Study On Preparation And Properties Of Iron-based Amorphous And Al/Ti Laminated Composites

Different from traditional crystal materials,amorphous alloys are considered as potential materials because of their short-range ordered and long-range disordered internal structures.Among them,iron-based amorphous alloys have attracted much attention due to high strength and hardness,good elastic modulus,good corrosion resistance,excellent soft magnetic properties and strong price advantages.However,the iron-based amorphous alloy ribbons are mainly used in the field of electric power at present.The critical size,preparation process and room temperature brittleness limit their mechanical properties.Considering the high hardness and multi-element characteristics of iron-based amorphous ribbons,they are expected to expand the application of amorphous alloys in large-scale structural materials by introducing them into the laminated structure as strong layers or reinforcing phases.In this paper,iron-based amorphous ribbons Fe_73.5Si_13.5B₉Cu₁Nb₃(at%)with high hardness were used as the main bearing layers.Iron-based amorphous/Al laminated composites and iron-based amorphous/Zn laminated composites were prepared by vacuum hot pressing diffusion method.X-ray diffraction(XRD)was used to calibrate the phases of amorphous ribbons and diffusion layers;the microstructure and element distributions of the composite were characterized by OM,SEM,EPMA,EDS and TEM,and the intermetallic phases were analyzed;vickers hardness tester was used to measure the hardness of each layer and the interfaces;the bending strength and impact toughness of laminated samples were measured by mechanical experiments,and the influence of thickness ratio(thickness of Al foils or Zn foils:thickness of amorphous ribbons)on mechanical properties was analyzed.In the process of preparing amorphous matrix laminated composites,composites showed good interface bonding state.When the iron-based amorphous ribbons were combined with Al at 530?,they would transform into amorphous nanocrystals.The hardness of the nanocrystalline layer(?1100 HV)is higher than that of the original amorphous ribbon(?800HV).The diffusion layers are mainly composed of Fe₄A₁₃(Fe Al₃)phase and granular Fe Al₂Si phase.The bending strength of the laminated samples is 341 MPa and the impact strength is50 J/cm².The iron-based amorphous ribbons can completely retain the amorphous morphology when compounded with Zn at 420?,and the diffusion layers are mainly composed of Fe Zn₁₃ and Fe Zn₁₀ phase.With the decrease of the layer thickness ratio,the ductile brittle transition occurs.When the volume fraction of amorphous alloys in the laminated samples is about 50%,the three-point bending strength of the samples is 155 MPa.The retention of appropriate amount of ductile metal can effectively improve the comprehensive mechanical properties.In the two reaction systems,the Fe element involved in the diffusion originates from the surface layer of the amorphous ribbons in contact with the ductile metal,and the internal structure is not destroyed,which indicates that the size of the amorphous strip can be expanded by lamination.Subsequently,iron-based amorphous ribbons are introduced into the preparation of Al/Ti laminated composites as reinforcement phase,and Al foils were on both sides of the amorphous ribbons.It was found that the iron-based amorphous ribbons were completely consumed and the amorphous lines were left.Some metal Al diffused into the amorphous line and pushed the intermetallic compounds Fe Al₃ to both sides.The results showed that the irregular massive and dispersed intermetallic Fe Al₃ phases were distributed in the diffusion region,and the Al₃Ti layers formed by diffusion were uniform and straight.The residual metal Al can not only enhance the toughness of the structure,but also wrap the granular and massive intermetallic compounds formed by the diffusion reaction.Thus,the sample can form a compact whole.When the thickness ratio of the original Ti foils to Al foils is 1,the bending strength and impact toughness of the amorphous reinforced Al/Ti laminated composites reach746 MPa and 40 J/cm²,respectively.When the layer thickness ratio is 2:1,the tensile strength of the sample is up to 303 MPa.The results show that the cracks are mainly initiated in Fe Al₃phase and propagate along the weak interfaces between massive Fe Al₃ and flat Al₃Ti layer,and the failure occurs under the synergistic effect of multiple tunnel cracks and delamination cracks.When the iron-based amorphous ribbons participate in the fabrication of structural parts in the form of reinforcement phase,rich elements can be used to change the laminated structure.As a result,the crack initiation positions and propagation paths are changed,and the performance defects of the existing laminated composites are also improved.