冷却方式对超因瓦合金热膨胀与软磁性能的影响研究

Effects of cooling methods on thermal expansion and soft magnetic properties of super-invar alloys

关键词:  FeNi32Co5合金  冷却方式  低膨胀性能  软磁性能  热处理

Key words:  FeNi32Co5 alloy  Cooling methods  Low expansion properties  Soft magnetic properties  Heat treatment

摘要:

通过金相显微镜、X射线衍射分析、热膨胀性能测试和软磁性能测试等方法，研究了850 ℃均匀化退火后炉冷（FC）、空冷（AC）、水冷淬火（WQ）和液氮淬火（LNQ）四种冷却方式对FeNi32Co5合金的显微组织、热膨胀和软磁性能的影响，同时进一步分析了回火处理对合金综合性能的影响。结果表明，OS，FC，AC和WQ试样主要为面心立方（fcc）奥氏体相，同时含有少量的体心立方（bcc）相，LNQ试样出现大量bcc马氏体相，退火后各试样晶粒均发生粗化；WQ试样在20~100℃的平均线膨胀系数α(20~100 ℃)仅为0.38×10-6·K-1，较原始OS试样降低了56.32%，并且最大磁导率μm提升至1.908 k，矫顽力Hc降低至91.32 A/m；对WQ试样进行315 ℃回火处理（WQ-TP）后有效改善了由热应力导致的软磁性能损伤，WQ-TP试样的最大磁导率μm进一步提升至2.993 k，矫顽力Hc降低至57.8 A/m，同时保持了优异的低膨胀性能（α(20~100 ℃) = 0.54×10-6·K-1）。综合考虑下，对均匀化退火后的合金进行水冷淬火和回火处理可获得兼具优异的软磁性能和低膨胀性能的FeNi32Co5合金。

Abstract:

The effects of furnace cooling(FC), air cooling(AC), water cooling quenching(WQ) and liquid nitrogen quenching(LNQ) on the microstructure, thermal expansion and soft magnetic properties of FeNi32Co5 alloy after homogenization annealing at 850 ℃ are investigated by metallographic microscopy, X-ray diffraction analysis, thermal expansion property test and soft magnetic property test, and the effects of tempering treatment on the comprehensive properties are also further analyzed. The results show that the OS, FC, AC and WQ specimens are mainly consisted of fcc austenite phrase with a small amount of bcc phase, while the LNQ specimens show a large amount of bcc martensitic phase, and the grains of each specimen are coarsened after annealing. The average linear expansion coefficient α(20~100 ℃) of the WQ specimens is 0.38×10-6·K-1 at 20~100 ℃, which improves the thermal expansion performance by 56.32% compared with OS specimens, and the maximum permeability μm is increased to 1.908 k and the coercive force Hc is reduced to 91.32 A/m. The soft magnetic property damage caused by thermal stress is effectively improved after tempering at 315 ℃(WQ-TP). The maximum permeability μm of the WQ-TP specimens is further increased to 2.993 k and the coercivity Hc is reduced to 57.8 A/m, while maintaining excellent low expansion properties(α(20~100 ℃) = 0.54×10-6·K-1). Under the comprehensive consideration, the FeNi32Co5 alloy with excellent soft magnetic and low expansion properties can be obtained by water-cooled quenching and tempering after homogenized annealing.