Abstract On the basis of the order in which twinning occurs, twins are termed primary, secondary, and tertiary. In HCP materials, compression twins (CT) and extension twins (ET) are observed to form alternatively during sequential twinning. However, selections of twinning systems and variants are not yet fully understood. Both ET→CT→ET and CT→ET→CT sequences have been reported in literatures. Here we conduct a systematic and statistical study on the evolutions of twinning sequences and variants during cryogenic rolling of Ti. Both twinning sequences are observed in the same sample. Current statistical results indicate the selections of the twinning sequence and variants are governed by the following criteria: (1) the twinning sequence in an individual grain depends on its initial orientation; (2) the twin variant selection is mainly governed by the Schmid's law, although a few non-Schmid twins are observed along the short axis of the parent grains. These criteria are thought applicable to other HCP metallic materials.

中文翻译：

---

低温轧钛连续孪晶过程中孪晶系统和变体的演变

摘要 根据孪生发生的顺序，孪生被称为初级、次级和三级。在 HCP 材料中，观察到压缩孪晶 (CT) 和拉伸孪晶 (ET) 在顺序孪晶过程中交替形成。然而，尚未完全了解孪生系统和变体的选择。ET→CT→ET和CT→ET→CT序列均已在文献中报道。在这里，我们对 Ti 的低温轧制过程中孪晶序列和变体的演变进行了系统的统计研究。在同一样本中观察到两个孪生序列。目前的统计结果表明，孪生序列和变体的选择受以下标准控制：（1）单个晶粒中的孪生序列取决于其初始取向；(2) 孪生变体选择主要受施密德定律支配，尽管沿母粒短轴观察到少数非施密德孪生。这些标准被认为适用于其他 HCP 金属材料。