Fabrication Processing,Mechanical And Electrical Properties Of Cu-coated TiCp/Al Composites

Particle-reinforced aluminum-based composites combine the advantages of ce-ramic particles and aluminum alloy matrix,exhibiting high specific strength and spe-cific modulus,good thermal conductivity and electrical conductivity,and wear rsistance.However,the wettability between the ceramic particles and aluminum is dif-ficult,leading to a nouniform distribution of particles and poor interfacial bonding with the matrix when stirring casting method is used.This issue limits the further improve-ment of mechanical and electrical conduction properties of Al matrix composites.In this paper,heterogeneous deposition method was used to coat the surface of Ti C parti-cles with Cu(TiCp-Cu).TiCp-Cu particles reinforced 1070 aluminum matrix(TiCp-Cu/Al)composites were fabricated by stir casting method,and then extruded to form rods(?9.5 mm)at 500?.The effects of coating solution ratio,p H value on the morphology of Cu coatings were studied.Moreover,the changes of the composite mi-crostructure,mechancal and electrical properties vs.the processing conditions were established in views of the discussion on the property mechanisms.The main conclu-sions are following:The effects of the p H value of the heterogeneous reaction system and the volume ratio of Cu:TiCp were studied.When the p H value increases from 1 to 4 or the Cu:TiCp ratio increases from 50:50 to 80:20,the particle size and thickness of the Cu coating increase,in this conditions,the Cu particles will gather into branches.The initial mor-phology of TiCp is spherical,and the p H of the reaction system is 2-3 and Cu:TiCp=65:35,the Cu coating particles of TiCp-Cu composite particles obtain uni-form(about 300 nm)and moderate thicness.The effects of TiCp-Cu particle addition and extrusion deformation on the micro-structure of aluminum matrix composites,particle distribution and interface of the composite are analyzed.TiCp with Cu coated performance good wettability with alu-minum melt,so that the distribution uniformity is higher when the addition amount is less than 4wt%,but when particles added more than 4wt%lead to decrease in distribu-tion uniformity and interface bonding.Squeeze deformation can reduce casting porosi-ty,and redistribute TiCp-Cu particles along the rheological direction,thus improve uniformity and interface bonding strength of composite particle in the matrix,but it is difficult to change the distribution state of particle agglomeration zone under high ad-dition.The relationship between the mechanical properties of TiCp-Cu/Al composites,the amount of composite particles and the state of thermal processing are revealed.With the increase of TiCp-Cu composite particles,the hardness,tensile strength,and compressive yield strength of the composite increase first and then decrease,while the elongation changes on the contrary.Compared to the matrix,the mechanical properties of AMC are significantly improved by direct strengthening,fine-grain strengthening,and Orowan strengthening.When the reinforced particles'addition amount is 2 wt%,the extruded hardness and tensile strength of TiCp-Cu/Al composites are higher,which are 36.3 HV_0.5 and 101.4 MPa respectively.Low-temperature annealing,aging and an-nealing+aging reduced the mechanical properties,but the elongation increased.Com-pared to extruded state,the elongation of the composite with 2 wt%addition in anneal-ing state at 240?/6h increased from 27.3%to 33.2%.The electrical conductivity changes of TiCp-Cu/Al composites under different conditions were studied.With the increase of TiCp-Cu particles from 0 to 2 wt%,the conductivity of the composite material first decreases and then increase;when the addi-tion amount is increased to 4-5 wt%the electrical conductivity decreases,and when aluminum matrix composites annealed in 240?or aging below 200?the electrical conductivity increase.The Cu coating can be used as a conductive channel to offset the adverse effects of TiCp and its interface on the conductive properties of the substrate,so that the conductivity of the extruded composite material at an additive amount of 2wt%can reach 61.3%IACS,which is close to the value of the substrate(61.5%IACS).TiCp-Cu/Al composites with an additive amount of about 2 wt%have high mechanical and electrical properties when annealed at 240?/6 h,with tensile strength,elongation,and electrical conductivity reaching 100.2 MPa,33.2%and62.7%,respectively IACS,the tensile strength is 39.2%higher than the matrix,and the conductivity is close to the 62.8%IACS of the matrix.After the composite material is annealed at 240?/6 h+(170?/10 h+200?/6 h)aging treatment,the electrical con-ductivity is increased to 63.1%IACS,and the tensile strength is 96.6 MPa.