电脉冲处理对黄铜组织性能影响及机理研究

发布时间：2018-06-01 20:02

  本文选题：无铅黄铜 + 电脉冲处理　； 参考：《北京科技大学》2015年博士论文

【摘要】：本文利用电脉冲熔体处理和变质处理技术对铅黄铜铸态组织、铸造性能及切削性能的影响进行对比研究,确定电脉冲熔体处理可以有效细化铅黄铜微观组织结构,进而改善其切削性能。在此研究基础上,以电脉冲熔体处理技术为强化手段,以硅代替铅并结合有效合金化理论和适当的热处理工艺探索一种具有易切削、耐磨耐蚀性能的(β+γ)双相硅黄铜合金。通过对该合金液固转变和固态相变特点的研究,建立了(p+γ)双相硅黄铜合金熔体中电脉冲“孕育”团簇的机理模型,并在实验上验证了模型的准确性。 研究结果表明,适当参数的电脉冲作用于(β+γ)双相硅黄铜合金熔体能够细化其凝固组织,增加Si在p相基体中的固溶度,减少合金凝固组织中丫相的尺寸和数量,改善合金中γ相的偏析程度,进而提高了该合金的切削、耐磨及耐蚀性能。当脉冲电压为1000V,处理时间为30s,脉冲频率为8Hz时,合金凝固组织中γ相呈点状均匀弥散分布于p相基体中,γ相尺寸由44μm减小到22μm,γ相体积份数由66.23%减少到49.94%,基体显微硬度由336.03HV升高到399.62HV,抗拉强度由250MPa提升至380MPa。 电脉冲处理后(β+γ)双相硅黄铜合金熔体结构模型认为,电脉冲熔体处理增强了合金熔体中游离的Zn原子与富Cu的Cu-Zn原子团簇间的作用,增加了合金熔体中富Cu的Cu-Zn原子团簇数量,且该原子团簇尺度向小尺度方向发展。通过综合热分析、热膨胀分析、丫相尺寸及其体积份数的变化、基体显微硬度等实验对该模型的正确性进行间接地验证。同时,以此模型为基础,分析了电脉冲处理细化(β+γ)双相硅黄铜合金凝固组织、改善合金偏析、提高合金耐磨和耐蚀性能的作用机制。 在(β+γ)双相硅黄铜合金电脉冲熔体处理工艺研究的基础上,对其热处理工艺进行研究,为电脉冲熔体处理技术的实际应用奠定坚实的试验基础。研究表明：在经过最佳脉冲处理参数(脉冲电压为1000V,处理时间为30s,脉冲频率为8Hz)处理后的(β+γ)双相硅黄铜合金再经600℃、4h固溶、水淬,250℃、6h人工时效后,合金的基体显微硬度仅为未处理时的75%。采用此热处理工艺既能消除电脉冲细晶及β相固溶强化所导致的基体硬度升高,同时亦可实现对γ相的有效变质,提高其切削性能,为无铅易切削硅黄铜的新技术开发提供理论基础。
[Abstract]:In this paper, the effects of electropulse melt treatment and modification on the cast structure, casting properties and cutting properties of lead brass were compared and studied. It was determined that the electric pulse melt treatment could refine the microstructure of lead brass effectively. Then the cutting performance is improved. On the basis of this study, a kind of (尾 纬) duplex silicon brass alloy with easy cutting and wear resistance and corrosion resistance was explored by means of electric pulse melt treatment technology, silicon instead of lead and effective alloying theory and proper heat treatment technology. Based on the study of the liquid-solid and solid phase transition characteristics of the alloy, the mechanism model of electric pulse "inoculation" in the melt of p 纬) silicon brass alloy has been established, and the accuracy of the model has been verified experimentally. The results show that the effect of electrical pulse with appropriate parameters on the solidification structure of (尾 纬) two-phase silicon brass alloy can refine the solidification structure, increase the solid solubility of Si in p-phase matrix, and reduce the size and quantity of Ya phase in solidified microstructure of the alloy. The segregation degree of 纬 phase in the alloy was improved, and the cutting, wear resistance and corrosion resistance of the alloy were improved. When the pulse voltage is 1000V, the processing time is 30s and the pulse frequency is 8Hz, The 纬 phase in solidified microstructure is distributed uniformly in p phase matrix, the size of 纬 phase decreases from 44 渭 m to 22 渭 m, the volume fraction of 纬 phase decreases from 66.23% to 49.94, the microhardness of matrix increases from 336.03HV to 399.62 HVand the tensile strength increases from 250MPa to 380 MPA. The (尾 纬) dual phase silicon brass alloy melt structure model shows that the electric pulse melt treatment enhances the interaction between the free Zn atom in the alloy melt and the Cu rich Cu-Zn cluster. The number of Cu rich Cu-Zn cluster in the alloy melt was increased and the scale of the cluster developed to a small scale. The correctness of the model was indirectly verified by comprehensive thermal analysis, thermal expansion analysis, changes of phase size and volume fraction, and matrix microhardness. At the same time, based on the model, the mechanism of electric pulse treatment for refining (尾 纬) double phase silicon brass alloy solidified microstructure, improving alloy segregation, improving the wear resistance and corrosion resistance of the alloy was analyzed. Based on the study of (尾 纬) duplex silicon brass alloy electric pulse melt treatment technology, the heat treatment process is studied, which lays a solid experimental foundation for the practical application of electric pulse melt treatment technology. The results show that after the best pulse treatment parameters (pulse voltage 1000V, treatment time 30s, pulse frequency 8Hz), the (尾 纬) dual phase silicon brass alloy is dissolved at 600 鈩，

本文编号：1965448