Research On Fabrication And Mechanical Properties Of Nanometer SiC_p Reinforced Zn-Al Matrix Composites By Compound Stirring Casting Technique

Particle reinforced Zinc-Aluminum matrix composite become a new generation of light alloy material that in place of copper alloy bearing and in response to automotive lightweight development.However,its mechanical and wear resistance properties that reduced acutely and unstable under the friction condition of heavy load and high speed as well as preparation process,which limits its large-scale application.At the same time,the infiltration and dispersion of nanometer reinforcement and its influence mechanism on mechanical and wear resistance properties of particle reinforced Zinc-Aluminum matrix composite that reduced acutely and unstable under the friction condition of heavy load and high speed are not clear.Therefore,this article based on the advantages of ball mill mixing,powder of high pressure spraying,mechanical stirring,melt ultrasonic treatment and rapid solidification techniques.So that established the process system of compound stirring casting technique on the preparation of nano SiC_p reinforced Zinc-Aluminum matrix composite,and optimized the experimental parameter on the process system of compound stirring casting technique by the BP neural network.The change rules on the micro structure,mechanical properties and friction and wear performance of nano SiC_p reinforced Zinc-Aluminum matrix composite during the different contents of nano SiC_p and the different conditions of super gravity solidification and stabilization technology was studied.Combined with structural characteristics of the interface between reinforcement and matrix of the composite materials,the strengthening mechanism of nano SiC_p on the mechanical properties and the friction and wear properties of composite materials at heavy load and high speed was revealed under the conditions of super-gravity solidification and stabilization.The main research conclusions are as follows:?1?To establish the compound stirring casting process system that jointed the high pressure spray powder,mechanical stirring,ultrasonic melt,rapid solidification.And determined the composition of Al is 38 wt%,Cu is 3.5 wt%,the Mg is 1.2 wt%,during the melt temperature is 750°C,the stirring speed is 800 rpm,the melt ultrasonic power is750 w?watt?,that nanoSiC_p/Zn-38Al-3.5Cu-1.2Mg composite materials could be successfully prepared with better mechanical and wear resistance properties,and the reinforcement in the composite better evenly dispersed.?2?The 0.20wt%contents nanoSiC_p/Zn-38Al-3.5Cu-1.2Mg composite had the best performance,with the compressive strength and fracture strain were 765 MPa and12.96%,tensile strength and elongation were 421.49 MPa and 5.16%,respectively.The dry friction and wear rate is 2.75×10^-2mm³/m that decreased 35%better than matrix with4.23×10^-22 mm³/m.The temperature of friction wear surface on 0.50wt%nano SiC_p composites is 216°C during 8.79 m/s and 0.84 MPa,while matrix is 120°C.Friction lead to the plastic deformation and fracture of contact surface,and the friction surface gradually changes from plough mark and adhesive layer to adhesive layer.The main wear mechanism is adhesive wear.The fracture characteristics of the composites are both ductile fracture and brittle fracture,and the fracture originates from the cleavage fracture caused by nano SiC_p agglomeration and its brittleness during the solidification process and the interface separation between matrix and reinforcement within the composites.?3?The dispersion of nano SiC_p was improved by super gravity solidification technique,and the gradient distribution of the properties of composite materials was caused.With the increase of the super gravity acceleration during solidification,the mechanical and wear resistance properties increased.The compression performance and wear resistance in the 6000 g acceleration of super gravity solidified composite were the best at room temperature.The compression strength and fracture strain were 738 MPa and 27.16%,respectively.The dry friction wear rate was 1.033×10^-22 mm³/m during the conditions of heavy load and high speed of 1.41 MPa and 11.72 m/s,which was about183%higher than that of the matrix,and the main wear mechanism was adhesive wear,but fracture is the result of the mixing of shear and cleavage fracture.?4?The 380°C×6 h+170°C×48 h stabilizer process is the best that the nano SiC_p distribution of composite material is more uniform.The compression strength and fracture strain of the treated composite are 956 MPa and 16.82%,respectively,which are24.98%and 29.78%higher than those of untreated composite,and the dry friction wear rate was 1.43×10^-22 mm³/m during the conditions of heavy load and high speed of 1.41MPa and 11.72 m/s.Its micro hardness increased with the increase of friction temperature,and fracture characteristics are the result of ductile and brittle fracture.The change of matrix micro structure and nano SiC_p distribution caused by the stabilized composite can hold back the wear resistant phase structure transformation in friction and wear process under heavy load and high speed conditions.?5?At different nano SiC_p content and different super gravity solidification,there was no obvious change in the reinforcement-matrix interface of the composites,while the interface of the composites after stabilization treatment had obviously change.The grain boundary are connected to form by??Al,Zn?,??Al,Zn?and??Cu,Zn?,SiC_p gathered in both internal and edge grain boundary of?and?,where?is less.MgAl₂O₄ is the interface bridge effect between SiC_p and?grain boundary.The reinforcement mechanism of nano SiC_p reinforced Zinc-Aluminum matrix composite,which measured enhancement of Orowan strengthening mechanism is 115.56 MPa>thermal mismatch strengthening reinforced measure at 74.28 MPa>fine grain strengthening reinforced at38.14 MPa>directly load transfer of the improved.