中间热处理对Zr-1Nb-0.2Y合金在420℃空气中氧化性能的影响

EFFECT OF THE INTERMEDIATE HEAT TREATMENT PROCESSES ON THE OXIDATION CHARACTERISTICS OF Zr-1Nb-0.2Y ALLOY IN 420 ℃ AIR

研究了中间热处理工艺对Zr-1Nb-0.2Y(质量数,%)合金在420℃空气中氧化性能的影响.结果表明,通过变形及适当的多道次退火,可以有效控制合金化元素的析出,最终获得合理组织与最佳性能.随轧制及热处理道次加深,合金的抗氧化性能逐渐提高,由中间退火工艺为640℃,3 h+570℃,3 h得到的最终样品具有最优的抗氧化性能.合金的位错密度对氧化性能的影响并不显著.TEM形貌观察以及沉淀相EDS分析表明,中间热处理工艺通过影响沉淀相的体积分数、平均尺寸、合金化元素Nb+Y含量(平均含量与总含量)等因素来影响Zr-1Nb-0.2Y合金的氧化性能.沉淀相的体积分数、尺寸和合金元素含量等因素通过协同作用共同影响Zr-1Nb-0.2Y合金的氧化性能.

Zr- based alloys have been used as cladding tubes in nuclear reactors for several decades due to their superior mechanical properties, good corrosion resistance and low neutron absorption cross-section. Zr alloys consist of hcp-structured a-Zr matrix and dispersed precipitate particles. These precipitate particles play a key role in improving the service performance of the alloy. In general, the manufacturing of Zr-based alloy tubes or sheets involves a series of deformation and annealing processes, which lead to a modification of the precipitate particles in size and distribution and an improvement of comprehensive properties of the alloys. In this work, the effect of intermediate heat treatment processes on precipitate particles and air oxidation characteristics of Zr-1Nb-0.2Y（mass fraction, %） alloy was studied. With increase of rolling and annealing times, the oxidation resistance of Zr- 1Nb-0.2Y alloy was improved. The final product from manufacturing route II with intermediate annealing process of640 ℃, 3 h＋570 ℃, 3 h was proved to be most resistant to oxidation in 420 ℃ air. TEM images and EDS results showed that relevant parameters such as precipitate particle volume fraction, precipitate particle mean diameter,Nb＋Y content（including mean content and total content） in precipitate particles were modified by intermediate annealing processes, which essentially influenced the oxidation characteristics of Zr-1Nb-0.2Y alloy. The smaller the mean size of precipitate particle and the higher the Nb＋Y content in the precipitate particle are, the better the resistance to air oxidation of Zr-1Nb-0.2Y alloy.