Nuclear Science User Facilities 62 Task 2. Microstructural characterization of the prepared specimens.TEM studies were carried out on the preparedTEM specimens using theTecnaiTF30-FEG S-Twin STEM to study the ion irradi- ated microstructure with particular attention to both the irradiation induced damage formation and the morphology and chemical analysis of the nanometric particles.The APT studies, conducted using the Cameca LEAP 4000X HR, provided information on any change in their size, number density, and composition as a function of dpa and irradiation temperature. Task 3. Nano-indentation testing. Heavy ion irradiation led to only about a micron thick surface damage layer. Hence, the nano-indentation tech- nique served as an effective method to characterize mechanical property, such as elastic modulus and hardness of the ion irradiated damage layer.A Hysitron TI-950Tribo-indenter available in MaCS was used for these experiments. Accomplishments The goal of the project was to examine the microstructure and mechanical properties of the 14LMT alloy irradiated with different radiation damage doses (100–400 dpa). Ion irradiation experiments on the 14LMT specimens were carried out by Dr. Lin Shao and his graduate student, Lloyd M. Price, at theTexas A&M University. Jatuporn Burns helped with the preparation ofTEM and APT specimens using the FIB available at CAES-MaCS. Dr.Yaqiao Wu helped the graduate students (Somayeh Pasebani and Ankan Guria) perform theTEM experiments and APT analyses of the irradiated specimens of 14MLT.This research was primarily conducted by graduate students Somayeh Pasebani and Ankan Guria. JoannaTaylor was instrumental in facilitating our access to MaCS. Figure 2. Three-dimensional reconstructed atom probe tomography maps of 14LMT alloy specimen irradiated by ferrous ions to 300 dpa at 748 K.