Influence Of Metal Impurity Doping On The Mechanical Property Of Alumina Dispersion Strengthened Copper Alloys

Dispersion strengthened copper alloys (DSC) with a wide range of applications in automobile and electronics industry combines the high strength with the high conductivity. It is of importance to understand fundamentally the interface chemistry and impurity segregation on Cu/Al2O3 interface to design and manufacture high performance nano phase dispersion strengthened copper alloys. The results of Cu/Al2O3 interface structure and adhesion strength calculated by first principle density function showed that the adhesion energy of Cu (111) and Al2O3 (0001) layer were 2.4~2.5 and 3.6~4.6 J/m2 compared to that of Cu or Al2O3, respectively. However, the adhesion strength of Cu/Al2O3 interface was low (0.7~0.8 J/m2), which is only one third of that of Cu. The weaker adhesion strength may be the major crack source. Cu-Al2O3 powder with various element doping was synthesized by high-energy ball milling under argon gas. The doping elements included Ag, Ni, Zr, Hf, and Ti that were assumed to prefer to segregate along Cu/Al2O3 interface. The influence of impurity doping on the mechanical and electrical properties of Cu-1.2wt%Al2O3 dispersion strengthened copper alloys was discussed. XRD results showed that the high-energy ball milling can dissolve Al2O3 and alloy elements into Cu matrix. As-milled powder was cold-pressed at 700Mp and then sintered at 860 oC, 900 oC, 940 oC and 980oC for 2.5h, respectively. Subsequently, sintered samples were cold-pressed again at 1200MPa to increase its density and the hardness was tested.Results showed that a certain amount of Ag doping can significantly improve the hardness of Cu alloys, while Zr doping slightly reduced it. In contrast, the improvement in hardness by doping Ni and Hf was clear but not that significant like Ag.From the results shown in SEM micrographs, it is found that a certain amount of Ag impurity can restrain the growth of alumina particles during sintering, which may lead to the reduction of alumina size, and increase the hardness of DSC at last. It can be sure that the decrease in Al2O3 size is closely related to segregation of Ag on Cu/Al2O3 interface that subsequently increases the adhesion strength of Cu/Al2O3 interface.