Effects of microstructural anisotropy and helium implantation on tensile properties of powder-metallurgy processed tungsten plates
Effects of microstructural anisotropy and helium implantation on tensile properties of powder-metallurgy processed tungsten plates
复制标题
微观结构各向异性和氦注入对粉末冶金加工钨板拉伸性能的影响
DOI：
10.1016/j.nme.2022.101122
复制
发表时间：
2022
影响因子：
2.6
通讯作者：
Hasegawa Akira
中科院分区：
文献类型：
--
作者：
Miyazawa Takeshi;Matsui Kento;Hasegawa Akira
粉末冶金（PM）处理的钨（W）材料进行轧制正在开发的整体偏滤器的聚变反应堆。PM-W表现出高位错密度、细晶粒和层状晶粒结构，这是由轧制工艺引入的。利用PM-W在低温下的脆性，可望改善其组织控制。然而，众所周知，在轧制金属中，晶粒结构取决于轧制比、方向和温度。这可能导致机械性能的各向异性。本研究的目的是阐明组织各向异性和氦（He）注入对PM-W板拉伸性能的影响。对轧制和消除应力后的PM-W板进行了检测。沿以下三个方向沿着制备微型拉伸试样：拉伸方向平行于轧制方向（L.D.），垂直于轧制方向（T.D.），并且平行于厚度方向（S.D.）。He离子注入实验是利用回旋加速器的50 MeV He ~（2+）离子束进行的。注入的He浓度约为20 appm。在100-1100 °C下进行拉伸试验，并通过扫描电子显微镜观察破裂表面。根据接收状态的结果，在低于500 °C的温度下的总延伸率的情况下观察到微观结构各向异性。在沿着S.D.的量规截面边缘处观察到由于晶间断裂而形成的裂纹，在拉伸断裂行为中观察到各向异性。假设裂纹倾向于沿着晶界层传播。虽然延展性沿T. D.沿着方向几乎保持不变。He注入后，沿着S.D.观察到延展性降低和脆性断裂。因此，He对裂纹扩展的影响沿S.D.沿着是显著的。
Powder metallurgy (PM)-processed tungsten (W) materials subjected to rolling are being developed for the monoblock divertors of fusion reactors. PM-W exhibits high dislocation density, fine grains, and a layered grain structure, which is introduced by the rolling process. It is expected that its microstructure control will be improved by the brittleness of PM-W at low temperatures. However, it is well known that, in rolled metals, the grain structure depends on the rolling ratio, direction, and temperature. This can cause anisotropy in the mechanical properties. The purpose of this study was to elucidate the effects of microstructural anisotropy and helium (He) implantation on the tensile properties of PM-W plates. The PM-W plates subjected to rolling and stress relief were examined. Miniature tensile specimens were prepared along the following three directions: the tensile directions were parallel to the rolling direction (L.D.), perpendicular to the rolling direction (T.D.), and parallel to the thickness direction (S.D.). The He implantation experiments were performed using a 50 MeV He2+ion beam of a cyclotron accelerator. The implanted He concentration was approximately 20 appm. Tensile tests were conducted at 100–1100 °C and the ruptured surfaces were observed by scanning electron microscopy. From the results of the as-received condition, microstructural anisotropy was observed in the case of total elongation at temperatures lower than 500 °C. Cracks formed owing to intergranular fracture were observed at the edges of the gauge section along S.D., and anisotropy was observed in the tensile fracture behavior. It is assumed that the cracks tend to propagate along the layers of the grain boundaries. Although the ductility remained almost unchanged along the T.D. after He implantation, a decrease in ductility and brittle fracture were observed along the S.D.. Thus, the effect of He on crack propagation was significant along the S.D..