铌对氢化锆裂纹行为和氢含量的影响

Effect of Nb on Cracking and Hydrogen Content of Zirconium Hydride

氢化锆是一种理想的固体中子慢化材料,尤其适用于空间核电源的反应堆,但是高氢含量的氢化锆在制备过程中很容易形成裂纹。Nb是氢化锆中的主要添加元素,对氢化锆的裂纹形成和氢含量有一定影响,这是由Nb在氢化锆中的存在形式决定的,对此进行了研究。结果表明,在吸氢充分的情况下,不同Nb含量的Zr-Nb合金氢化后产物的主要组成都是ZrH2,ZrH1.950和ZrH1.801的ε相氢化锆混合物,Nb的添加对氢化锆的晶格常数和晶胞大小影响不大。Nb改善了氢化锆的多缺陷状态,减少了氢富集的位置,从而起到抑制裂纹产生的作用。常压下,Nb的添加会影响合金的最大吸氢量,尤其当Nb含量在10%以上时,会生成低氢含量的NbHx固溶体,影响锆合金的整体吸氢量。Nb在氢化锆中的固溶度较小,Nb含量较低时,大部分Nb以白色含H锆铌固溶体小颗粒的形式弥散分布在氢化锆表面。

Zirconium hydride was one of the most ideal moderators,especially for the space nuclear power system.But the high hydrogen level zirconium hydride was easy to crack during its preparation.Nb was the main adding element in the zirconium hydride moderator and affected the cracking behaviors and hydrogen content of the zirconium hydride,which was determined by the existing status of Nb in the zirconium hydride.The issues mentioned were investigated at present.It indicated that the hydriding products of Zr-Nb alloys with different Nb content were all composed of mixed ε phase zirconium hydrides of ZrH2,ZrH1.950 and ZrH1.801.Nb improved the structure and morphology of the zirconium hydride,decreased the defects and inhibited the cracking.In the case of high Nb level,the generated NbHx solid solution with low hydrogen content downgraded the whole hydrogen content of the alloy.The solubility of Nb in the zirconium hydride was low.For the zirconium hydride with low Nb content,majority of Nb was scattered on the surface of the zirconium hydride as small white grains of H-containing Zr-Nb solid solution.