 alloy,which is about 26.3%in this paper.(5)As the Nb content increases,the microhardness of the two phases in the material first decreases and then increases.The lowest hardness is the Zr58.5Ti14.3Nb5.2Cu6.1Ni4.9Be11.0 alloy.The hardness of the amorphous substrate is higher than that of the crystalline phase.After semi-solid treatment,the microhardness of the two phases tends to be stable,and the microhardness of the crystalline phase decreases,but in the amorphous substrate phase,the hardness of Zr54.0Ti13.2Nb4.8Cu7.8Ni6.2Be14.0,Zr56.2Ti13.8Nb5.0Cu6.9Ni5.6Be12.5 alloy decreases.The hardness of Zr58.5Ti14.3Nb5.2Cu6.1Ni4.9Be11.0 and Zr60.0Ti14.7Nb5.3Cu5.6Ni4.4Be10.0 alloys increased.(6)As the Nb content is increased,the effect of the semi-solid process on the plasticity improvement of the material is reduced,and the plasticity improvement rate is reduced to a minimum of 67.5%.The research content of this article is that the advancement of Zr-based amorphous composite materials in engineering applications has a positive impact.At the same time,it can be used to guide the semi-solid process improvement of Zr-based composite materials and the optimization of composition design. |
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