1J79 alloy belongs to Permalloy, which is one of the iron-nickel soft magnetic alloy series. It has the characteristics of high magnetic permeability and low coercivity, and is widely used in the production of electronic components with high sensitivity, precise size, small size, low high-frequency loss and good time and temperature stability. Since the alloy is very sensitive to stress, in order to give full play to its magnetic properties, it must be annealed before use. In addition to chemical composition and smelting process, factors such as temperature, holding time, annealing mode and cooling method during heat treatment also have a great influence on magnetic properties. Therefore, it is very necessary to conduct in-depth research on the two-stage continuous annealing process to improve its magnetic properties and obtain higher saturation magnetization and low coercivity for the heat treatment process of 1J79 alloy.
The 1J79 alloy samples were melted in a vacuum induction furnace and a vacuum non-consumable arc furnace to ensure the uniformity of the alloy composition and structure. After loading, the vacuum was evacuated to 10^−2 Pa, and then argon was filled for protection. The reaction heating temperature was adjusted by controlling the size of the current. After the melting was completed, the alloy was cooled into an ingot with the furnace. Subsequently, it was forged into a 2mm thick block in the temperature range of 900∼1100 °C. Then, different annealing processes were carried out in a tubular hydrogen annealing furnace (such as 1100 °C×xh furnace cooling; 950 °C×3h+1100 °C×3h furnace cooling). During annealing, the sample was placed in a quartz tube, hydrogen was passed through for about 20 minutes, and the power supply was turned on for heating after the air in the tube was washed. When the furnace temperature rose to the set temperature, the current was adjusted to make the sample enter the best insulation state. After the insulation was completed, the heating power was disconnected, and the sample was cooled to room temperature with the furnace in a hydrogen atmosphere.
After the sample is annealed, it is polished. The impurity content is observed by electron probe (EPMA-1600), the grain growth is observed by optical microscope, and the hysteresis loop of the sample is measured by vibrating sample magnetometer (VSM). Then the magnetic properties are compared and the annealing process with the best magnetic properties is selected.