Study On Microstructure And Properties Of Fe-based Amorphous/stainless Steel Composites Prepared By Selective Laser Melting

Metal matrix composites(MMCs)are composed of metal and reinforced materials.The reinforcement phases include particles,whiskers or fibers.While it is difficult to manufacture complex parts and porous structure from MCC by traditional methods.As an important representative of metal additive manufacturing technology,selective laser melting(SLM)use laser to melt selective powders zone and can produce complex porous component.This study focuses on the key scientific issues in the preparation and forming of Fe-based amorphous and its reinforced composites.In this work,SLM process parameters control and original material modification are studied,including four aspects:Forming defects and control methods of amorphous alloy,the influence of amorphous alloy on the microstructure and properties of MMC,composition optimization of amorphous alloy as a new reinforcement phase and lattice structure manufacturing.The study results reveal the evolution rule and control method of microcracks and crystallization of Fe based amorphou sprepared by SLM,establish the powder composition design theory of Fe based amorphous reinforced stainless steel composite for SLM process characteristics,clarify the strengthening mechanism of mechanical and corrosion resistance of Fe based amorphous/stainless steel composite,and propose the design method of composite lattice structure and SLM manufacturing technology.It provides theoretical guidance for the application of SLM in lightweight components.The stress distribution was controlled by different scanning strategies to suppress cracks in FeCoCrMoCBY amorphous alloys,and the relationship between cracks and equivalent stresses obtained by simulation under different scanning strategies was analyzed and revealed.The hardness of FeCoCrMoCBY amorphous alloy prepared by SLM can up to 1081.6±51.4HV₃.The FeCoCrMoCBY/stainless steel composite is prepared with the addition of 10 wt.%FeCoCrMoCBY amorphous alloy.The tensile strength of the composite 1090 MPa compared with 819 MPa of stainless steel.Meanwhile,the passivation interval of composite increased from 0.918V_{Ag/Ag Cl} to 1.185V_{Ag/Ag Cl}.At the same time,the pitting time is longer,from 488 s to 1668 s,result in a greatly improved corrosion resistance.Due to the mechanism of deoxidization and purification of Y element in SLM preparation process of FeCoCrMoCBY/stainless steel composite,the formed Y₂O₃ chains just only are on the surface of composite,resulting in higher mechanical properties and corrosion resistance.But the microcracks occur at the interface of the molten pool due to the flow of Y₂O₃ with the reinforcement content increase.On this basis,the modified FeCoCrMoCB amorphous powders are prepared and as the new reinforcement phase for the stainless steel.The content improved to 20 wt.%and the tensile strength increased much.The distribution of the mechanical properties is between 1200-1400MPa.A three-period minimally curved Diamond lattice structure was fabricated using the developed composite material.The results showed that the lattice structure has a tendency of brittle fracture,but the Young's modulus and yield strength have been improved.Comparing four lattice structure with different volume fraction,the performance increased with the volume fraction increased,indicating that the structural lightness and mechanical load of the lattice structure component have high designability,which provides theoretical basis of materials and design manufacturing for subsequent engineering applications.