The effect of cold work on the transformation kinetics and texture of a zirconium alloy during fast thermal cycling
The effect of cold work on the transformation kinetics and texture of a zirconium alloy during fast thermal cycling
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DOI：
10.1016/j.msea.2019.01.047
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发表时间：
2019-02-11
期刊：
影响因子：
6.4
通讯作者：
da Fonseca, Joao Quinta
中科院分区：
文献类型：
--
作者：
Chi-Toan Nguyen;Romero, Javier;da Fonseca, Joao Quinta
研究了冷加工对稀锆合金快速循环后相变动力学和织构演变的影响。研究发现，冷加工延迟了相变的开始，并有助于相变后织构的随机化。在两种条件下，将冷轧至70%的变形量并完全再结晶的锆合金样品以100摄氏度的快速度加热到S(-1)的贝塔上方，使用阻性加热，没有约束。用电阻率法测量了加热过程中的相组成，用电子背散射衍射法测量了热循环前后的织构。以前对钛的研究表明，冷加工会导致相变后织构的加强，而这些新的实验表明，当加热速度足够快时，再结晶在加热时不完全，这减缓了相变的开始，导致冷却后随机的阿尔法织构。再结晶材料在贝塔热处理后的织构是非随机的，但与开始时不同，这既是由于晶粒长大后更强的贝塔织构，也是冷却时更强的变种选择的结果。这种变体的选择主要可以用特殊的贝塔晶界的α形核来解释。这些结果表明，在加热速度较快的情况下，预先变形对贝塔热处理后产生的织构有很大的影响。这意味着核包层组件在失去冷却剂(LOCA)和反应性引发事故(RIA)后的各向异性，但也更广泛地适用于使用焊接或加热率较高的附加层制造的锆和钛的制造。
The effect of cold-work on the transformation kinetics and texture evolution after fast temperature cycling were studied in a dilute zirconium alloy. It was found that cold-work delays the onset of phase transformation and helps randomise the texture after the transformation. Samples of Zircaloy-4 in two conditions, cold-rolled to 70% reduction and fully recrystallised, were heated above the beta-transus at a fast rate of 100 degrees C s(-1) using resistive heating and without constraint. Electrical resistivity was used to measure the phase fraction during heating and electron back-scatter diffraction was used to measure the texture before and after the thermal cycle. Whereas previous work on titanium suggested that cold-work leads to texture strengthening after transformation, these new experiments show that, when the heating rate is fast enough, recrystallisation is incomplete on heating, which slows down the start of transformation, leading to a random alpha-texture after cooling. The texture in the recrystallised material after beta heat-treatment is non-random but different from the start, a consequence of both a stronger beta-texture after grain growth and stronger variant selection on cooling. This variant selection can be mostly explained by alpha-nucleation at special beta-grain boundaries. These results demonstrate that prior deformation has a strong effect on the textures produced after beta-heat treatment when heating rates are fast. This has implications for the anisotropy of nuclear cladding components after loss-of-coolant (LOCA) and reactivity initiated accidents (RIA) but also more widely for the manufacturing of zirconium and titanium using welding or additive layer manufacturing where the heating rates are high.