The Research Of Plastic Deformation And Thermal Fatigue Behavior For SiCp/7090Al Composites

The ratio of strength,stiffness,low density and other advantages,is the brake disc materials have great potential.The experimental materials of high temperature plastic deformation constitutive equation and hot processing map of theoretical basis of the rolling process and the effect of heat treatment on Microstructure and properties of SiCp/7090 Al composite materials based on crack propagation and fatigue life prediction of composite mechanical thermal fatigue,for the further development of deformation and fatigue properties of aluminum matrix composites provide a basis for plastic the aluminum matrix composites.The main experimental results are as follows:(1)In this paper,the constitutive equations and processing map of SiCp/7090 Al composites based on hot compression,get the most suitable temperature range of composite thermal processing for 400?-475?,the strain rate range of 0.0001s-1-0.001s-1,and through the observation on the microstructure of composite materials to verify the processing map.The calculation of the constitutive model and experimental value comparing the maximum average error is 9.59%,can accurately describe the stress behavior of nodular cast iron hot compression flow,which provides the basic data and theoretical basis for the optimization of composite material of high temperature plastic forming process.(2)The optimum rolling process and heat treatment process.The rolling temperature is 450?,the microstructure of SiC composite particle agglomeration basically eliminated,the distribution uniformity of the highest reaches the maximum,the maximum tensile strength is 455 MPa,elongation of 5.33%.solid solution temperature is 475?,holding time 2.5h,material hardness value reached the maximum value of 164.3HV.the tensile experimental material by tensile strength of the optimal solution treatment for 465 MPa,elongation of 9.6%.on the optimal solution of the plate material aging treatment,when the aging temperature is 140?,for the time5 h,the microhardness reaches the maximum value 205.8HV..The tensile strength of the material is 605 MPa and the elongation is 5.6%.after the optimum aging treatment.(3)Because the substrate thermal stress state is residual tensile stress during compression stress and tensile stress cycle change,as for the thermal fatigue test,the matrix and the interface can be formed of accumulated plastic strain damage,resulting in fatigue crack initiation.In the course of the experiment found that the lines in Charpy V notch adorable root mechanical thermal fatigue crack,in the same cycle,with the rise of the upper temperature crack length will be longer,the crack growth rate will be faster;at the same temperature,no heat treatment of the specimen compared to the samples after heat treatment early cracks,the crack growth rate will be faster.(4)In the expansion of SiC particles and the Al matrix of the fatigue crack,fatigue crack extension in 7090 Al matrix is mainly for non continuous expansion,the crack propagation into the Al matrix is blocked,under the action of thermal stress,to "bypass" way through the Al matrix;because the fracture strength of SiC particles is larger than SiC and the interfacial bonding strength between aluminum matrix,so the thermal fatigue crack mainly in the interfacial debonding form through the SiC area.(5)The experiment proves that the material fatigue crack growth in the range of Paris had the longest time,growth rate is relatively slow,in the crack propagation into steady-state tear,crack growth rate almost exponentially,until the fracture.The stress and strain concentration in the hot heat,Charpy V notch damage type seriously,the fatigue life prediction for a minimum of 5 million 581 thousand times.