Numerical Simulation Reasearch On The Stir Casting Of SiO₂/Al Particle Reinforced Composites

Particle reinforced aluminum matrix composites,which is lighter,better wear resisite nce and high intensity,has been widely used in aerospace,mechanical industry and so o n.This paper is mainly focused on Aluminum Matrix composites that is reinforced by SiO₂ particel.The SiO₂ is a kind of ceramic particle which exibits many advantages a mong other particle,including low cost,low density and low thermal expansivity.It is well known that the uniform distribution of reinforced particle in the Alumin um matrix has a significant influence on the mechanical properties of the whole comp osites.Stir casting,which is low cost and simple operating conditions,has been widely a dopted to produce the particle reinforced aluminum matrix composites.In this paper,the numerical simulation method and stir casting experiments are both conducted to investi gate the distribution of added particle in the liquid aluminum during stiring process.Two-Phase numerical model was adopted to simulate mixing process of SiO₂ parti cle and liquid aluminum in different stirring condition.Accoring to the particle distribut ion in the liquid aluminum,the influence of different stirring parameters on the particle distribution was discussed in different chapter.The results showed that diagonal-blade i mpeller can generate a bettter liquid aluminum fluid field than verticle-blade impeller,which is more suitable for particle dispersing process.And the “dead region” came into being due to excessively large diameter of stir tank,massive particle deposited aroun d the bottom and wall of the stir tank.Then the injection position of particle hardly af fectted particle distribution eventually,but it can influence efficiency of mixing proces s.Furthermore,a large amount particle deposited in the bottom of liquid aluminum field with high impeller position,and also deposited in the middle of liquid aluminum field with low impeller position,moreover,”dead region” emerged in this two situation.At las t,improper agitation speed also lead to ununiform distribution of particle in liquid alu minum fluid.So the control of stirring parameters during mixing process is really impo rtant to get an uniform distribution of SiO₂ particle in the composites.According to numerical simulation results,stir casting experiments was conducted with different agitation speed,including 200 rpm,400 rpm and 600 rpm.Diameter of th e stir tank is 120 mm,impeller was placed 40 mm above the bottom.After the mixing process was done,upper mixture of fluid aluminum and particles was taken to make m etallographical samples.The metallographical quantify method was adopted to quantify uniformity of the particle in the composite,the quantify results were well fitted with si mulatiuon results.