多晶纯钴退火组织中的孪晶转变规律研究

Twin Crystal Change Laws of Annealed Polycrystalline Pure Cobalt

主要是结合X射线衍射(XRD)技术以及电子背散射衍射(EBSD)技术,对不同退火温度下的多晶纯钴的退火组织的变化规律展开研究。结果表明:残留的多晶纯钴面心立方(fcc)结构的晶粒内部在退火过程中形成了∑3孪晶界,而且具有这种特征的晶粒数量随退火温度改变不大,基本趋于稳定;同时,具有密排六方(hcp)结构的晶粒内部在退火过程中形成大量的71.4°/<1120>特殊晶界。通过分析得知这种晶界形成的原因与fcc结构的晶粒中的∑3晶界的形成原因不同,是由fcc→hcp马氏体相变导致,即为相变孪晶。

The tissue variation of polycrystalline pure cobalt annealed at different temperatures was investigated by XRD and EBSD. The results show that Σ3 twin boundaries form in the residual fcc phase and the number of grains with such a characteristic almost does not change with annealing temperature. Meanwhile, 71.4°/1120 special boundaries appear in the grains with a hexagonal close-packed（hcp） structure during the annealing process. The formation reasons of the 71.4°/11 20 special boundaries are different from those of the Σ3 twin boundaries forming in the residual fcc phase; 71.4°/1120is formed as a result of phase transformation from fcc to hcp, following the Shoji-Nishiyama orientation relationship.