材料期刊网

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。

Twin formation associated with grain boundary migration in recrystallized armcoiron has been studied by the method of vacuum etching.No noticable substructureswere observed after recrystallization at 750℃ for 5 hours.However,after reheatingfor a short time at 770℃,fine substructures appeared in most of the ferrite grains.During prolonged heating the substructure-free grains gradually grew at the expense ofthose possessing substructures.When the reheating temperature is raised close to theA_3 temperature,grain boundary migration is markedly accelerated.Two types of twins were observed during grain growth.One of them,probablyidentical in nature with ordinary annealing twins,has its non-coherent twin boundaryalways attached to the old grain boundary.Depending on the manner of migrationof the grain boundary and the non-coherent twin boundary,such type of twins maygrow,retreat,or even disappear.The other type of twins has a characteristic wedge-shaped twin boundary which is quite stable,and little change has been observed afterprolonged heating.