Study On Microstructures And Properties Of6061Al Matrix Composites With Various Reinforced Ways

The6vol.%Mg2B2O5w/6061Al composite (W6),6vol.%SiCp/6061Al (P6)composite and (3vol.%Mg2B2O5w+3vol.%SiCp)/6061hybrid composite (W3P3)composite were fabricated by stir casting in this paper. The hot deformation behaviorand workability of W3P3hybrid composite and P6composite were investigated byhot compression tests and processing map technique; The elevated temperaturemechanical properties of as-extruded composites and6061alloy were tested byusing a universal testing machine; The ageing hehavior of6061alloy and W6, P6,W3P3composites in as-cast and as-extruded conditions was investigated by means ofhardness measurement (HV) and DSC analysis; The dimensional stability of6061alloy and W6, P6, W3P3composites in as-extruded and T6heat-treatment afterextrusion was investigated by using dilatometer; The microstructures of compositeswere studied by SEM and OM.The results showed that the W3P3hybrid composite has the best dispersion ofreinforcements among all the composites; There was severe Mg2B2O5wagglomeration and SiCpsegregation in W6and P6composites respectively.The processing map of W3P3hybrid composite exhibits a single hot workingdomain:350-450C/0.0001-0.003s-1(domain#1); Two hot working domains existfor P6composite:(i)300-400C/0.0001-0.003s-1(domain I);(ii)380-450C/0.01-0.1s-1(domain II); The estimated apparent activation energy wasabout224kJ/mol in domain#1for W3P3hybrid composite, and the deformationmechanisms contain dislocation climb controlled creep and grain boundary slidingcaused by DRX in this domain; The estimated apparent activation energies are about177kJ/mol and263kJ/mol in domain I and domain II for P6composite respectively,and the deformation mechanisms is dislocation climb controlled creep in domain I,the deformation mechanisms is cross-slip in domain II.The elevated temperature mechanical properties of as-extruded materials testindicated that the ultimate tensile strength, yield strength and Young’s modulus were the highest for W3P3hybrid composite compared with W6, P6composites and6061alloy under the same temperature; The elongation to failure was the highest for W3P3hybrid composite among all the composites, which was associated with uniformityof reinforcements distribution in W3P3hybrid composite.The ageing hehavior test showed that the SiCp can more effectively improvethe hardness values than Mg2B2O5w; The age-precipitation process of thecomposites was accelerated compared with the6061alloy, The hardness values inas-cast condition were higher than the values in as-extruded condition for the samematerial, the age-precipitation process of the materials in as-cast condition wasaccelerated compared with the materials in as-extruded condition.The dimensional stability test showed that whether the materials in as-extrudedor T6heat treatment after extrusion conditions, the CTE, dL/L0and the width ofhysteresis loops were the smallest for W3P3hybrid composite; T6heat treatment caneffectively reduce the CTE, dL/L0and the width of hysteresis loops for all thematerials; The W6composite presents the smallest magnitudes of residual strain,followed by W3P3hybrid composite after thermal cycling in as-extruded condition;For the materials under T6heat-treatment after extrusion condition, the P6compositepresents the smallest magnitudes of residual strain, followed by W3P3hybridcomposite.