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Abstract: China Low Activation Martensitic (CLAM) steel is being developed at the Institute of Plasma Physics, Chinese Academy of Sciences under collaboration with many institutes and universities. This steel has been chosen as the primary candidate structural material for the LiPb blanket and DFLL–TBM developed in China. The development and testing strategy for DFLL–TBM includes three stages: out-of-pile tests, tests in EAST, and tests in ITER. The joining of CLAM by Hot Isostatic Pressing Diffusion Welding and Electron Beam Welding is being studied in detail, and small scale panels of the TBM first wall and cover plate with flow channels are being fabricated. Properties of CLAM including fatigue crack growth, creep properties and compatibility with liquid LiPb are also being studied. Recent progress in these R&D activities is summarized. [Copyright &y& Elsevier]

China Low Activation Martensitic (CLAM) steel is selected as the candidate structural material in Fusion Design Study (FDS) series fusion reactor conceptual designs. The creep property of CLAM steel has been studied in this paper. Creep tests have been carried out at 823 K and 873 K over a stress range of 150–230 MPa. The creep curves showed three creep regimes, primary creep, steady-state creep and tertiary creep. The relationship between minimum creep rate ( ε ̇ min ) and the applied stress ( σ ) could be described by Norton power law, and the stress exponent n was decreased with the increase of the creep temperature. The creep mechanism was analyzed with the fractographes of the rupture specimens which were examined by scanning electron microscopy (SEM). The coarsening of precipitates observed with transmission electron microscope (TEM) indicated the microstructural degradation after creep test. [ABSTRACT FROM AUTHOR]

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]

Abstract: To investigate the irradiation effects on a new version of reduced activation ferritic/martensitic steels (RAFMs) i.e. China Low Activation Martensitic steel (CLAM), neutron irradiation experiments has been being carried out under wide collaboration in China and overseas. In this paper, the mechanical properties of CLAM heats 0603A, 0408B, and 0408D were investigated before and after neutron irradiation to ∼0.02dpa at 250°C. The test results showed that ultimate strength and yield stress of CLAM HEAT 0603A increased about 10–30MPa and ductile to brittle transition temperature (DBTT) shift was about 5°C. For CLAM heats 0408B and 0408D, ultimate strength and yield stress increased about 80–150MPa. [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]

In this paper the microstructure and mechanical properties of electron beam weld (EBW) joints for China low activation martensitic (CLAM) steel, which underwent a series of different post weld heat treatments (PWHTs) were studied. The aim of the study was to identify suitable PWHTs that give a good balance between strength and toughness of the EBW joints. The microstructural analyses were performed by means of optical microscope (OM) and scanning electron microscope (SEM). The mechanical properties were determined via tensile tests and Charpy impact tests. The results showed that the tensile strength of the as-weld joint (i.e. without any PWHT) were close to that of the base metal, but the impact toughness was only 13% of that of the base metal due to the existence of a delta-ferrite microstructure. To achieve a significant improvement in toughness a PWHT needs to be performed. If a one-step PWHT is applied tempering at 760°C for 2h gives EBW joints with high strength at a still acceptable toughness level. If a two-step PWHT is applied, a process involving quenching at 980°C for 0.5h followed by tempering at 740°C or 760°C for 2h gives EBW joints with high strength and toughness properties. Whenever possible a two-step PWHT should be applied in favor of a one-step process, because of higher resulting strength and toughness properties. [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: In the design of liquid–metal fusion blankets, Al2O3 ceramic is one of the most promising coating materials. In this study, functionally graded FeAl/Al2O3 coatings were deposited on China Low Activation Martensitic (CLAM) steel substrates with vacuum plasma spraying (VPS) method. The SEM investigation revealed that the adhesion between adjacent layers in the coatings was sound. X-ray diffraction showed that stable alpha alumina dominated in the top alumina layers, while γ-Al2O3 and β-Al2O3 were also detected. The coating/substrate adhesive tensile strength test showed that adhesive strength of graded coatings was about 2.5 times that of duplex FeAl/Al2O3 coatings. Thermal shock resistance test indicated that the graded coatings could tolerate more thermal shock cycles than duplex coatings. [ABSTRACT FROM AUTHOR]

Abstract: Aluminum oxide Al2O3 coatings on China Low Activation Martensitic (CLAM) steel substrates were prepared with atmospheric plasma spray (APS) method. Corrosion experiments of the coating specimens in static liquid LiPb were carried out in DRAGON-ST capsule for 5000h at 550°C. The results showed that there is no obvious thinning of external layer Al2O3 after 5000h exposure. The γ phase Al2O3 in external layer and the dissolution of Ni in liquid LiPb from the edge of the internal layer Ni–Cr were the possible reasons for the corrosion of coatings. [ABSTRACT FROM AUTHOR]

Abstract: The first wall of the China dual functional lithium lead–test blanket module (DFLL–TBM) will be assembled with China low activation martensitic (CLAM) steel rectangular tubes and plates by hot isostatic pressing (HIP) – diffusion welding. The objective of this study is to evaluate CLAM rectangular tubes and investigate mechanical property and microstructure evolution of CLAM steel in tube fabrication and TBM assembly. In this work, CLAM rectangular tubes with lengths of 1500mm were fabricated, and the dimensional accuracy met the requirement for HIP joining. In the tube fabrication process, the CLAM steel was annealed to improve its ductility. In addition, the anisotropy in mechanical properties and microstructure introduced by tube rolling was eliminated according to the simulation of HIP heat treatment in TBM preparation. The tensile strength of the CLAM tubes with final heat treatment was slightly higher than that of CLAM steel with the published standard heat treatment, while the total elongation was reduced. This revealed that a post-HIP heat treatment was required before the final heat treatment. [Copyright &y& Elsevier]