Study On The Preparation Of SiC-Al₂O₃/2A50 Composite And Liquid Forging Forming Of Aluminum Alloy Wheels Locally Reinforced By Composite

Compared to traditional materials with a single texture,composites contain multiple components and possess higher strength–to–weight ratios,heat stability,higher fatigue strengths,and better fracture toughness.Inside,as a kind of composite with porous ceramics as reinforcement phases,ceramic–metal co-continuous composites are lightweight and possess a high wear resistance,high thermal shock resistance,and low thermal expansion coefficient.These properties enable the materials to withstand friction and high-temperature impact for at least a short period of time.Silicon carbide（SiC）,a lightweight ceramic with a density of3.17–3.47 g/cm³and a high hardness material with a Vickers hardness of 28 GPa,second only to diamond,can be used as the reinforcement phase in co–continuous composites.SiC ceramics also exhibit good thermal conductivity and oxidation resistance,and their mechanical properties remain stable at high temperatures.SiC ceramics can be combined with a lightweight aluminium alloy to form a composite material that can replace the traditional black metal.However,the application of ceramic–metal co-continuous composites remains limited to small engineering components.Research on the utilisation of ceramic–metal co–continuous composites in large engineering components is ongoing.In addition,SiC ceramics pose challenges with low wettability.In this study,considering practical engineering problems,SiC porous ceramics with a high–throughput topological structure were prepared using industrial-grade SiC abrasive particles and multicomponent mineral sintering additives.Subsequently,prefabricated parts of SiC/2A50 co-continuous composites were prepared using the SiC porous ceramics as the reinforcement phase and 2A50aluminium alloy as the metal matrix.Then,composited SiC–Al₂O₃porous ceramics were prepared by the surface modification of Al₂O₃on the SiC porous ceramics.Road wheels of 2A50 partly reinforced by the SiC–Al₂O₃/2A50 co-continuous composites were successfully fabricated as an alternative to wheels with traditional steel wear–resistant washers.Extrusion impregnation–liquid forging of the partly reinforced road wheels with the 2A50 aluminium alloy was realised.The prepared aluminium alloy wheel appeared complete,without macroscopic and microscopic defects.The metal matrix had a high tensile strength.Further,the composite parts maintained the characteristics of stable thermophysical properties and low wear rate,as well as stable connection with the road wheel.First,we examined a method in which industrial–grade SiC abrasive particles were used as ceramic aggregates instead of traditional SiC ceramic spherical particles.At first,Theoretical calculations of the sintering driving force were conducted based on the energy model to determine the experimental feasibility.For the synthesis of industrial–grade SiC abrasive particles,multi–component mineral sintering additives were specially designed and used with industrial-grade silica sol as a high–temperature binder,followed by liquid-phase sintering by doping the sintering aids,then the sintering of SiC abrasive particles was completed.The effects of the sintering temperatures on the component composition and lattice structure of the SiC preforms were studied using X-ray diffraction（XRD）.The compressive property of the SiC ceramic body was the highest at 1400℃when the compressive load reached 171.2 MPa.The sintering process of the SiC porous ceramics were determined via such analyses.Subsequently,SiC porous ceramics with high surface friction coefficients and desirable macro–and micro–-pore structuresweresuccessfullypreparedviaorganicfoam impregnation–high–temperature sintering.The compressive strength of the porous ceramics was then further analysed.The compressive strength of the SiC porous ceramics reached maxima of and 26.14 MPa,respectively.Meanwhile,the porosity of SiC porous ceramics reached 72.77%Finite element simulation and preparation experiments involving liquid forging to obtain prefabricated parts from the composites were carried out by ProCast.Thus,SiC/2A50 co–-continuous composite preforms were successfully prepared as the prepared SiC porous ceramic preforms were used as the reinforcing phase.Subsequently,we conducted T6 heat treatment experiments.Friction and wear as well as thermal expansion tests were conducted on the composite preforms at room temperature（≈25℃）and at a high temperature,respectively.The results revealed that the wear mechanisms of the composites varied under different friction and wear conditions.The composites showed the highest wear resistance and friction when the load was 50 N and the rotating speed of the friction disc was 0.8 m/s.The wear rate of the composite was 1.2×10^-4mm³/（N·min）,which was lower than that of38Cr Si steel(1.4×10^-4mm³/（N·min）).The SiC porous ceramics significantly decreased the thermal expansion coefficient and thermal expansion rate of the composites,and improved the thermal stability of the material.To address the problem of occasional incomplete infiltration in the SiC porous ceramics during infiltration experiments,the SiC porous ceramic were surface-modified using Al₂O₃particles,and composited SiC-Al₂O₃porous ceramics were prepared.And the comparison in the friction,wear,and thermophysical properties was studied.It was found that after surface modification of Al₂O₃,the infiltration effect of aluminum alloy melt on the SiC-Al₂O₃composited porous ceramics was better,improved the bonding strength of SiC/2A50 heterojunction interface,further improved the friction coefficient and thermal stability of the composite,and further reduced the wear rate.Thus,large composited SiC-Al₂O₃porous ceramic prefabricated rings with an outer diameter of 380 mm and an inner diameter of 340 mm were prepared successfully and were used as the reinforcing phase in integrated experiments involving the extrusion impregnation–liquid forging of aluminium alloy road wheels.After completion of the T6 heat treatment,the quality of the workpiece was evaluated in terms of the macroscopic morphology,microstructure,and mechanical properties.The results showed that the blanks with complete forms obtained through the integrated forming experiment met the required standard in terms of macroscopic dimensions,the microstructure of the aluminium alloy matrix was dense,and there were no macroscopic and microscopic defects.The microstructure of the aluminum alloy matrix was dense without macroscopic and microscopic defects,and the average tensile strength of the metal of the road wheel body was up to 428.4 MPa.Further study found that the structure of the composited SiC-Al₂O₃porous ceramic preform remained intact during the integrated forming experiment,with no breakage.The pores of the composited porous ceramics were filled,and no adverse interfacial reaction occurred at the heterogeneous interface.The composite parts in the wheels were well combined with the wheel,and had excellent friction-wear properties and stable thermophysical properties.