Study On The Microstructure,Properties And Preparation Process Of RGO/Cu-Zr-La Electrical Contact Material

The traditional low voltage electrical contact materials are mainly silver alloy materials,which not only expensive and easily depleted..Copper and copper alloy have excellent conductivity,thermal conductivity and ductility,so it is the preferred material to replace the silver based electric contact material.However,copper and copper alloys have low room temperature strength and poor corrosion resistance,which also restricts its wider application.In this paper,the copper alloy contact materials were prepared by repressing and re-sintering process process.The mechanism of copper alloy contact material of RGO and alloying elements Zr,La was studied;the effect of different addition amount of GO on the microstructure and properties of RGO/Cu-Zr-La contact materials were investigated,the effects of process parameters on the microstructure and properties of RGO/Cu-Zr-La contact materials were investigated by orthogonal test.So these main research results are as follows:The influences of the RGO,Zr and La elements on the microstructure and properties of RGO/Cu-Zr-La composites were investigated.The microstructure analysis showed that RGO and Zr existed in the grain boundaries,playing a role of pinning the grain boundaries movement.Due to fine grain strengthening and Orowan mechanism combined effect of dislocation,the hardness and strength of the RGO/Cu-Zr-La electric contact materials modified by GO,alloy element Zr and La are greatly improved.Compared with pure copper,the increase is 51.5% and 27.1%,respectively.The mechanical performances of RGO/Cu-Zr-La alloy increased evidently.The oxidation resistance of RGO/Cu-Zr-La alloy is improved.The more active rare earth element La is more likely to oxidize than the Cu atom to inhibit the diffusion of oxygen to the copper matrix and RGO platelets barrier action between oxygen and Cu matrix were main reasons.Secondly,the effects of the amount of GO(0.3wt.%,0.5wt.%,1.0wt.%,1.5wt.%)on the microstructure and properties of RGO/Cu-Zr-La composites were investigated.With the increase of the amount of GO,the relative density and electrical conductivity of the contact material gradually decreased.When the amount of GO addition is0.3wt.%,the maximum value is 99.42% and 90.8 IACS,respectively.Moreover,when the addition amount of GO is too high,the RGO is easily aggregated at the grain boundary,and the bonding strength between copper grains decreases,which reduces the densification of the material and makes the hardness of the material decrease.Themicrohardness of the 0.5wt.% RGO/Cu-Zr-La composites is the highest,which is 92.1HV.When GO content is small,it forms a good interface bonding with copper matrix,so that load can be effectively transferred from copper matrix to high strength RGO,and the strength of copper composite material is improved.1.5wt.% RGO/Cu-Zr-La compared to 0.3wt.% RGO/Cu-Zr-La,the elongation decreased by 60.7%,while the tensile strength of the 0.5 wt.% RGO/Cu-Zr-La is the largest,which is 229.1 MPa.Finally,the orthogonal test was used to optimize the preparation process parameters of the 0.5wt.% RGO/Cu-Zr-La electric contact material.The results show that the recompacting pressure on the relative density of RGO/Cu-Zr-La contact materials is the most significant impact,so is a key factor in the preparation of excellent properties of materials.Pre-sintering temperature effect on the conductivity of RGO/Cu-Zr-La contact materials is very significant,so the selection of Pre-sintering temperature is the main factor affecting the conductivity of composites.Resintering temperature is mainly to eliminate work hardeningand homogenization of the material.The suitable re-compaction pressure can make the powder compacted and increase the degree of alloying after first sintering.After analyzing the effect of various factors on the properties of RGO/Cu-Zr-La contact materials,the best preparation process parameters of 0.5 wt.% RGO/Cu-Zr-La electrical contact material were obtained as re-compaction pressure of 400 MPa,pre-sintering temperature of 1000 ?,recompacting pressure of 1000 MPa,and resintering temperture of 850 ?.Compared with the 0.5wt.% RGO/Cu-Zr-La composites prepared by the conventional process,the tensile strength and elongation of the composites prepared by the optimum process were239.3 MPa and 26.4%,which increased by 4.5% and 42.7% respectively.