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应用真空热侵蚀方法,研究Armco铁晶粒长大晶界迁移过程中,退火孪晶形成的过程。观察到在低于A_3点退火后,在了770℃短时间保温,多数α-铁素体晶粒内出现细小亚结构。随着加热时间的延长,具有细小亚结构的晶粒逐渐消失,原先不含亚结构的晶粒,则逐渐长大。将加热温度提高至A_3点附近,显著加速晶界迁移的过程。在长大的晶粒中,出现两类退火孪晶。一类的性质与一般退火孪晶相似,似其非共格孪晶界经常出现于旧晶界附近。视晶粒间界与非共格孪晶界迁移的情况,这类退火孪晶在保温过程中,可能随晶界迁移而伸长,亦可能随非共格孪晶界迁移而变细或消失。另一类孪晶的特点是一端在晶粒间界上,另一端呈楔状。楔状孪晶界很稳定,在保温过程中,未发现任何变化,在晶粒间界上的一端,则与晶粒间界一起,发生迁移。根据观察结果,认为α-铁中退火孪晶形成的机构与Burke及Furnbull所提出的面心立方金属中退火孪晶形成的机构相似,退火孪晶的形成与晶粒间界迁移有密切关系。
The vacuum thermal erosive method was used to study the formation of annealing twins during the grain boundary growth of Armco iron grains. It was observed that after annealing at a temperature below A 3 for a short time at 770 ℃, most of the α-ferrite grains showed fine sub-structure. With the extension of heating time, the grains with fine sub-structure gradually disappear, the original without sub-structure grains, then gradually grow. The heating temperature increased to near A_3, significantly accelerate the process of grain boundary migration. In the grown grains, two types of annealed twins appear. A class of properties similar to the general annealing twins, like the non-coherent twin boundaries often appear in the vicinity of the old grain boundaries. Depending on the migration of grain boundaries and non-coherent twin boundaries, such annealing twin may elongate with the grain boundary during the heat preservation process, and may also become thinner or disappear with the non-coherent twin boundary migration . Another type of twin is characterized by one end on the grain boundaries and the other end wedge-shaped. The wedge-shaped twin boundaries are very stable. During the heat preservation process, no changes were found. At one end of the grain boundaries, the wedge twin boundaries migrated along with the grain boundaries. According to the observation, it is considered that the formation mechanism of annealing twins in α-iron is similar to the mechanism of annealing twins formed by Burke and Furnbull in the face-centered cubic metal. The formation of annealing twins is closely related to the grain boundary migration.