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Thermal aging experiment is an effective method to evaluate the thermostability of structure materials which serve in high temperatures. But it difficult to acquire the aging data throughout service term, because it would take a long time. Hence, an accelerating thermal aging model of China low activation martensitic (CLAM) steel was built in this paper to shorten the time of the thermal aging experiment. The microstructure analysis and Charpy impact tests were conducted on CLAM steel after thermal aging with different temperatures. The results showed that raising temperature could accelerate the grain coarsening process and the main factor of ductile-to-brittle transition temperature (DBTT) increasing was grain coarsening after aging for less than 8000 h which were analyzed by fracture model. Hence, the activation energy of grain coarsening with a value of 47.4 kJ/mol could be regarded as the activation energy of thermal aging. Then a model of accelerating thermal aging was built by using Arrhenius formula to evaluate the properties degradation during thermal aging. This strategy could be used to accelerate thermal aging process of CLAM steel through raising aging temperature and it could save time and cost for aging experiment. [ABSTRACT FROM AUTHOR]

Abstract: The first wall (FW) of China dual functional lithium lead-test blanket module (DFLL-TBM) for International Thermonuclear Experimental Reactor (ITER) contains rectangular helium flow channels, which will be fabricated by hot isostatic pressing (HIP)-diffusion welding with China low activation martensitic (CLAM) steel plates and rectangular tubes. Study on the rectangular tube fabrication process are being conducted. Rectangular tubes of 15mm×20 (inter dimensions of cross section)mm×2.2 (wall thickness)mm×1500 (length)mm were produced by hot piercing and cold rolling, and its dimensional deviation met the requirement of TBM assembly. The effects of tube rolling and heat treatment on microstructure and mechanical properties of CLAM rectangular tube were analyzed. It is found that soft annealing heat treatment after tube piercing was a suitable way to improve the ductility of the CLAM steel. The elongation should be less than 15% at every tube rolling step, and the favorable tempering temperature to release the stress caused by tube rolling was 800°C. [Copyright &y& Elsevier]

Abstract: The effect of the size and distribution of non-metal inclusions on mechanical properties of the China low activation martensitic steel (CLAM) was investigated. The tensile and Charpy V-notch impact tests showed that electroslag remelting improved the tensile properties and reduced the ductile brittle transition temperature (DBTT). Inclusion detection of CLAM by optical microscopy and scanning electron microscope showed that both the dimensions and quantities of the alumina inclusions decreased and their distributions became more uniform after remelting. The better refinement and distribution uniformity of alumina inclusions were considered as the main possible reasons for the improvement of the mechanical properties of CLAM steel after remelting. [Copyright &y& Elsevier]

This paper highlights the results of a study on the high cycle fatigue strength and fracture mechanism of China Low Activation Martensitic (CLAM) steel. The high cycle fatigue test results showed that the fatigue strength of CLAM steel decreased with the temperature, and the condition fatigue strengths ( N = 10 7 ) were 275 MPa and 235 MPa at 723 K and 823 K, respectively. The fractograph results indicated that the fractures were mainly initiated from the surface of the specimen. [ABSTRACT FROM AUTHOR]

Dissimilar welding between China low activation martensitic (CLAM) steel and 316L austenitic stainless steel was investigated to achieve the reliable connection between test blanket modules (TBMs) and piping system in the international thermonuclear experimental reactor (ITER). The dissimilar joints were welded by tungsten inert gas (TIG) welding process with a filler material type-309. In order to stabilize the microstructure and improve the strength and toughness, post-weld heat treatments (PWHTs) of tempering at 740 °C, 780 °C and 820 °C, respectively, for 2 h were performed. The microstructure observation showed that tempering at 740 °C for 2 h was the preferable PWHT rule in this work. After the treatment, the hardening in heat affected zone (HAZ) on the CLAM steel side decreased remarkably. The tensile strength of the joint was roughly the same as that of the base metal. The impact toughness of HAZ on the CLAM steel side was 77% of that of the base metal. The absorbed energy of HAZ of 316L steel decreased by 93 J, and that of weld metal (WM) was 110 J after the treatment. [ABSTRACT FROM AUTHOR]

Abstract: The microstructure of China Low Activation Martensitic steel (CLAM) and its influence on mechanical properties were investigated. The tensile test showed that the strength of CLAM (HEAT 0603A) was higher than that of HEAT 0408B at room temperature, and the reverse results were obtained at elevated temperatures. The results indicated that the microstructure was composed of dispersived carbide particles and lath martensite with high dislocation density. The main precipitation phases were Cr-rich M23C6 carbides precipitated mainly along the lath boundaries and prior-austenite grain boundaries and Ta-rich MX particles precipitated mainly in the laths and lath boundaries. The finer lath was the main reason for the higher strength of HEAT 0603A compared with HEAT 0408B at room temperature; contrasted with the lower strength at high temperature. Heavier hot forging deformation degree was considered as the main possible reason for the decrease of martensite lath width in HEAT 0603A. [Copyright &y& Elsevier]

Abstract: The China Low Activation Martensitic (CLAM) steel is being developed in ASIPP (Institute of Plasma Physics, Chinese Academy of Sciences) under wide collaboration with many institutes and universities. A heat of 1.2 tons was fabricated and tested. The tested main compositions are eligible and without segregation. The tensile, Charpy impact and fracture toughness tests showed that its mechanical properties were similar to those of small ingots of CLAM steel. Also, joining techniques such as Electron Beam Welding (EBW), Hot Isostatic Pressing–Diffusion Welding (HIP–DW) and fabrication techniques of rectangular tube with CLAM steel were studied in details. And a 1/3 scaled mockup of Test Blanket Module (TBM) by P91 are being fabricated to explore TBM fabrication technology. [Copyright &y& Elsevier]

Abstract: Liquid LiPb eutectic is one of the promising candidate tritium breeder materials for fusion reactors. This paper presents the progress in compatibility experiments with liquid LiPb achieved up to now in China for some candidate structural materials. The results showed that CLAM steel had good compatibility with flowing LiPb at 480°C with the velocity of 0.08m/s after 5000h in DRAGON-I loop. On the other hand, after exposed in static LiPb at 700°C for 500h in a SiC crucible, the W and Mo specimens suffered much more weight loss compared with Nb specimen, and a thin reaction product layer was visible on the surface of all the three refractory metals. Preliminary analysis on SiCf/SiC composite specimens indicated that there was no penetration of LiPb and no reaction products on the surface with CVD SiC coating, which showed SiCf/SiC composite were stable and compatible with static LiPb under 700°C after 500h exposure. [Copyright &y& Elsevier]

The low cycle fatigue (LCF) property of welded joint is a key issue of fusion reactor blanket safety. In this study, LCF behavior of China low activation martensitic (CLAM) steel joint welded by electron beam was investigated under different strain amplitudes. The experimental results showed that the LCF life of the welded joint was lower than that of the base metal. Both the base metal and the welded joints exhibited continuous cyclic softening. However, the welded joint revealed a lower cyclic peak stress compared to that of the base metal. The welded joint failed in the welded zone at the strain amplitude of 0.3% and failed in the base metal at the strain amplitudes of 0.5%, 0.7% and 1.0%, respectively. The welding inclusion or defect in the surface could be the source of fatigue crack and the fatigue crack propagated in welded metal and heat affected zone with a transgranular fracture mode. [ABSTRACT FROM AUTHOR]