Delayed Hydride Cracking, DHC, is a mechanism that affects Zr and its alloys. Among other factors, thermal cycles may influence the occurrence of DHC process due to the difference between the hydrogen dissolution and precipitation solvus curves. In this work, DHC propagation rate (V_P) was measured in Zr-2.5Nb alloy, after different thermal cycles: 1) by cooling to the Test temperature (T_test); 2) by heating to T_test; 3) after cooling to different temperatures (T_cool) and subsequent heating to T_test = 253 °C and 154 °C. V_P measured after cooling followed Arrhenius behavior, and a change in the activation energy was detected around 170 °C. It was confirmed that, under the conditions tested in this report, DHC is not possible at temperatures higher than T_A = 210 °C when T_test is approached by heating. An undercooling of 25 °C was enough to avoid DHC at T_test = 253 °C. If T_test = 154 °C DHC could not be stopped by any undercooling. Experimental results of V_P and critical temperatures presented good agreement with values calculated with theoretical models reported in literature.

延迟氢化物开裂（DHC）是影响Zr及其合金的一种机制。除其他因素外，由于氢溶解和沉淀固溶曲线之间的差异，热循环可能会影响DHC过程的发生。在这项工作中，在不同的热循环后，测量Zr-2.5Nb合金中DHC的传播速率（V _P）：1）通过冷却至测试温度（T _test）；2）通过加热进行T_检验；3）冷却至不同温度（T _cool），然后加热至T _test后 = 253°C和154°C。V _P冷却后，按照Arrhenius行为进行测量，并在170°C附近检测到活化能的变化。可以肯定的是，在本报告中测试的条件下， 当通过加热接近T_测试时，在高于T _A = 210°C的温度下不可能进行DHC 。25°C的过冷度足以避免在T_测试 = 253°C时产生DHC 。如果T_测试 = 154°C，则任何过冷都无法使DHC停止。V _P和临界温度的实验结果与文献报道的理论模型计算得出的值具有很好的一致性。