Abstract

X-ray diffraction studies were conducted to examine changes in the structural-phase state and dislocation density of Ti_49.8Ni_50.2 alloy depending on the isochronal annealing temperature after severe plastic deformation by abc pressing at 573 K. The total true strain achieved in the alloy specimens during abc pressing was e = 9.55. Isochronal annealing was carried out for 1 h at 573, 673, 773, 873 and 973 K. Analysis of all studied specimens at room temperature revealed the coexistence of R and B19′ phases, whose relative fractions varied with annealing temperature. The high-temperature B2 phase was not detected. It was found that the most rapid decrease in the dislocation density, which was measured at 393 K (in the B2 state), occurred after annealing at 673 and 773 K. Specimens annealed at 773 K had the minimum dislocation density, which is more than an order of magnitude lower than the dislocation density immediately after abc pressing. In the same temperature range, there is a significant decrease in the root-mean-square B2 lattice microdistortions <ε²>^1/2 and a slight increase in the average size of coherently diffracting domains (crystallities). After abc pressing and isochronal annealing, the main contribution to the intrinsic X-ray line broadening is made by B2 lattice microdistortions, while the contribution from crystallite size is insignificant. The obtained results show that intense recrystallization in Ti_49.8Ni_50.2 alloy after abc pressing at 573 K begins at T ≥ 773 K.

中文翻译：

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Ti49.8Ni50.2合金在573 K下进行剧烈塑性变形后随等时退火温度变化的结构相状态和位错密度

摘要

_{进行 X 射线衍射研究，以检查 Ti 49.8} Ni _50.2合金在 573 K 下进行 abc 压制发生严重塑性变形后，结构相状态和位错密度随等时退火温度的变化。合金中实现的总真实应变abc 压制过程中的样本e = 9.55。在 573、673、773、873 和 973 K 下进行等时退火 1 小时。对所有研究样品在室温下的分析表明 R 相和 B19' 相共存，其相对分数随退火温度的变化而变化。未检测到高温B2相。结果发现，在 673 K 和 773 K 退火后，在 393 K（B2 状态）下测得的位错密度下降最快。在 773 K 退火的样品具有最小位错密度，超过比 abc 压制后的位错密度低一个数量级。在相同温度范围内，均方根B2晶格微畸变<ε ² > ^1/2显着降低，相干衍射域（晶体）的平均尺寸略有增加。经过abc压制和等时退火后，B2晶格微畸变对本征X射线线展宽的主要贡献，而微晶尺寸的贡献微不足道。结果表明，Ti _49.8 Ni _50.2合金在 573 K 下进行 abc 压制后，在T ≥ 773 K时开始剧烈再结晶。