This study investigates fatigue short crack growth in Zircaloy-4 alloy, revealing phenomena of twinning and detwinning of {$10\overline{1}2$$10\overline{1}2$}<$10\overline{1}1$$10\overline{1}1$> tensile type at the vicinity of the crack. Twinning primarily occurs at the crack tip, crack deflection sites, and adjacent heterogeneities such as grain boundaries and triple junctions. Both twinning and slip contribute simultaneously to crack tip plasticity. The occurrence of twinning significantly increases the average stress and stored energy density at the crack tip, thereby accelerating short crack propagation. Twinning forms earlier in Z-type samples (with the texture pole aligned with the Z-direction) compared to Y-type samples, resulting in an earlier and more pronounced increase in crack growth rate. Detwinning is observed exclusively in Z-type samples, induced by substantial changes in stress distribution at the crack tip, likely due to dislocation pile-up at the twin boundary during crack growth.

中文翻译：

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对锆合金疲劳短裂纹扩展过程中孪晶和解孪晶的机理见解


本研究研究了 Zircaloy-4 合金的疲劳短裂纹扩展，揭示了裂纹附近 { $10\overline{1}2$ }< $10\overline{1}1$ > 拉伸型的孪晶和脱孪晶现象。孪生主要发生在裂纹尖端、裂纹偏转位点和相邻的非均质性，例如晶界和三重结。孪晶和滑移同时影响裂纹尖端的塑性。孪晶的发生显著增加了裂纹尖端的平均应力和储能密度，从而加速了短裂纹扩展。与 Y 型样品相比，Z 型样品（织构极与 Z 方向对齐）更早形成孪晶，导致裂纹扩展速率更早且更明显地增加。仅在 Z 型样品中观察到双胞胎，这是由裂纹尖端应力分布的显着变化引起的，这可能是由于裂纹生长过程中孪晶界的位错堆积。