Laser Additive Manufacturing Of In-Situ TiB₂/Al Composite:Microstructure And Mechanical Properties

With the rapid development of aerospace and defense industries,there is a growing demand for products with high performance and complex structure.In-situ TiB₂/Al composite is widely used due to its light weight,high specific strength and specific modulus.However,it's difficult for traditional preparation process to meet the needs of complex structure in the above areas,which is well solved by combining the in-situ TiB₂/Al composite with laser additive manufacturing.The laser additive manufacturing of aluminum is more challengeable due to its poor flowability,high reflectivity,high thermal conductivity and oxidation.Moreover,the microstructure of alloy sample of laser additive manufacturing is characterized as coarse columnar grains,which has a bad effect on mechanical properties.The existence of TiB₂ particles in composite is expected to improve the above status.In order to solve the problem of laser additive manufacturing of aluminum,meeting the growing demand for products with high performance and complex structure in aerospace and defense industries,this project was carried out to study the laser additive manufacturing of in-situ TiB₂/Al composite and its mechanical properties,and the contents are as follows:?1?the alloy and in situ TiB₂/Al composite were compared based on laser additive manufacturing,studying the effect of TiB₂ on the manufacturing of alloy;?2?cast process and laser additive manufacturing were compared based on in situ TiB₂/Al composite,studying the microstructure evolution and strengthening mechanism of mechanical properties of in situ TiB₂/Al composite fabricated by laser additive manufacturing.Research on the laser additive manufacturing of in situ TiB₂/Al composite indicates that coarse columnar grains induced by directional growth is greatly refined with the existence of TiB₂ particles in composite.The laser absorption of TiB₂ is much higher than matrix,which disturbs the strong positive temperature gradient,and the pinning effect of TiB₂hinders the grain growing along the flow direction to make the microstructure more uniform.Moreover,compared to the cast,laser additive manufacturing refines the microstructure greatly,disperses TiB₂ particles,decreases element segregation and dissolves elements extensively due to its rapid cooling rate,and the thermal mismatch stress exists between the TiB₂ and matrix to gather lots of dislocation.Mechanical properties are thus improved,and the strengthening mechanism is as follows:grain refinement strengthening,dispersion strengthening,solution strengthening and dislocation strengthening.