摘要
CuCr合金是真空高压开关领域最佳的触头材料之一。为了研究CuCr(50)合金整体的偏析情况,采用铝热还原制备CuCr(50)合金,将外加磁场技术应用于CuCr(50)合金熔体的凝固过程,研究外加电磁搅拌的条件下铝热还原制备的CuCr(50)合金整体的微观组织、致密度、电导率以及硬度的影响;之后采用固溶以及时效的热处理工艺处理铝热还原所制备的CuCr(50)合金,观察其微观组织和性能变化。结果表明:运用外加磁场技术后铝热还原制备的CuCr(50)合金熔体能有效地克服高Cr含量的CuCr(50)合金的易分层现象,Cr相均匀分布在Cu基体中,从而有效地解决CuCr(50)合金的偏析问题,实现CuCr(50)合金的均质化,同时合金的密度达到国标要求的7.9 g·cm^(-3),实现合金的致密化,合金的硬度也达到国标要求的HB 80,但电导率略低于国标的16 MS·m^(-1);而之后热处理工艺能够细化CuCr(50)合金中Cr相组织,降低Cu中固溶的Cr相,从而合金的电导率从从11.09 MS·m^(-1)增加至14.9 MS·m^(-1),提高了34.4%,合金的硬度由HB 87.9增加至HB 95.2。
CuCr alloy is one of the best contact materials in the field of vacuum high-voltage switches,and the densification and homogenization of CuCr(50) with high Cr contents are a major problem that restrict the development of CuCr alloys.Thermite reduction,whose routes and steps are gradually mature,has become a new process for preparing CuCr alloys.Therefore,the external magnetic field process was applied to study the dense and homogeneous of CuCr(50) alloy prepared by thermite reduction in one step,and the properties of the alloy were analyzed and improved.Copper oxide CuO and chromium oxide Cr2O3were used as raw materials,Al powder was used as a reducing agent,KClO3was added as a heating agent,and CaO was used as a slagging agent,a fully miscible CuCr melt was quickly obtained through the reduction reaction,which solved the problem of serious macro-segregation caused by the traditional smelting process due to the obvious temperature gradient field of the heating rate.During the solidification of CuCr(50) alloy,the rotating magnetic field was applied to provide electromagnetic stirring,which overcame the delamination caused by the different density of Cu and Cr,and improved the homogeneity of the alloy.The electromagnetic stirring relied on the high-speed rotation of a magnet to form a spiral magnetic field to act on the molten metal.CuCr(50) alloy,divided into 3 parts with 20 mm as a unit,with a height of 60mm prepared by aluminothermic reduction under an external magnetic field had Cu content of 49.00%and Cr content of47.70%in the upper part of the alloy;Cu content of 49.90%and Cr content of 48.30%in the middle part;Cu content of 50.40%and Cr content of 47.60%in the lower part.The composition of the upper,middle,and lower parts of the alloy was evenly distributed,with no macro-segregation phenomenon existed in CuCr(50) alloy as a whole,the composition of CuCr(50) alloy could meet the national standards of CuCr(50) alloy.Copper-rich phases,chromium-rich phases and inclusion phases were existed in the microstructure of CuCr(50) alloys,the Cr-rich phases were existed in the form of granules and strips,Cr phase structure was evenly distributed in Cu phase,with no obvious micro-segregation and coarse Cr crystals.The contents of solid solution Cr in Cu in each part were higher than0.7%of the maximum solid solubility of Cr in Cu in the binary phase diagram,which showed supersaturated solid solution Cr atoms were existed in the Cu matrix.The inclusion phases included Al2O3inclusions and composite inclusions of Al2O3and Cr2O3.The density of CuCr(50) alloy prepared by the aluminothermic reduction under the external magnetic field could reach 7.96 g·cm^(-3),the relative density reached 97.88%,the electrical conductivity of different parts of the alloy as a whole was in the range of 11.71~12.49 MS·m^(-1),and the hardness was in the range of HB 85~HB 95,which verified the homogeneity of the alloy,the density and hardness of the alloy could meet national standards,but the conductivity was lower than the national standard 16 MS·m^(-1).Through the heat treatment process of solution temperature 950℃+solid solution time 80 min of solution treatment and aging temperature 500℃+aging time 4 h of aging treatment,the amount of small grain size Cr phase structure increased,and Cr phase was obviously refined,the amount of elongated Cr phase structure was reduced,the amount of spheroidal Cr phase structure increased,the solid solution Cr phase in Cu was reduced to about 0.7%,and the supersaturated Cr atoms in Cu matrix disappeared.The electrical conductivity of the alloy increased from11.09 to 14.9 MS·m^(-1),an increase of 34.4%,and the hardness was also increased from HB 87.9 to HB 95.2.The thermite reduction process under the external magnetic field overcame the two-phase delamination phenomenon that was easy to appear in the solidification process of the high Cr contents CuCr(50) alloy,and solved the macro segregation of the alloy.At the same time,Cr phase was uniformly distributed in Cu matrix to realize the homogenization of CuCr alloy.The density of the alloy was higher than the national standard of 7.9 g·cm^(-3),which realized the densification of CuCr alloy.The heat treatment process could reduce the supersaturated Cr atoms in Cu matrix,so the electrical conductivity of CuCr(50) alloy could be improved.In addition,Cr phase structure was significantly refined,and Cr could be dispersed and precipitated from the solid solution with nano-sized particles,and the fine Cr particles played a role of the dispersion strengthening,the hardness of CuCr(50) alloy could be further improved.Therefore,through the external magnetic field process and heat treatment,the homogeneous and compact CuCr(50) alloy,which met the performance requirements,could be prepared through thermite reduction in one step.
作者
韩金儒
豆志河
张廷安
安旺
Han Jinru;Dou Zhihe;Zhang Ting'an;An Wang(School of Metallurgy,Northeastern University,Shenyang 110819,China)
出处
《稀有金属》
EI
CAS
CSCD
北大核心
2023年第2期193-202,共10页
Chinese Journal of Rare Metals
基金
国家自然科学基金项目(51774078,U1908225)
中央高校基本科研业务费(N182515007,N170908001)资助。
关键词
CUCR合金
外加磁场
铝热还原
均质性
致密性
CuCr alloy
applied magnetic field
thermite reduction
homogeneous
densification
