High Temperature Deformation Behavior Of Al-7Si/?10SiCp+xTiB₂? Hybrid Composites

Hybrid reinforced aluminum matrix composites is a kind of material with great potential improving the comprehensive properties of the composites by synergetic enhancement through selecting and integrating the properties of reinforced components.However,its development and application were restricted by the unmachinability.In this paper,the flow behavior of Al-7Si/?10SiCp+x TiB₂??x=3,5,8?composites prepared by powder metallurgy at high temperature was investigated through Gleeble hot compression experiment.The experimental parameters were set to true strain 0.6,deformation temperature 350-500°C and strain rate 0.001-1 s^-1.The hot workability and deformation mechanisms of the composite material was investigated by Electron Backscattered Diffraction?EBSD?,Transmission Electron Microscope?TEM?,Scanning Electron Microscope?SEM?combined with the constitutive equation and the processing map.True stress-true strain curve showed that the deformation resistance decreaseed with the increase of temperature and the decrease of strain rate.The Arrhenius equation is adopted to describe the functional relationship between the deformation temperature?strain rate and the flow stress of Al-7Si/?10SiCp+x TiB₂??x=3,5,8?composite material.The thermal deformation activation energies of Al-7Si/?10SiCp+x TiB₂??x=3,5,8?composites with different TiB₂ contents were calculated as 265.123 kJ/mol,269.654kJ/mol and 263.967 kJ/mol,respectively.Based on the dynamic material model,the processing map of Al-7Si/?10SiCp+x TiB₂??x=3,5,8?composite under the strain of 0.1-0.6 were constructed.The result showed that the total area of the instability zone at 0.6 increased gradually,the maximum dissipation efficiency reduced significantly and the optimum deformation condition changed from low temperature high strain rate zone to high temperature low strain rate zone with the increase of TiB₂ content at the same deformation condition.For the Al-7Si/?10SiCp+3TiB₂?composite material,its instability region and best processing range were 440-500°C,0.135-1 s^-1 and 395-405°C,0.368-1 s^-1 respectively and its maximum dissipation efficiency was 32%.For the Al-7Si/?10SiCp+5TiB₂?composite material,there were three instability region,350-440°C,0.001-0.015 s^-1;350-380°C,0.368-1 s^-1 and 480-500°C,0.607-1 s^-1,the best processing range was 490-500°C,0.011-0.030 s^-1 and the maximum dissipation efficiency was 28%.For the Al-7Si/?10SiCp+8TiB₂?composite material,its instability region and best processing range were 350-500°C,0.135-1 s^-1 and 485-500°C,0.001-0.030 s^-1 respectively and its maximum dissipation efficiency was 23%.The deformation driving force of Al-7Si/?10SiCp+x TiB₂??x=3,5,8?composite materials was improved with the addition of TiB₂ nanoparticles by exacerbating dislocation pile-up.At the same deformation condition,the softening mechanism changes from DRX into DRV,with the increasing of TiB₂.The main softening mechanism is DRX and DRV when the content of TiB₂ is 3wt.%and 5wt.%,and the main softening mechanism is DRV when the content of TiB₂ reach to 8wt.%.