| The laser microzone metallurgy method uses a system based on laser additive manufacturing.The high-energy laser beam output by the laser system is used to heat the pre-mixed powder in the groove at a fixed point,so that the mixed powder in the groove is quickly melted in a small area,and no external stress is achieved.The rapid self-convection metallurgy of the melting zone can achieve high-throughput preparation of alloy materials under laser non-equilibrium rapid solidification conditions,which can provide a fast and efficient new material research and development idea for the research of alloying mechanism in laser additive manufacturing.In this study,laser microzone metallurgy technology was used to realize the rapid preparation of titanium-based composites based on boron addition by adding boron element and taking advantage of its in-situ self-generated TiB enhancement phase characteristics,and systematically study the amount of boron addition and related laser non-equilibrium fast.The effect of solidification process parameters on the solidification structure of boron-titanium-based composites,the precipitation morphology and distribution characteristics of TiB reinforcement phase,and the effect of boron addition on the microstructure and microdomain properties of the matrix.Explore the formation conditions and formation conditions of quasi-continuous network TiB On this basis,the alloying mechanism of titanium-based composites based on boron addition is clarified,and the correlation knowledge map of boron addition,laser non-equilibrium metallurgical parameters,microstructure characteristics and micro-area properties is established,which is based on boron The high-throughput preparation of the added titanium-based composite material and the application of laser additive manufacturing lay a scientific foundation.The main conclusions are as follows:(1)The microstructure changes and influencing factors of TiB/Ti-6Al-4V composite materials with different boron addition contents were studied.The TiB/Ti-6Al-4V material prepared by laser microzone metallurgy has good metallurgical quality without macro segregation,poor fusion,and cracks.The TiB enhancement phase in the TiB/Ti-6Al-4V composite material prepared with laser power P=500W is mainly distributed in the form of grain boundary enrichment,which inhibits the growth of β grains.The boron content is increased from 0.1wt.% to 0.5wt.%,and the β grains have been significantly refined.It is worth noting that when the boron content is increased to 0.5wt.%,the addition of boron affects the distribution of solute Al and V,which intensifies the segregation of Al and V elements and promotes the formation of dendritic structure.(2)Under different process parameters(Laser power P,Pulse width t),the precipitation law,microstructure characteristics and process characteristics of TiB enhanced phase are studied.The three TiB/Ti-6Al-4V composite materials designed in this study(with boron addition of 0.1wt.%,0.3wt.%,and 0.5wt.%)are all prepared under different process parameters to obtain a quasi-continuous network structure TiB,but the precipitation conditions of the quasi-continuous network TiB of different composition materials are not consistent.With the increase of boron content,the critical power for the precipitation of quasi-continuous network TiB decreases,indicating that the increase of boron content is beneficial to the precipitation of quasi-continuous network TiB.The reason is: under high power conditions,the convection in the laser microzone metallurgy molten pool is strong,which avoids the segregation of boron in the molten pool.The TiB reinforcement phase is uniformly distributed in the β-Ti phase,and according to the particularity of the structure of TiB itself,when the number of TiB reinforcement phases reaches a certain level,they are finally distributed in the form of a quasi-continuous network structure.(3)The micro-area performance test and analysis of TiB/Ti-6Al-4V composite materials obtained under different conditions.It was found that when the TiB reinforcement phase appeared in the form of a quasi-continuous network structure,the size of the TiB reinforcement phase was greatly reduced,and the microhardness of the corresponding composite material was significantly increased.In addition,the microhardness of TiB/Ti-6Al-4V composites is closely related to the precipitation content of TiB reinforcing phase.Through the micro-indentation experiment and the micro-indentation reverse algorithm,it is concluded that the yield stress of the laser microzone metallurgy Ti-6Al-4V+0.3wt.%B alloy has also been significantly improved when the quasi-continuous network TiB structure is obtained.(4)Through the establishment of the laser microzone metallurgy Ti-6Al-4V+0.3wt.%B alloy process-structure-hardness map,The comprehensive characterization of the laser microzone metallurgy Ti-6Al-4V+0.3wt.%B alloy process-microstructure-hardness has laid a solid foundation for further material design. |
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