Study On Preparation Technology And Properties Of TiB₂ Particles Reinforced A1-18%Si Matrix Composites

Particle reinforced aluminum matrix composites possess several additionaladvantages such as light weight, weal-resisting, high specific strength, high specificmodulus, high temperature-resisting and so on. So they are widely used in spacenavigation, aviation, advanced weapons, electronic industries and car manufacturing.Based on the thermodynamic analysis of Al-TiO₂-KBF₄-Na₃AlF₆ reaction system,the TiB₂P/Al-18%Si composites were manufactured by the directional melt reactionin-situ synthesis process. The phase composition, solidification microstructure, thedistribution of TiB₂ particles on the matrix and hardness of the composite wereinvestigated respectively by using XRD, OM, EPMA, SEM and other modemequipments. The effects of reaction temperature, reaction time, stirring intensity on thedistribution of reinforcing particles were studied. The mechanical properties and drywear property of the composites have also been tested．The nature and mechanism ofthese characteristics have been analyzed. The main results are as follows:(1)Experimental results show that the optimization parameters for the fabricationof TiB₂/Al-18%Si composites by using of Al-TiO₂-KBF₄ -Na₃AlF₆ reaction system areas following:the initial reaction temperature is between 1000℃to 1050℃, the amountof reactant added 6wt%,adding the reaction mixture as lump, the reaction time is30min,making a large stiring intensity．(2)Microstructure analysis shows that the grain size ofα-Al and eutectic Si ofTiB₂P/Al-18%Si in situ composite is smaller than that of Al-18%Si matrix alloy.(3)XRD, SEM and EPMA analysis indicated that there were Al, Si, and TiB₂phase in the composite. The in-situ TiB₂ particles are less than 1.0μm, and uniformlydistribute in the Al-18%Si matrix alloy.(4)Mechanical property tests show that the hardness and tensile strength ofTiB₂P/Al-18%Si composites were higher significantly than that of Al-18%Si matrixalloy respectively. And increased with the increase of the mass fraction of the particles,while the elongation decreased．With the 6% in-situ particulate, the values for tensilestrength and hardness reached to 82.4 and 173.8MPa, increased by 40.7% and 32.2%respectively compared with those of Al-18%Si matrix alloy. Morphology analysis forthe fracture surface of the composites showed that the fracture mechanism is brittlefracture. (5)Dry sli ding wear tests at room temperat ure shows that the wear resist ance ofthe composites is superi or to that of its matrix alloy. The wear mechanis ms of thecompositesis adherence wear and abrasi on wear．...