Diffusional stability of ferritic–martensitic steel composite for service in advanced lead–bismuth cooled nuclear reactors

Abstract

To combat liquid metal corrosion from lead–bismuth eutectic coolant in the fuel cladding and coolant piping of generation IV fast fission reactors, a composite that employs a Fe–Cr–Si steel layer weld clad on a structural layer of alloy T91 (Fe–9Cr–1Mo) is being developed. Diffusion of Si away from the cladding during service can compromise corrosion resistance, whereas carbon redistribution will affect mechanical properties and phase stability. Diffusion of silicon and carbon in a manufactured sample of the composite has been investigated both experimentally and by modelling. The diffusion coefficient for silicon in the T91/Fe–12Cr–2Si system was found to be 1·36 × 10^?12 cm² s^?1 at 650°C, implying that concentration in the clad layer should not drop below 1·25%Si at a distance of 51 μm from the interface after 50 years' service at 650°C. The rapid carbon diffusion observed should be helpful during processing and operation. The two layers will have similar properties once carbon diffuses into the cladding, reducing the probability of mechanical property mismatch based errors during processing. The increased hardness of the carbon enriched clad layer will result in higher strength during operation, reducing the likelihood of damage or abrasion.     

Surface Modification of Polymer Films for Improved Adhesion of Deposited Metal Layers

Plasma treatment and vacuum Al deposition on films from biaxially oriented polypropylene is a multistep large scale industrial process, mainly ending up in packaging film laminates. As atmospheric plasma treatment processes suffer from lack of reproducibility, low pressure plasma treatment processes that can be operated in-line with the metal deposition are being developed. Process development is difficult, because the final packaging film laminate has to deliver optimum properties of adhesion as well as of the barrier against oxygen and water vapor permeation. As a typical production run involves tens of thousands to up to one hundred thousand square meters of film, experiments on an industrial scale are expensive, so smaller scale experimental processes are needed, which so far do not match well enough with industrial process characteristics. Moreover, bonding mechanisms between the treated substrate film and the deposited Al layer are not sufficiently understood. This paper describes the sequence in development and optimization of substrate films and plasma treatment that has been performed on an experimental as well as on an industrial scale. A sufficient correlation between experimental and industrial scales was achieved, which helps to perform development and optimization on a small scale before scaling up to industrial processes. However, improvement is still needed both in fundamental understanding of the aluminum–polypropylene interface as well as in experimental equipment and methodology.     

Multilayer Metal Film Plating on Glass

It has been shown that an under-layer of SiO₂ · nH₂O on a silicate glass surface, promotes the adsorption of Sn(II) hydroxycompounds, resulting in the formation of Sn–O–Si chemical bonds. It also: contributes to the formation of monodispersed Sn(II) compound nanoparticles; levels the glass surface micro-relief; ensures the deposition of fine-grained metal films; increases the rate of Ni–P and Cu electroless plating; and increases the rate of the adhesion interaction between the surface of the silicate glass and metal films. It opens up the possibility of electroless and electrochemical plating of 5–10 μm thick multilayer metal and alloy films.     

New stability index for short circuit transfer mode in GMAW process using acoustic emission signals

Abstract

A new index for the analysis of stability of GMAW processes taking as a base the acoustic emission generated by the arc during the short circuit metal transfer is presented in the present work. The incidence of parameters of process is analysed in the indices of the acoustic emission signal, as well as its influence on the stability, evaluated through a new proposed index. The results obtained allowed having a relationship between acoustic signals and arc voltage signals, and demonstrated the validity of proposed index of acoustic emission for analysis of stability of GMAW process. The obtained results were then compared with other classic stability analysis methods based on statistical analysis of temporal signals of arc voltage. Finally a statistical analysis for the validation of the obtained experimental results was carried out. As a result of the investigation, the effectiveness of the method proposed as a new way for the analysis of stability is demonstrated. The research can contribute towards a new standard to evaluate the stability in welding processes.     

Material and processing behaviour of thermoplastics filled with low melting metals

Abstract

Polymer blends filled with solid fillers such as metal fibres or carbon black can no longer fulfil the increasing demands on electrical and thermal conductivity. High levels of hard fillers increase the melt viscosity unacceptably, causing a minimised process window, high mechanical stresses on the polymer as well as an increased abrasion on both mould and machinery. The high electrical conductivity required for connectors, moulded interconnect devices or sensors can be achieved by a novel material developed by IKV, Aachen, and Siemens AG, Erlangen/Germany. It combines fibre filled polymer blends with low melting metal alloys. These alloys have the advantage of being already molten during processing and of not solidifying before the cooling phase. The result is a free flowing material that allows the injection moulding of complex geometries. A passage conductivity of the moulded parts in the range of pure metals can be achieved.     

FINITE ELEMENT NUMERICAL SIMULATION OF TEMPERATURE FIELD IN METAL PATTERN CASTING SYSTEM AND ＂REVERSE METHOD＂ OF DEFINING THE THERMAL PHYSICAL COEFFICIENT

With the technology support of virtual reality and ANSYS software, an example on the simulation of temperature distribution of casting system during the solidification process was provided, which took the latent heat of phase change, the conditions for convection, and the interface heat transfer coefficient into consideration. The result of ANSYS was found to agree well with the test data. This research offers an unorthodox way or "reverse method" of defining the relevant thermal physical coefficient.     

Ab initio Studies on Magnetism of 3d Transition Metal Dimers

Ab initio calculations with the self-consistent full-potential linearized augmented-plane-wave method (FLAPW), under generalized gradient approximation, have been carried out to describe the electronic and magnetic properties of 3d transition metal dimers. It predicted the antiferromagneticity of Cr2 and ferromagneticity of other species. The Mn2 dimer was shown to be ferromagnetic coupling with a local magnetic moment of 5μB, retaining the value of its free atom state. The V2 and Ni2 exhibited low spin-polarization with local magnetic moment of only 1μB per atom. On the other hand, Fe2 and Co2 were highly spin-polarized with local magnetic moments of 3 and 2μB.     

Temperature dependence of low cycle fatigue of 316(N) weld metals and 316L(N)/316(N) weld joints

Abstract

The low cycle fatigue behaviour of 316(N) weld metals and 316L(N)/316(N) weld joints have been investigated in the temperature range of 300–873 K, at a strain amplitude of ±0·6% and a strain rate 3 6 10^–3 s^–1, to study the influence of dynamic strain aging (DSA). The 316(N) weld metal exhibited better fatigue life than the weld joint, though the weld metal has shown higher cyclic stress response and higher plastic strain accumulation than the weld joint. Significant features observed in the temperature regime of 300–873 K include the maximum in fatigue life at 573 K and DSA in the range of 673–873 K. Occurrence of DSA has been manifested through drastic reduction in fatigue life in the range of 673–873 K, associated with anomalous stress response. Dominant DSA effects have been observed at about 773 K in the weld joint and at 823 K in the weld metal. However, the effect of DSA is found to be nominal beyond 823 K where the reduction in fatigue life is attributed to the combined effects of oxidation and DSA. Secondary crack density measurements (in the range of 300–873 K) in the weld joint specimens revealed the severity of the heat affected zone (HAZ) in inducing fatigue damage. Parameters have been identified to determine the temperature corresponding to dominant DSA effects.     

Residual stresses and practical adhesion: effect of organo-metallic complex formation and crystallization

Epoxy-amine liquid pre-polymers are often applied onto metallic substrates and cured to obtain painted materials or bonded joint structures. The overall performance of such systems depends on the interphase created between the epoxy-amine polymer and the metallic substrate. When epoxy-amine liquid mixtures are applied onto a metallic oxide layer, concomitant amine chemisorption and oxide dissolution occur leading to organo-metallic complex formation. Depending on the amine nature, as soon as the organo-metallic complex concentration is higher than the solubility product (e.g., isophoronediamine (IPDA)), these organo-metallic complexes crystallize as sharp needles. At the same time, the uncrystallized organo-metallic complexes react with the epoxy monomer to form, after curing cycle, a new network. Moreover, the crystal size increases with the solid/liquid contact time leading to an increase of intrinsic residual stresses and Young's modulus. When aliphatic diethylenetriamine (DETA) was used, no crystallization occurred, but the interphase formation was observed. The aim of this study was to understand and to establish the role of crystallization of organo-metallic complexes formed within the interphase on the practical adhesion performance. As the crystallization of the organo-metallic complex depends on the nature of the amine, two amine hardeners were used (IPDA inducing the formation of crystals and DETA without formation of crystals). For DGEBA-IPDA systems, the ultimate load decreases while residual stresses increase when the liquid/solid contact time increases. When no crystal formation was observed (e.g., DGEBA-DETA system), residual stresses, coating Young's modulus and ultimate load values all remained nearly constant irrespective of the liquid/solid contact time.     

The Static Failure of Adhesively Bonded Metal Laminate Structures: A Cohesive Zone Approach

Adhesively bonded metal laminates are used in aerospace applications to achieve low cost, light weight structures in the aerospace industry. Advanced structural adhesives are used to bond metal laminae to manufacture laminates, and to bond stringers to metal laminate skins. Understanding the failure behaviour of such bonded structures is important in order to provide optimal aircraft designs. In this paper, the static failure behaviour of adhesively bonded metal laminate joints is presented. A cohesive zone model was developed to predict their static failure behaviour. A traction–separation response was used for the adhesive material. Three joint configurations were considered: a doubler in bending, a doubler in tension and a laminated single lap. The backface strains and static failure loads obtained from experimental tests were used to validate the results from finite element modelling. The models were found to be in good agreement with experiments.