Study On The Preparation Mechanism And Mechanical Properties Of In-situ Synthesis Of (TiB₂+TiC) Two-phase Reinforced Aluminum Matrix Composite By Selective Laser Melting

TiB₂reinforced aluminum matrix composite material has the advantages of low density,high specific strength,good high temperature performance,and strong fatigue resistance.It has broad application prospects in high temperature wear-resistant materials and other fields.This paper uses selective laser melting(SLM)technology,while using in-situ chemical reaction under the action of high-energy laser beam,in-situ synthesis of TiC and Ti B₂ceramic dual-phase reinforced aluminum matrix composites.The raw materials used are Ti powder,B₄C powder and Al Si10Mg alloy powder,that is,using the high-temperature in-situ chemical reaction of Ti and B₄C powder under the action of laser beam and the principle of rapid solidification of the molten pool,in-situ synthesis of TiC and Ti B₂dual phase by SLM method Reinforced aluminum matrix composite material.The process window was found and the composite materials with different composition ratios were studied to obtain the appropriate composition ratio,and the influence of process parameters on the composite materials was studied to finally explore the mechanism of in-situ chemical reaction.The results showed that the aluminum matrix composite containing TiC and Ti B₂was successfully prepared with the laser power of 160-200W,scanning speed of600-1200mm/s,scanning interval of 0.07mm and powder layer thickness of 0.02mm by using the ball-milling mixing process to prepare the mixed powder with the total mass percentage of Ti and B4C of 0.7%,5.7%,11.5%and 17.2%.With the increase of Ti and B₄C composite powder content in the composites,TiC and Ti B₂reinforcing phase content in the composites gradually increased,and the microhardness of the composites gradually increased,and the fracture characteristics changed from ductile fracture to brittle fracture.When the content of Ti and B₄C composite powder was0.7%,the aluminum matrix composite synthesized in situ by selective laser melting had the highest tensile strength,with the maximum value of 417 MPa.When the total mass percentage of Ti and B₄C in the composite powder was 17.2%,the scanning speed had no significant influence on the phase composition of the composite material,but the laser power had some influence on the phase composition of the composite material.With the increase of the laser power,the content of Ti₃Si C₂in the composite material gradually decreased.When the laser power is 180 W and the scanning speed is 1200 mm/s,the tensile strength is the highest,but the change of laser process parameters does not change the tensile fracture characteristics of the composite.When Ti and B₄C are only present in the reaction system,only TiC and Ti B₂are generated by laser in-situ chemical reaction.When Al Si10Mg powder is increased and the composition ratio is higher than 5.7%,in addition to TiC and Ti B₂,Ti₃Si C₂phase is generated by laser in-situ chemical reaction in addition to Si elements in the matrix and TiC reactions generated.