N. Igata

New dual-ion irradiation station at the University of Tokyo

Abstract The High-fluence Irradiation Test (HIT) facility of the University of Tokyo, under construction since 1983, was completed in the fall of 1985 with the assembly of the target station for dual-ion irradiation. The HIT facility was composed of two types of accelerators, viz., a Van de Graaff accelerator for light ions and a Tandem accelerator (Tandetron) for heavy ions. The target stations has some new and advantageous features for the measurement of irradiation parameters, e.g., ion-beam profile monitoring. The constitution of the dual-ion irradiation system of HIT is described together with a brief indication of the test results of a dual-ion experiment.

Internal friction peaks of cold worked and/or hydrogen charged 18-8 austenitic stainless steel

Abstract The cold work peak of the 18-8 stainless steel is different from the hydrogen peak. The cold work and hydrogen peak is considered to be the sum of the heights of the cold work peak and the hydrogen peak.

Effects of ε martensite and nitrogen on the damping property of high strength Fe–Cr–Mn alloys

Abstract The damping and strength property of Fe–12 mass% Cr–6 to 30 mass% Mn alloys has been investigated intending to develop a material which has high strength and high damping property. The effect of α′ (including α) and e martensite phase and γ matrix phase, which constitute the microstructure of cold rolled Fe–Cr–Mn alloys, on the damping property at room temperature has been investigated. A 50% cold worked Fe–12% Cr–22% Mn alloy indicated the largest volume fraction of e martensite phase and the highest damping property with high ultimate tensile strength of more than 1.2 GPa and 0.2% proof strength of about 0.9 GPa. Nitrogen effect on the damping property of the Fe–12% Cr–22% Mn alloys has been also investigated.

Internal friction of TiNi alloys produced by a lamination process

Abstract Recently, the demand for higher damping materials with higher strength has been requested from the precision machine industries. Of these materials, the TiNi alloy has excellent characteristics with high damping capacity and high strength. However, with respect to practical use, its cold rolling is difficult. In order to solve this problem, we examined the production of the TiNi alloy from the Ti–Ni laminated material by the solid-phase diffusion method. In this study, to investigate the best processing conditions to make a high damping TiNi alloy with high strength, the effects of the material composition, annealing time and cooling rate of the water quenching on the internal friction and tensile strength were examined. As a result, a material with an internal friction of δ=0.14 at 250 K and ultimate tensile strength about 800 MPa was obtained.

Development of SiC/Al composites as low activation materials

A SiC/Al composite using Continuous and multifilament-yarn SiC fibers (Nicalon) was investigated. The objectives of this investigation are to establish industrial basis for a SiC/Al perform wire, to evaluate neutron damage to the composite and to develop a SiC/Al composite for fusion reactor application. Mechanical properties were measured by tensile test, three point bending test and internal friction measurement. Microstructure were inspected by means of SEM, TEM and STEM-EDX. Under optimum conditions, we can obtain an average strength of 1.25 GPa for preform wires. Effects of neutron irradiation were studied using fission neutrons from JOYO and JMTR and with 14 MeV neutrons from RTNS-II. The SiC fibers showed excellent stability in dimensional changes by radiation damage. Increments of tensile strength and Youngs modulus was observed by irradiation in FBR (JOYO).

The effects of grain and specimen sizes on mechanical properties of type 316 austenitic stainless steel

Abstract The effects of grain size and specimen thickness on the mechanical properties (0.2% proof stress, ultimate strength, total elongation and work hardening exponent) of specimens of type 316 austenitic stainless steels have been investigated by tensile testing at room temperature. The 0.2% proof stress and the ultimate strength of thin specimens with small grain size (

Effects of nitrogen and carbon on void swelling in austenitic stainless steels

Abstract Void swelling of 316 austsnitic stainless steels and the effects of nitrogen and carbon were investigated by in-situ observation using a high voltage electron microscope. Specimens used were solution treated or 20% cold worked. Electron irradiation was performed at 600 C. Swelling increased linearly with dose after incubation period. In solution treated specimen, swelling decreased with nitrogen and carbon concentration, and this decrease was attributed to the decrease of the swelling rate rather than the incubation dose of swelling which was almost independent of nitrogen and carbon concentration. Void number density first decreased, and then increased with nitrogen and carbon concentration in solution treated specimen. Average void diameter exhibited reverse dependency, i.e. it first increased and then decreased. In cold worked specimen, the swelling rate was nearly the same as that of solution treated specimen in case of the same kind of steel, but the incubation dose became shorter than in solution treated specimen. Void number density increased and average void diameter decreased with nitrogen and carbon concentration in cold worked specimen. The differences between the contributions of nitrogen and carbon in solution treated specimens and those in cold worked specimens are discussed.

Electron beam welding of titanium and Ti-6AL-4V Thick plates

Abstract This paper reports work as thick weld process development for Ti and Ti alloys in fusion reactor applications. The materials used are pure Ti and Ti-6A1-4V with a maximum plate thickness of 56 mm I-butt welded by a 100KW electron beam welding facility at Osaka University. Optimum welding conditions produced sound welded I-butt joints without detectable defects by X-ray when evaluated with tensile test and micro-Vickers hardness test. The microstructures of the welded joints were investigated with TEM and SEM. These results showed that welded joints were quite sound and were possibly acceptable as structural components of fusion reactor even in as welded state.

Micro-computer system for quantitative image analysis of damage microstructure

Abstract Quantitative image analysis of radiation induced damage microstructure is very important in evaluating material behaviors in radiation environment. But, quite a few improvement have been seen in quantitative analysis of damage microstructure in these decades. The objective of this work is to develop new system for quantitative image analysis of damage microstucrure which could improve accuracy and efficiency of data sampling and processing and could enable to get new information about mutual relations among dislocations, precipitates, cavities, grain boundaries, etc., In this system, data sampling is done with X-Y digitizer. The cavity microstructure in dual-ion irradiated 316 SS is analyzed and the effectiveness of this system is discussed.

The effect of rhenium on some properties of molybdenum alloys as fusion reactor material

Abstract In this study, the effect of Re on the mechanical behavior of the base metal and welds at 25°C and 500°C and the effects under electron irradiation in a high voltage electron microscope were investigated. The merits of Re addition were: Strengthening by solution hardening and increase of ductility of both base metal and welds. Under irradiation, the rate of increase of dislocation density was reduced and swelling was suppressed. These effects were well understood from microstructural standpoints. Rhenium is considered to be an effective alloying element in improving Mo for fusion reactor use.