Hot Deformation Of?ZrB₂+Al₂O₃?/6061composites With Reinforcement Network Distribution

In this paper,?ZrB₂+Al₂O₃?/6061 composites with soft matrix surrounded by quasi-continuous network reinforcement based on H-S theory was designed and successfully fabricated.Scanning electron microscopy?SEM?and X-Ray Diffraction?XRD?were used to characterize microstructures of composites.Mechanical properties at room temperature such as tensile strength,hardness,bending strength and fracture properties and density were analyzed.The constitutive equation and processing map were established on the basis of he hot compression tests.200rpm and 2h of low-energy milling process were chosen to mix the B,ZrO₂ and6061 aluminum alloy powders.850^oC and 90 min of holding time were considered to be the best process of the reaction.SEM and XRD show that the full reaction between raw materials have happened to form the ZrB₂ and Al₂O₃ which are quasi-continuous distributed in the region of matrix.After hot extrusion deformation,the reticular structure unit,defection,the size of reinforcements and grain were decreased combining with the increasing density in the composites.Hardness test showed that the hardness of the material gradually increased from the matrix region to boundary of the reinforcement.Also,the hardness increased after extrusion and heat treatment.The tensile test at room temperature shows that the deformation of hot extrusion can increase the plasticity and the tensile strength of composite material at the same time.The strength of the hot extruded composite materials is increased to 233.6MPa,and the plasticity was 16.3%respectively.The hot compression of extruded aluminum matrix composites was studied at various temperatures?350-500??and strain rates(0.001-0.1s^-1).A constitutive equation that describes the flow stress of composite as a function of strain rate and deformation temperature was also determined.According to the relationship between stress and strain,we make processing map technique for thermal processing of materials provides a basis.Rolled composites are rolled in various temperatures and different passes,macro cracks after bending cannot be found in the extruded materials,...