Effects of Ion Irradiation on Laser Welded V-4Cr-4Ti Alloy

采用美国国家核聚变研究所研制的高纯V-4Cr-4Ti合金进行了实验研究。样品在1273K下退火2小时，并使用高纯度的Ar气体进行堆焊。在九州大学串列加速器上进行了2.4 MeV的铜离子辐照。从焊接材料中切下透射电子显微镜样品，在573K和873K下进行照射，最大剂量为12dpa。辐照前的显微组织表明，V-4Cr-4Ti合金中常见的较大的Ti(C，O，N)析出物消失在焊缝金属的中心。经873K离子辐照后，在0.75dpa剂量下观察到具有{100}习惯面的细小二氧化钛。在相同的辐照条件下，母材中的氧化物数密度较低。这意味着激光焊接过程中大量析出物中溶解的氧原子对V-4Cr-4Ti合金焊接组织的演变是至关重要的。

High purity V-4Cr-4Ti alloy, fabricated by National Institute for Fusion Science (NIFS), was used for this study. The samples were annealed at 1273K for 2 hours and bead-on-plate welds were performed using high purity argon gas. A 2.4MeV copper ion irradiation was carried out with the tandem accelerator at Kyushu University. The TEM samples were sliced from the welded materials and irradiated at 573K and 873K up to the dose of 12 dpa. The microstructure before irradiation showed that relatively large Ti(C, O, N) precipitates which were commonly observed in V-4Cr-4Ti alloy disappeared in the center of weld metal. After the ion irradiation at 873K, fine titanium oxides with {100} habit plane were detected at the dose of 0.75 dpa. Lower number density of the oxides was observed in the base metal after the same irradiation conditions. This means that the contribution of oxygen atoms, which dissolved from the large precipitates during the laser welding, is essential to the microstructural evolution of welded V-4Cr-4Ti alloys.