烧结工艺对CuSnZn合金粉末性能的影响

Effect of sintering process on properties of CuSnZn alloy powder

提高金刚石工具的性能并控制其生产成本已成为工程应用领域的重点研究方向。本研究中,通过雾化法制备不同Zn质量分数(10.00%~30.00%)的CuSnZn合金粉末,在610~655℃不同的热压烧结温度和21 MPa的烧结压力下制备烧结节块,并对烧结节块的理论密度、洛氏硬度、抗弯强度、显微形貌进行分析。结果表明:随着Zn含量升高,CuSnZn合金粉末熔化温度逐渐降低,当Zn质量分数为30.00%时,熔化温度降低到848℃;当Zn质量分数为20.00%时,烧结节块致密度降低至97.6%;烧结节块的抗弯强度先升高后降低,当Zn质量分数为20.00%时,达到最大值542 MPa;烧结节块中的黄铜由α相逐渐转变为α+β相和α+β+β′相,其洛氏硬度显著提升;节块的断裂方式由沿晶断裂逐渐过渡到穿晶断裂。

Objectives:Diamond tools are crucial in stone processing,and their performance is directly related to pro-cessing quality and cost.With the rise of stone and labor costs,the performance requirements on diamond tools are also increasing,including sharpness,self sharpening,tool life,and cutting efficiency.To improve efficiency and reduce costs,users often increase the cutting machine power and speed,which further requires diamond tools to have higher sharpness and strength at the risk of breakage.A practical method method is to increase the content of tin(Sn)in the segment to enhance its brittleness without changing the diamond concentration and particle size.However,an increase in Sn content will reduce the strength of the segment and may lead to a decrease in the holding force between CuSn al-loy and diamond.For example,the commonly used CuSn10 and CuSn15 pre alloy powders in industry have low strength and weak holding force on diamond.Therefore,it is necessary to improve the powder properties and pro-cessing technology.Methods:Adding Zn element to CuSn10 alloy powder can improve powder strength and holding force.CuSnZn-x alloy powder(mass fraction of Zn,x=10.00%,15.00%,20.00%,25.00%,30.00%)was prepared by at-omization process.The hot pressing sintering temperatures were 610℃,615℃,630℃,645℃,655℃,and the sinter-ing pressure was 21 MPa.The melting temperature of CuSnZn alloy powder was tested using a differential thermal ana-lyzer.The density of the sintered segment was tested using Archimedes drainage method.The bending strength of the sintered segment was tested using mechanical performance testing equipment.The Rockwell hardness of the sintered segment was measured using a Rockwell hardness tester.The microstructure morphology of the sintered segment and its fracture were analyzed using scanning electron microscopy.Other performances of samples with different Zn contents were analyzed and compared as well,namely theoretical density,Rockwell hardness,and flexural strength,to study the influence of Zn content on sample microstructure.Results:With the increase of Zn content,the rate of decrease in melt-ing temperature of CuSnZn alloy powder first increases and then decreases.When the Zn mass fraction is 30%,the melt-ing temperature decreases to 848℃,which is 164℃lower than that of CuSn10.As the Zn content increases,the brass in the sintered segment gradually transforms from theαphase to theα+βphase and then theα+β+β´phase,resulting in a significant increase in the Rockwell hardness of the segment.The bending strength of the sintered segment first in-creases and then decreases,reaching a maximum value of 542 MPa when the Zn mass fraction is 20.00%.When the mass fraction of Zn is 10.00%and 15.00%,obvious toughness dimples are observed on the fracture surface of the sintered segment,and particle peeling is observed on the fracture surface.The peeling surface is smooth and flat,indic-ating grain boundary peeling fracture of the phase structure.When the mass fraction of Zn is 20.00%and 25.00%,a large number of cleavage fracture surfaces are observed on the fracture surface of the sintered segment,and a small amount of smooth concave transgranular fracture is observed,which is partially intergranular fracture and partially transgranular fracture.When the mass fraction of Zn is 30.00%,the fracture surface of the sintered segment is flat and smooth,and the crack passes through the phase interface and grain along the hard and brittle structure,which is trans-granular fracture.Conclusions:Adding Zn element can effectively reduce the melting point of alloy powder,and with the increase of Zn content,the hardness of sintered samples increases while the toughness decreases.When the Zn con-tent is 30.00%,the melting temperature of CuSnZn alloy powder reaches its minimum value.When the Zn content ex-ceeds 25.00%,the strength of the sintered samples will gradually decrease.Therefore,in actual production,the appropri-ate amount of Zn addition and sintering process should be selected based on comprehensive consideration of demand.