Effect Of Particle Size Mixture On Mechanical Properties Of SiCp/Fe Composites Using Finite Element Simulation

Particle reinforced iron matrix composites(PRIMCs)have high strength,high wear resistance and excellent elevated temperature properties.Mechanical properties and strengthening mechanism of PRIMC do not only depends on the components of the phases,but also on the size,content,shape and distribution of reinforced particles and the features of the interface between particles and matrix.It was found that particle size had a significant effect on mechanical properties of SiCp/Fe composites from experiments.Moreover,mechanical properties of the composites reinforced by different-sized particle mixture were better than those of single-sized particle reinforced SiCp/Fe composites.In this work,the effects of single size(5,10,16,21,28,40?m)particles and size mixture(5+10,5+16,5+21,10+16,10+21,16+21?m)particles on mechanical properties of the SiCp/Fe composites are studied using a revised finite element(FE)model based on Taylor non-local strain gradient plasticity theory,with the SiC volume fraction of 20%.The results show that using the Taylor revised unit-cell FE model to simulate tensile test,the particle strengthening effect on SiCp/Fe composite becomes stronger when the particle size decreases.It indicates that this Taylor model can takeover the shortage of the traditional FE model,which cannot deals with the intrinsic size effect.Furthermore,using a Taylor three zone unit-cell model considering the effect of thermal residual stress,it is found that the existence of thermal residual stress does not change the phenomenon of the better strengthening with smaller particles,but it increases the composite stress significantly.Using a Taylor revised plane-strain model to simulate the tensile test of SiCp/Fe composites,the tensile strength of the composite reinforced by 16?m SiC particles is the best one,then that of the composite by 28?m,followed by 5,10 and 40?m particle ones.As compression is observed in the matrix near the particles in the composites reinforced by 16 and 28?m particles,it indicates that,the matrix can be well protected during the loading and the load bearing by this size particle is larger than that of the others.Meanwhile,the increase of matrix stress means that the matrix strengthening effect increases with the particle size decreases.Moreover,the results by the Taylor three-zone model shows the compression in the matrix of 16 ?m reinforced composite is significantly reduced when the thermal residual stress appears.It is also found that when the particle is smaller,the shear performance of the composite increases generally but the strengthening effect is less obvious than that in tensile loading.The shear stress of the composites increases slightly,but a greater stress concentration appears in the thermal stress area near the interface,which would be likely to cause interfacial debonding for a smaller particle reinforced composite.Based on the single-sized Taylor modified model above,a multi-sized particle mixture Taylor model is established innovatively by overlapping the effect of each single-sized particle stress field into the matrix.This multi-sized Taylor model has been proved by the experimental data of 10+21?m particle reinforced SiCp/Fe composite.After using this model to simulate the tensile properties of a mixture-sized particle reinforced SiCp/Fe composite,the results show that the size-mixture strengthening only occurs on the 5+10,5+16,5+21,10+21 ?m reinforced SiCp/Fe composites,but not on 10+16 and 16+21?m ones.It indicates that not all size-mixture particles perform the mixture strengthening.Moreover,the size-mixture strengthening effect for 5+16?m reinforced one is the best.Meanwhile,it is also found that the size-mixture strengthening for 5+21 ?m one is greater than that for 16+21?m,which indicates that the mixture of two better performanced single-sized particles may not be get a better size-mixture strengthening.Using the Taylor three-zone model,the results show that the existence of thermal residual stress can reduce the size-mixture strengthening effect as well.It is found that the shear properties of all composites reinforced by the size-mixtured particle can be strengthened.Compared with that of the 10+16?m mixture reinforced one,the shear strength of the 5+21?m reinforced composites is better,which implies that the mixture of larger and smaller particles may be a more promising mixture.In this study,we are trying to obtain the optimal mechanical properties of particle reinforced metal matrix composite system by adjusting particle size and to achieve to design materials from microstructural level.