Abstract: Effect of annealing temperatures on the hardness and microstructure of high-purity scandium after forging was investigated by using microhardness measurement and optical microscope observation. The results show that the average grain size of the scandium metal generally shows an upward trend as increasing of the annealing temperature under the same annealing time, and the hardness first decreases and then tends to be stable. When the annealing temperature is lower than 725 ℃, the recovery and recrystallization process are relatively slow and the growth of average grain size is limited, while the microhardness continues to decrease with the increase of the annealing temperature, which reaches the lowest point at 725 ℃. While the annealing temperature is above 725 ℃, the higher the annealing temperature, the larger the average grain size, and the microhardness tends to be stable with the increase of annealing temperature. The optimum annealing process for the high purity scandium metal consists of heating at 725 ℃ for 30 min. After annealing at 725 ℃ for 30 min, the high purity scandium metal after forging is fully annealed, the grains is uniform with a grain size of 135 μm, and the hardness value decreases from 169.5 HV2 before annealing to 129.6 HV2 after annealing.

Key words: high purity scandium metal, annealing process, microstructure, hardness