金属铍静态再结晶动力学研究

Static Recrystallization Kinetics of Metal Beryllium

摘要:

通过硬度法测量金属铍不同应变温度（250~450 ℃）、应变速率（10^–1~10^–4 s^–1）、真应变（0.16~0.92）压缩后再结晶分数，研究其在680~880 ℃退火静态再结晶组织演化及动力学。结果表明：降低应变温度和提高应变速率均可以促进铍再结晶进行；增加应变量，铍再结晶晶粒细化，再结晶速率也加快，但真应变大于0.60后，增加应变量对提高铍再结晶速率的影响变小；提高退火温度，铍再结晶速率明显加快，特别是退火温度从750 ℃提高到780 ℃时，铍再结晶速率急剧增加。880 ℃时，铍完成再结晶时间仅需约5 min。铍680~750 ℃的静态再结晶激活能为396.56 kJ·mol^–1，而780~880 ℃时激活能仅为72.93 kJ·mol^–1。建立具有修正Avrami指数n的铍静态再结晶动力学模型，模型计算值与实验值符合较好，能够较准确预测铍等温形变（250~450 ℃）后的静态再结晶分数，满足工程应用。

Abstract:

The microstructure evolution and the static recrystallization kinetics of metal beryllium during annealing at 680–880 ℃ were investigated. The isothermal compression test was conducted on an Instron 5582 testing machine and the recrystallized fraction of metal beryllium under varying strain temperatures (250–450 ℃), strain rates (10^–1–10^–4 s^–1), and true strains (0.16–0.92) was obtained. The results show that decreasing the strain temperature and increasing the strain rate can promote the progress of beryllium recrystallization. As the strain is increased, the beryllium recrystallized grains are refined, and the recrystallization rate is accelerated. However, the effect of increasing the strain on improving the recrystallization rate of beryllium is diminished when the true strain increases to more than 0.60. Increasing the annealing temperature, the recrystallization rate of beryllium is significantly accelerated. In particular, when the annealing temperature is elevated from 750 ℃ to 780 ℃, the recrystallization rate of beryllium enhances dramatically. At 880 ℃, the time for beryllium to complete recrystallization is reduced to approximately 5 min. The static recrystallization activation energy of beryllium is 396.56 kJ·mol^–1 at 680–750 ℃, while it is only 72.93 kJ·mol^–1 at 780–880 ℃. A static recrystallization kinetic model of beryllium with a modified Avrami component n is constructed. The calculated values of the model are in good agreement with the experimental values, which indicates that the model can accurately predict the static recrystallized fraction of beryllium deformed at 250–450 ℃, meeting the requirements of engineering applications.