Preparation And Properties Of Al₂O₃ Reinforced Graphite Brass

Graphite brass?Cu40Zn-Gr?is one of most promising substitute materials for lead brass because of its low cost and excellent machinability.In order to solve the contradiction between the mechanical properties and the cutting performance of Cu40Zn-Gr,alumina?Al₂O₃?nanoparticle was added to Cu40Zn-Gr.The lead-free and easy cutting brass with excellent comprehensive properties was prepared by the combination of Al₂O₃ and Gr particles with soft and hard coordination and the coordination of content.The composite powders of Cu40Zn-Gr,Cu40Zn-Al₂O₃ and Cu40Zn-Gr-Al₂O₃ were prepared by the combination of planetary ball milling and roller ball milling.The powder was cured by discharge plasma sintering?Spark plasma sintering,SPS?,and the density of the material was further improved by thermal extrusion?Hot Extrusion?.By analyzing the microstructure,density,hardness,mechanical properties and machinability of the materials,the effects of Gr and Al₂O₃ content on Cu40Zn and Al₂O₃ on the performance of Cu40Zn-Gr were studied,and the strengthening mechanism of the materials was systematically analyzed.The main conclusions are as follows:?1?According to the scanning electron microscope analysis of the mixed powder,the Gr and Al₂O₃ powder dispersed evenly after planetary ball milling 4h.Using 1:1 ball ratio,rotational speed 240r/min and roller mixed 1h ball milling process,Gr and Al₂O₃ powders are mixed with three powders of Cu40Zn powder,respectively.Gr is evenly distributed between Cu40Zn powder,and Al₂O₃ is evenly distributed on the surface of Cu40Zn powder.?2?According to the analysis of microstructure,mechanical properties and machinability of Cu40Zn-Gr after sintering,it is known that Gr evenly dispersed between Cu40Zn two phases.With the increase of Gr content,the hardness,yield strength,tensile strength and elongation of the specimen were decreasing,and there was a dimple and a large number of micro cracks at the fracture surface of the tensile specimen,Gr There was interfacial debonding between the Gr particles and the Cu40Zn matrix,and the tensile specimen is ductile fracture.The type of cutting chip was changed from spiral chip to short spiral and C type chip,and the cutting burr is less.The cutting effect and lubrication produced by adding Gr can obviously improve the cutting performance.?3?The microstructures,mechanical properties and machinability of Cu40Zn-Al₂O₃ treated after sintering were analyzed.The results showed that with the increase of Al₂O₃ content,the hardness and yield strength of the specimen were improved,while the tensile strength and elongation showed a downward trend.After the addition of Al₂O₃,the dimple of the tensile specimen is smaller and shallower,and the number of the fracture is reduced,and the broken surface of the fracture surface is distributed more Al₂O₃.The fracture was mode of the specimen is mainly plastic fracture.The cutting chips was mainly spiral chips,and the size of cutting chips gradually decreases with the increase of Al₂O₃ content.The stress concentration area formed around nanoscale Al₂O₃ can promote the breakage of cutting chips,and Al₂O₃ has a positive effect on the cutting performance of Cu40Zn.?4?Through the study of the mechanical properties and machinability of Cu40Zn-Gr-Al₂O₃after sintering.After adding Al₂O₃ nanopaticle,the yield strength of Cu40Zn-Gr was increased,while the tensile strength and elongation showed a downward trend,and the fracture mode of the material was mainly ductile fracture.The size of cutting chips decreased,and the C chips changed to short C type,detrital type and powder type.The addition of nano Al₂O₃ hinders dislocation migration and enhances yield strength of materials.The effect of Al₂O₃ on the cutting performance of brass reduced the required content of the Gr,reduced the adverse effect of Gr on brass and achieved the purpose of both mechanical and cutting properties.Cu40Zn-0.5Gr-0.5Al₂O₃ the material had the best performance,the yield strength of the material reaches 300MPa,the tensile strength is 450MPa,the elongation rate is 14.1%,and the most of the cutting chip is C type.