Study On Microstructure And Properties Of TiC Particle Reinforced Aluminium Bronze Composites By Selective Laser Melting

The aluminum bronze alloy plays a very important role in the mechanical industry,especially when the aluminum content is about 10%,it has good mechanical strength,wear resistance and resistance to seawater corrosion and cold resistance,so aluminum bronze is widely used in aerospace and marine engineering and other fields.However,the traditional cast aluminum bronze is prone to defects such as internal defects,holes and surface inclusions,and it is difficult to make parts with complex and fine structure.Moreover,the mechanical properties of metal parts change with the changes of microstructure including phase,grain size,shape,dendrite and element segregation.At present,optimizing microstructure is still a very important scientific challenge.Selective laser melting technology has been used to prepare high-performance structural parts with complex shape due to its advantages of rapid prototyping,improving raw material utilization,refining grains and realizing personalized design.To further enhance the hardness,strength,wear resistance and corrosion resistance of aluminum bronze materials can effectively enhance its application range.In this paper,using TiC particles and BrAl10Fe4 aluminum bronze powder as raw materials,the effects of laser power,scanning speed,powder thickness and scanning distance on microstructure,density,surface roughness,hardness and tensile strength of aluminum bronze forming parts were studied by orthogonal test and signal-to-noise ratio analysis.Secondly,the effects of the mass fraction of titanium carbide on the forming density,surface roughness and hardness of titanium carbide-aluminum bronze composites were investigated,and the enhancement of wear resistance and seawater corrosion resistance was studied by the addition of enhanced phase of titanium carbide particles.The high precision and high performance complex aluminum bronze parts and titanium carbide particles reinforced aluminum bronze composite complex parts were successfully prepared by laser selective melting process.The results show that t the optimal processing parameters are obtained by signal-to-noise ratio analysis: laser power 450 w?scanning speed 1700 mm/s?powder thickness 30?m,scanning distance 60?m.The microstructure of aluminum bronze parts printed under the optimal process parameters is white matrix ? phase andgray-black(?+?2)phase;the density of the parts reaches 98.94% of the theoretical density,the surface roughness is as low as 8.91 microns,and the average microhardness is 384.1 HV,which is far higher than that of traditional cast aluminum bronze(200 HV);the tensile strength of the aluminum bronze parts printed under the optimal process parameters reached 585 MPa,which was higher than that of the traditional cast aluminum bronze 490 MPa in the tensile test at room temperature.the fracture mode of the tensile parts was typical brittle fracture.clear river patterns and cleavage steps can be observed on the fracture surface.Printing titanium carbide particles reinforced aluminum bronze composite parts under optimum processing parameters,as the TiC mass fraction is 2.5%,5% and 7.5%,the density of the composite forming parts relative to the theoretical density is 97.93%,97.34%,96.8%,and the surface roughness also shows the tendency to increase first and decrease gradually,and its variation speed is first fast and then slow.Adding tic particles can effectively enhance the hardness of the forming parts,and when the TiC mass fraction is 5%,the microhardness of the composite is increased to 419 HV.When the content of the reinforcing phase is too low,the hardness of the forming part is not obvious,the surface roughness of the forming part is increased when the content is too high,and the spheroidization phenomenon is obvious.The addition of tic particles can effectively improve the wear resistance of slm forming parts.When the mass fraction of tic particles changed from 0% to 7.5% in dry friction and wear test at room temperature,the dynamic friction factor and wear amount of tic particle reinforced aluminum bronze composite decreased first and then increased,but all of them were lower than that of cast aluminum bronze.Adding tic did not obviously change the wear form of the forming parts,and the wear forms were all the result of plastic flow,accumulation,extrusion from the edge of the furrow under the action of load,and the joint action of slight adhesive wear and slight abrasive wear.At 2.5% and 5.0% of the enhanced phase content,the corrosion resistance of slm components was improved.an electrochemical corrosion test was carried out in the same corrosion solution(artificial seawater)with the highest polarization resistance and the widest passivation region at 2.5% tic content,followed by 5.0% titanium carbide content.When the content of titanium carbide increases again,the polarization resistance decreases,the corrosion rate of the composite increases,and the corrosion resistance to seawater decreases.when tic particles are not added,the forming parts are corroded obviously along the grain boundaries.at the TiC content of 2.5% and 5.0%,there were tiny white irregular spherical flocculentparticles on the surface of the sample,and the rest of the surface remained smooth,and no grain boundary corrosion was observed.as the content of the enhanced phase increases,the number of corrosion particles increases.although the presence of grain boundary corrosion is not observed,the corrosion products are dense.From the experiment,it can be seen that with the addition of a small amount of TiC,the distribution of each phase of the reinforced aluminum bronze forming parts by titanium carbide particles is more uniform,the effect of microbattery decreases relative to the non-reinforced phase,and the corrosion resistance of the forming parts increases.