冷却方式对超因瓦合金热膨胀与软磁性能的影响研究

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 °C 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 °C) of the WQ specimens is 0.38×10^-6·K^-1 at 20∼100 °C, 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 H_c is reduced to 91.32 A/m. The soft magnetic property damage caused by thermal stress is effectively improved after tempering at 315 °C(WQ-TP). The maximum permeability μ_m of the WQ-TP specimens is further increased to 2.993 k and the coercivity H_c is reduced to 57.8 A/m, while maintaining excellent low expansion properties(α_{(20∼100 °C)} = 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.