锆合金因综合性能优异而被广泛用作轻水堆的燃料包壳材料。 核反应堆运行期间，包壳不可避免地从高温冷却剂中吸氢。 传统认知认为，在无外部载荷作用下，氢化物倾向于沿管材周向析出；仅当施加外部拉应力时才会发生再取向形成径向氢化物。 然而，本研究表明，在无外部机械载荷条件下，过高的升温速率亦可诱发显著的氢化物再取向行为。 实验结果显示，当升温速率提升至 20 ℃/min 时，管材外壁形成宏观可见的径向氢化物聚集区，呈现特征性的“太阳斑”状形貌。 分析表明，快速升温在管壁厚度方向上建立了陡峭的温度梯度，致使外壁因受内壁约束而产生动态环向拉应力；该应力场不仅驱动固溶氢向高拉应力区发生“上坡扩散”，更诱导氢化物在过饱和状态下垂直于拉应力方向择优析出。

Zirconium alloys are widely used as fuel cladding in light water reactors because of their optimal combination ofmechanical strength, corrosion resistance, and low neutron absorption cross-section. During operation, cladding inevitablyabsorbs hydrogen from the high-temperature coolant. Conventionally, hydride precipitates exhibit a circumferentialorientation under stress-free conditions, and reorientation into a radial morphology is traditionally attributed to sustainedtensile hoop stress. Here, it is demonstrated that pronounced hydride reorientation can occur under stress-free conditions,triggered solely by rapid thermal transients. The experimental results reveal that at a heating rate of 20 ℃/min, a localized,radially oriented hydride aggregation zone—resembling a “sunspot”—emerges on the outer cladding surface. Mechanisticanalysis indicates that rapid heating establishes a steep through-thickness temperature gradient, which, under deformationcompatibility, forces the expanding outer wall to be constrained by the inner wall and consequently drives a dynamiccircumferential tensile stress gradient. This transient gradient drives solute hydrogen toward regions of higher tensile stressvia uphill diffusion and triggers rapid precipitation in the supersaturated matrix, preferentially aligning hydridesperpendicular to the principal tensile axis.