Study On Fabrication And Properties Of Ti₃SiC₂ Dispersion Strengthened Copper Composites

Graphite dispersion strengthened copper is a kind of electrofriction material widely. It is used as pantograph slide plates for electromotive because of its good electrical conductivity, heat conductivity and good self-lubricating property as the incorporation of graphite. But its tensile strength and dynamic ductility are not so good because the graphite is flexible and the great difference of the coefficient of thermal expansion between graphite and copper.Ti₃SiC₂ is a new ceramic and is now become a focus of research because it both has the properties of ceramic and metal material. The electrical conductivity under room temperature of Ti₃SiC₂ is 9.6×10^-6Ω^-1·m^-1 which is much more high than graphite. Its heat conductivity in the range of 25¹000℃ is (10—11) ×10^-6℃^-1 which is close to that of copper, that is 17×10^-6℃^-1. The compression strength is 900MPa, the Young's module and hardness is 326GPa and 4GPa separately. Otherwise, the oxidation resistance under 1300℃ is much higher than that of graphite. So Ti₃SiC₂ is considered to be the best replacement of graphite.In this paper, we successfully fabricated Ti₃SiC₂ dispersion strengthened copper composite—Ti₃SiC₂ with Cu powder and Ti₃SiC₂ powder by hot pressing. We concluded the best filler content is 15vol% by variated the filler content from 5vol% to 30vol% with 5vol% percentage increase. By comparing the properties of the samples prepared under different conditions, we conclude the best processing parameter is 900°C, the pressure is 30MPa, sintering holding time is 2 hour. The experiment result demonstrated that with the increase of the Ti₃SiC₂ content, the relative density of the composite decrease. The longer the sintering holding time is, the lower the relative density is, the reason is that the crystal grain becomes bigger under the long sintering holding time. The electrical resistance of Cu/Ti₃SiC₂ composite is also lower as the longer of the sintering holding time. From the result, we know that only the composite's softening temperature is below 900℃, which with filler content of 5vol%. By comparison, the friction coefficient of Cu/Ti₃SiC₂ and Cu/graphite composites is equivalence. But the mechanical properties of Cu/Ti3SiC2 are better than that of Cu/graphite, such as compression strength and brinell hardness.Cu/Ti₃SiC₂ composite was also fabricated with Cu powder and electroless copper plated Ti₃SiC₂ powder, we compared with Cu/Ti₃SiC₂ composite fabricated with Cu powder and Ti₃SiC₂ powder. It can be found from the microstructure and fracture thatthe filler was uniform distributed in the copper matrix, which demonstrated that the wettability of Cu and Ti3SiC2 was improved after the electroless copper plating. The relative density was also improved because of the uniform microstrucrure. As the increase of the density, the electric conductivity and mechanical properties were also increased. The trend of relative density and brinell hardness was almost the same of the two composites. With the same filler content, the relative density of composite with copper coated Ti3SiC2 is higher than that with uncoated Ti3SiC2. As the filler content above 15vol%, the density of Cu/Ti3SiC2 with uncoated Ti3SiC2 powder decreased much more rapidly than composite with copper coated Ti3SiC2powder. Both the two composites had a max of hardness with 20vol% filler content, the max are 108.4HBS for copper coated and 105HBS for uncoated. When the filler content is the same, composite with the copper coated T13S1C2 had a higher hardness than composite with uncoated Ti3SiC2- The max of tensile strength for Cu/Ti3SiC2 composite with copper coated Ti3SiC2 is 312.4MPa, while the tensile strength for Cu/Ti3SiC2 composite with uncoated Ti3SiC2 is 268.8MPa, which decreased when the filler content above 10vol%. The tensile yield strength was enhanced from 21602MPa for Cu/ Ti3SiC2 composite with uncoated Ti3SiC2 to 247.1MPa for Cu/Ti3SiC2 composite with copper coated Ti3SiC2.