钽板退火过程中的储存能演变与再结晶行为

The Stored Energy Evolution and Recrystallization Behavior of Tantalum Plate During Annealing

对高纯钽板分别进行单向轧制和周向轧制,得到了87%变形量的样品。将单向轧制和周向轧制样品各分为两组。其中,一组样品随炉升温至800℃进行预回复处理,然后在1 300℃保温30 min进行再结晶退火处理;另一组则直接进行再结晶退火处理。应用X射线峰形分析(XLPA)定量计算两种轧制方式下钽板的宏观储存能,结合电子背散射衍射(EBSD)和透射电子显微镜(TEM)技术表征其预回复及再结晶微观组织,同时半定量地评估不同取向晶粒预回复后的微观储存能。结果表明:87%周向轧制钽板经过800℃预回复处理后,{111}([111]//ND,ND为板法向)与{100}([100]//ND)取向晶粒内部的储存能差别明显减小,后续再结晶晶粒更为均匀细小且基本呈等轴状。这主要是由于低温预回复处理使得亚晶形核机制成为钽再结晶形核的主导机制,同时基体内储存能的释放极大降低了后续再结晶驱动力及晶粒长大速率。

High purity tantalum plates were deformed to 87% reduction in thickness by unidirectional rolling and clock rolling,respectively.The resultant specimens were divided into two groups.One was pre-recovered at 800 ℃ in a furnace,and then was annealed at 1 300 ℃ for 30min to generate completely recrystallized microstructure,while the other group was annealed and recrystallized without any treatment.X-ray line profile analysis (XLPA) was adopted to quantify the bulk stored energy of tantalum plates under the above-mentioned two different rolling methods.Aided by the electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM),the microstructures of pre-recovered and recrystallized tantalum plates were characterized,and the local-region stored energies of differently oriented grains in the pre-recovered samples were evaluated.The results showed that the stored energy gap of {111}([111]//ND,ND is normal direction) and {100}([100]//ND) orientation grain decreased obviously when 87% clock-rolled tantalum plates experienced 800 ℃ pre-recovery treatment.Meanwhile,the subsequent recrystallization grains were more homogeneous and equiaxial.This can be attributed to the subgrain-nucleation-dominated recrystallization mechanism induced by the introduction of low-temperature pre-recovery treatment,and moreover,the considerable decline of recrystallization driving force resulted from the release of stored energy in the matrix.