| Due to its excellent conductive and thermal conductivity,good corrosion resistance and ductility,copper and copper alloys become irreplaceable metal materials in routine life and industrial production.However,low Strength and hardness and poor wear resistance under normal temperature and high temperature hampered the further development and utilization of copper material.In order to meet higher requirements on copper and copper alloys put forward by the rapid development of industry,researchers have developed many new methods to reinforce copper and copper alloys.In these methods,adding the ceramic particles into copper matrix can not only improve the mechanical properties,but also reduce the decline of conductive and thermal conductivity of copper matrix.According to current research,most of ceramic particles added to the copper matrix are micron-sized.While,the results of study on Al and Mg matrix composites indicate that smaller size ceramic particles can reinforce the metal matrix more effectively.Therefore,the research of nanometer size ceramic particles reinforced copper matrix composites is necessary.There are two ways to introduce ceramic particles into metal matrix: interior addition and in situ method.Compared with the traditional interior addition way,in situ method not only can generate smaller sized ceramic particles with uniform distribution,also reduce the surface pollution of ceramic particles,improve the interface bonding strength of the reinforcing particles and copper matrix.In situ method has become the preferred method for preparing nano-sized particles reinforced copper matrix composites.In this article,we prepared in situ nano Ti C_x/Cu composites in Cu-Ti-C reaction system by combustion synthesis and hot press technology.We explored the effect of Ti C_x content and C/Ti molar ratio on Ti C_x particles size and morphology,microstructure,room temperature compression performance and conductivity.We also explored the Ti C_x content and C/Ti molar ratio on the wear performance of the Ti C_x/Cu composites at room temperature.At the same time,high temperature wear mechanism of 30 vol.% Ti C_x/Cu composites also be discussed by changing temperature and load during wear process.The main conclusions of this article are:(1)It found that with the increase of Ti C_x content,the Ti C_x particle size increases significantly,While the yield strength and maximum compression strength of the Ti C_x/Cu composites first increase and then decrease,and fracture strain shows an opposite trend.The 30 vol.% Ti C_x/Cu composites shows the best compression performance,its yield strength,maximum compression strength and the fracture strain are 495 MPa,969MPa and 6.88%,respectively.Nano Ti C_x particles dispersed in Cu matrix can reinforce Cu matrix by inhibit the dislocation motion.However,The increase of the Ti C_x particle size weak their strengthening effect.Which led to decrease in compression performance of the Ti C_x/Cu composites.At the same time,With the Ti C_x content increases from 25 vol.% to 35 vol.%,the conductivity of the Ti C_x/Cu composites decreases from 48%IACS to 40%IACS.(2)It found that with the increase of C/Ti molar ratio,the Ti C_x particle size displays little variation,the yield strength and maximum compression strength of the 30 vol.%Ti C_x/Cu composites decrease and fracture strain increase.It is mainly due to the increase of Ti C_x particles' metallicity result from the increase of C/Ti molar ratio,which could enhance wettability and interfacial bonding strength between Ti C_x particles and Cu matrix.And the remaining Ti atoms will solve into the Cu matrix,it also can significantly reinforce Cu matrix.When C/Ti molar ratio is 0.4,the 30 vol.% Ti C_x/Cu composites shows the best compression performance,its yield strength,maximum compression strength and the fracture strain are 1110 MPa,1288MPa and4.91%,respectively.At the same time,With the C/Ti molar ratio increases from 0.4 to 1.2,the conductivity of the 30 vol.%Ti C_x/Cu composites increases from 18%IACS to 49%IACS.(3)It found that volume wear rate of Ti C_x/Cu composites first increase and then decrease with the increase of Ti C_x content.The wear resistance is best when Ti C_x content is 30 vol.%.The changes of wear resistance have consistent with hardness change of Ti C_x/Cu composites.(4)It found that volume wear rate of 30 vol.%Ti C_x/Cu composites increase with the increase of C/T molar ratio.The wear resistance of 30 vol.%Ti C_x/Cu composites is best when C/T molar ratio is 0.4.Although Ti C_x content remain unchanged in this pair of experiment,the increase of C/T molar ratio reduces the number of Ti atoms solved in Cu matrix,which will decrease the hardness and wear resistance of 30 vol.%TiC_x/Cu composites.(5)It reveals the effect of nano-sized Ti C_x particles on the high temperature wear performance of 30 vol.% Ti C_x/Cu composites.?)It found that the volume wear rate of Ti C_x/Cu composites and pure Cu are both first decrease and then increase,but the volume wear rate of Ti C_x/Cu composites has been consistently lower than pure Cu.It is due to high temperature stability of Ti C_x particles,which can still reinforce the Cu matrix under high temperature.The volume wear rate of Ti C_x/Cu composites is lowest under 180?,it is because that compared with room temperature,high temperature can promote formation of oxidation film on wear surface.This oxidation film will protect the wear surface to reduce the volume wear rate of 30 vol.%Ti C_x/Cu composites.When the wear temperature is 220?,30 vol.%Ti C_x/Cu composite exhibits certain softening,the composite unable to support the MML on its surface,then plurality of flake layer spalling from wear surface,the volume wear rate increases significantly.?)It reveals high temperature wear mechanism of 30 vol.%Ti C_x/Cu composite in this experiment conditions.When the wear temperature is below 180?,the wear modes mainly include abrasive wear,slight adhesive wear and oxidation wear.When the wear temperature is above 180?,the wear modes mainly include exfoliative wear,oxidation wear and abrasive wear.?)It found that the volume wear rate of Ti C_x/Cu composites increases with the increasing wear load at 220?.With the increase of wear load,the depth of raised points on grinding pan press into the wear surface is also increases,which will reduce the wear resistance of 30 vol.%Ti C_x/Cu composite.At the temperature of 220?,the critical load of 30 vol.%Ti C_x/Cu composite and pure Cu are 30 N and 20 N,respectively.This illustrates that nano-sized Ti C_x particles can resist the soften of Cu matrix at high temperature,then remarkably increase the wear resistance of composites. |
PDF Full Text Request