Microstructure And Mechanical Properties Of In Situ TiZr-based Amorphous Matrix Composites Enhanced By Dendrites

TiZr-based Bulk metallic glasses(BMGs)have excellent properties at ambient temperatures,including their ultrahigh strength,large elastic limits,high hardness,outstanding corrosion and excellent wear resistance.However,their high brittleness at room temperature has so far prevented them from being considered for real structural applications.Mthods by tailoring alloy composition and altering the content of Nb are effective ways being employed to solve this problem.Alloy systems(Ti40.4Zr27.7Be15.6Cu6.3)(90+x)/90Nb10-x(x = 6,4,2,0,-2,-4 and-6)are choosen as the object of this reach,and seven in situ β dendrites enhanced TiZr-based bulk metallic galss matrix composites(BMGMCs)with different Nb content are fabricated.The constitution of phases,glass forming ability(GFA),microstructure and mechanical properties,and deformation mechanism of these BMGMCs are studied by XRD,DSC,SEM and TEM.Research found that the volume fraction and size of dendrites are influenced by Nb content,which is increased with increasing Nb content.During the compressive tests of these BMGMCs(Ti40.4Zr27.7Be15.6Cu6.3)(90+x)/90Nb10-x(x = 6,4,2,0,-2,-4 and-6),the ultimate strength and plasticity enhanced with the increase of volume fraction and size of dendrites.Ultimate strength and plasticity of Ti37.72Zr25.85Be14.55Cu5.87Nb16 exceeded 2890 MPa and 45 %,respectively.During the tensile tests of these BMGMCs(Ti40.4Zr27.7Be15.6Cu6.3)(90+x)/90Nb10-x(x = 6,4,2 and 0),the yielding strength and ultimate strength decrease with the increase of volume fraction and size of dendrites.And Ti40.4Zr27.7Be15.6Cu6.30Nb10 possesses the high ultimate fracture and plasticity strength,which are 1428 MPa and 7.3 %,respectively.The plastic deformation capacity is enhanced with the introduction of bcc dendrites.The true stress-stain curves of both compression and tension are divided into three stages which are elastic stage,work-hardending stage and softening stage.The work-hardening stage and softening stage prolonged with the increase of Nb content,illustrating the promotion of plasticity.The shear bands are impeded by β dendrites resulting in the production of multiple shear bands or the bend of shear bands which are the mechanism of the enhancement ofstrength and plasticity.By the analysis of TEM and HRTEM,a large number of lattice distortions,dislocations,and shear steps are formed in deformed BMGMCs,leading to the high strength and plasticity are also the reseaon of high strength and plasticity.