Reaction Mechanism And Mechanical Properties Of Particles Reinforced Copper Matrix Composites Fabricated In-situ From(Al-)Ti-B-Cu Systems

In this paper,the TiB2 particles reinforced copper matrix composites were fabricated in-situ from Ti-B-Cu and Al-Ti-B-Cu systems.The reaction products were observed by SEM,TEM,FIB-SEM and EDS,and the phase composition was identified by XRD.The reaction mechanism of the two systems were explored combining thermodynamic analysis and DSC analysis.Results showed that Ti-B-Cu and Al-Ti-B-Cu systems can react spontaneously and generate TiB2 particles reinforced copper matrix composites.In addition,the tensile properties and friction and wear properties were also studied.Study of reaction mechanism showed that Ti-B-Cu system consisted two reaction steps during sintering process.The apparent activation energy was 453.94 KJ/mol and 1139.85 KJ/mol,respectively.Al-Ti-B-Cu system consisted three reaction steps.The apparent activation energy was 997.68 KJ/mol,823.09 KJ/mol and 2560.71 KJ/mol,respectively.Microstructural analysis showed that the reinforcement content and milling time have a great influence on the microstructure of the composites.The composites with reinforcement volume fraction of 20 vol.%and milling time of 8h possessed relatively uniform microstructure,and the TiB2 particles were fine and dispersed.Under the same conditions,the TiB2 particles in Al-Ti-B-Cu system were much smaller than those in the Ti-B-Cu system.However,some Al3Ti remained at Cu grain boundaries.Study of tensile properties showed that the Ti-B-Cu(20 vol.%)system with 8h milling possessed the largest ultimate tensile strength of 318.39MPa,which was enhanced by 44.72%compared with pure copper.The elongation was 8.31%.Many small dimples were observed in the tensile fracture,indicating that the material possessed good toughness.Study of friction and wear properties showed that composites possessed the best friction and wear properties with the reinforcement volume fraction of 20 vol.%.When TiB2 content was 10 vol.%,the reinforcing effect was unsatisfactory.When TiB2 content was 30 vol.%,the reinforcements aggregated and brittle fracture was easy to occur.The wear mass lost of the composites increased with the increase of load.However,with the increase of the sliding rate,the wear mass lost decreased firstly and then increased.There are furrows and abrasive dust accumulation on the wear surface.The main wear mechanism were abrasive wear,adhesive wear and oxidation wear.