材料辐照损伤中的点缺陷团簇与一维迁移现象

Clusters of point defects and one-dimensional motion of clusters during irradiation damage in materials

材料辐照损伤是核反应堆材料、尤其是核聚变堆材料所面临的重要问题.高能粒子(中子、离子、电子)辐照在材料中会产生大量的点缺陷,即自间隙原子和空位.这些点缺陷聚集在一起会形成自间隙原子团簇和空位团簇,从而对材料结构和性能的演化产生重要影响.空位团簇包括有空洞、层错四面体、空位型位错环,而自间隙原子团簇则只有自间隙型位错环.本文介绍了两种点缺陷团簇的性质、及其对于以材料辐照肿胀为主要内容的材料辐照损伤性能的影响.作为空位团簇,比较详细介绍了具有本课题组特色的空位型位错环的研究,同时分析了合金元素和氢同位素对空位型位错环的影响.在铁试样中形成的这种空位型位错环尺寸可达100 nm左右,该空位型位错环具有两种柏氏矢量,b=<100>和b=1/2<111>,前者的数密度比后者高一个数量级.对于自间隙原子团簇,则重点介绍了与其相关的一维迁移现象及其研究动态,该一维迁移性能有可能是影响高熵合金辐照性能的重要因素.

Irradiation damage in materials for nuclear reactors,particularly for fusion reactors,is a serious problem.For example,the pressure vessel in a fission power plant becomes brittle after exposure to neutron irradiation for many years.In the case of fusion reactors,in addition to the increase in ductile-to-brittle transition temperature,irradiation-induced swelling occurs in structural materials that need to tolerate high-dose irradiation of several hundreds of displacements per atom(dpa).The irradiation of particles(such as neutrons,ions,and electrons)with high energy introduces a large number of point defects,i.e.,self-interstitial atoms and vacancies,into materials.Such point defects aggregate together to form self-interstitial atom clusters as interstitial loop and vacancy clusters as void,stacking fault tetrahedra,or vacancy loop.Then,these clusters affect the microstructure and properties of materials.Moreover,these clusters play a more important role than individual point defects during the irradiation damage process.Even after research for decades,many questions about clusters remain unanswered partially because of the difficulties in irradiation test and cluster observation.This review paper explained the structures of clusters and the effect of clusters on irradiation damage in materials.As a unique research of this author’s group,the formation of vacancy-type dislocation loops with sizes of up to 100 nm in iron was introduced,including the effect of hydrogen and its isotope and the effect of alloy elements on the formation of vacancy-type dislocation loops.There are two different kinds of vacancy-type dislocation loops,i.e.,those having a Burgers vector of b=<100> and those having a Burgers vector of b=1/2<111>.The density of the first type is approximately one order of magnitude higher than that of the second type.The onedimensional motion of self-interstitial atom clusters and the research activities in this field were also discussed in detail,and the onedimensional motion would be a key factor effecting the irradiation damage of high entropy alloys.