Abstract Intercritical tempering at 680 °C for different times was carried out in a low carbon copper-bearing steel to study the evolution of the crystal structure of Cu precipitates by high resolution transmission electron microscopy. With increased tempering time, four different types of crystal structure of copper precipitates with different sizes were observed, namely, (a) nano-ordered clusters comprised of B2 FeCu nano-ordered clusters (2–3 nm) and weak ordered BCC Cu nanoclusters (2–3 nm), (b) 9R Cu (5–12 nm) - multiple twinned structure consisted of two, six or seven 9R twins with an orientation relationship of (1 1–4) 9R ∥(0 1 1) α , [− 1 1 0] 9R ∥[1 − 1 1] α , (c) detwinned 9R Cu (24–26 nm) consisted of two 9R parts and a removable interface (1 1–4) 9R , and (d) FCC Cu (~ 37 nm) precipitates consisted of two parts of FCC Cu and a micro-twinned region. The evolution sequence of crystal structure of Cu precipitates was: nano-ordered clusters → 9R Cu → detwinned 9R Cu → FCC Cu. The maximum contribution to precipitation hardening is attributed to nano-ordered clusters.

中文翻译：

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低碳钢中Cu析出物晶体结构的演变

摘要 对低碳含铜钢进行680 °C不同时间的临界间回火，通过高分辨透射电子显微镜研究Cu析出物晶体结构的演变。随着回火时间的增加，观察到四种不同类型的不同尺寸的铜沉淀物的晶体结构，即（a）由 B2 FeCu 纳米有序簇（2-3 nm）和弱有序 BCC Cu 纳米簇组成的纳米有序簇（ 2–3 nm), (b) 9R Cu (5–12 nm) - 由两个、六个或七个 9R 孪晶组成的多重孪晶结构，取向关系为 (1 1–4) 9R ∥(0 1 1) α ， [− 1 1 0] 9R ∥[1 − 1 1] α , (c) 分离的 9R Cu (24–26 nm) 由两个 9R 部分和一个可移除的界面 (1 1–4) 9R 组成，(d) FCC Cu (~ 37 nm) 沉淀物由两部分 FCC Cu 和一个微孪晶区域组成。Cu析出物晶体结构演化顺序为：纳米有序簇→9R Cu→解孪9R Cu→FCC Cu。对沉淀硬化的最大贡献归因于纳米有序簇。