THE INTERFACE OF TERNARY-BORIDE-BASED HARD CLADDING MATERIAL

The interfacial microstructure of ternary-boride-based hard cladding material (YF-2) has been studied using scanning electron microanalyser (SEM), X-ray diffraction (XRD) and energy disperse spectroscopy (EDS). Results show that there are chemical reactions and elements diffusion in the interfacial zone, which make the interface bonding well and bonding strength ideal at the interface. The results gotten by studying of crack produced by Vickers indentation technique in the interfacial zone show that it is difficult to produce crack in the interface, the crack length in the cladding layer is longer than that to the interface, the crack which propagate to the interface stops at the interface rather than propagates along the interface. This suggests negligible residual stresses have developed because of thermal expansion mismatch. The bonding strength of the interface is 550MPa, which has been gotten by cutting test. The result gotten by analyzing the fracture surface shows that the fracture occurs at the side of cladding layer, which confirms that the bonding strength at the interface is higher than that in the cladding layer.

Effects of Fe-Al intermetallic compounds on interfacial bonding of clad materials

The growth of intermetallic compounds at the interface between solid Al and Fe and the effects of intermetallic compound layers on the interfacial bonding of clad materials were investigated. The results showed that the interface between the solid Fe and Al formed by heat-treatment consisted of Fe2Al5 and FeAl3 intermetallic compound layers, which deteriorated the interfacial bonding strength. Fractures occurred in the intermetallic compound layer during the shear testing. The location of the fracture depended on the defects of microcracks or voids in the intermetallic compound layers. The microcracks in the intermetallic compound layer were caused by the mismatch of thermal expansion coefficients of materials during cooling, and the voids were consistent with the Kirkendall effect. The work will lay an important foundation for welding and joining of aluminum and steel, especially for fabrication of Al-Fe clad materials.

Corrosion of candidate materials for supercritical water-cooled reactor

Supercritical water reactor(SCWR) was proposed as a GenerationⅣconcept for building large capacity nuclear power plants.Comparing with the present GenerationⅡandⅢlight water reactors,SCWR possesses great advantages of 10%higher efficiency,simpler system design,better sustainability,and so on. However,the selection of materials for fuel cladding and reactor internals of SCWR is facing a great challenge. Corrosion in supercritical steam is of the first important issue to be solved to meet the stringent requirement of the reactor internal components.Corrosion screening tests were conducted on candidate materials for nuclear fuel cladding and reactor internals of supercritical water reactor(SCWR) in static and re-circulating autoclave at the temperatures of 550,600 and 650℃,pressure of about 25 MPa,deaerated or saturated dissolved hydrogen(STP). Nickel base alloy type Hastelloy C276,austenitic stainless steels type 304NG,AL-6XN,HR3C.NF709 and SAVE 25,ferritic/martensitic(F/M) steel type P92,P122 and 410,and oxide dispersion strengthened steel MA 956,are tested.This paper presents corrosion rate,and focuses on the formation and breakdown of corrosion oxide film,and proposes the future trend for the development of SCWR internal structure materials.

Current state and prospect on the development of advanced nuclear fuel system materials:A review

The intricate balance between reactor economics and safety necessitates the emergence of new and advanced nuclear systems and,very importantly,advanced materials,which can overcome current shortcomings and bring about more economic nuclear systems with designed-in inherent safety features.These advances will achieve greater safety and better nuclear reactor economics by reaching longer reactor lives with higher levels neutron irradiation,and by providing higher operation temperatures and resistance to more aggressive corrosive environments.This paper provides a review of the current state of research and development on innovative nuclear fuel materials design and development which have the potential of benefiting simultaneously reactor economics and safety.Our discussion focuses on three areas of research:Accident-tolerant Fuels(ATFs),Oxidation Dispersion Strengthened(ODS)steels and High Entropy Alloys(HEAs).The paper also gives a prospective description of future research activities on these materials.

Effect of hydro co-extrusion on microstructure of duo-cast Al3003/Al4004 clad materials

The effects of hydro co-extrusion on the microstructure changes of aluminum hybrid duo-cast Al 3003/Al 4004 clad materials were studied. The specimen of duo-cast Al 3003/Al 4004 clad materials was in circle shape, and was composed of Al 3003(outside) and Al 4004(inside) materials. The specimen was extruded by the hydro co-extrusion equipment. The manufacturing conditions of the specimen were 423 K in temperature and 5 in extrusion ratio. The dimensions of the specimen were 80 mm in diameter of the Al 4004 material and 35 mm in thickness of the Al 3003 material before the hydro co-extrusion process, and 30 mm in diameter and about 5 mm in thickness after the extrusion process, respectively. The microstructure and the hardness for two specimens were investigated. The hardness value of cross section in the duo-cast Al 3003/Al 4004 clad materials before the extrusion process was increased in form of the parabola toward the center. However, after the extrusion process, it was almost constant in the portion of Al 4004 material. Lots of big voids above 1 mm in diameter in the specimen existed in the interfacing region of Al 3003 and Al 4004 materials before the extrusion process. These big voids disappeared after the process of hydro co-extrusion.

Fabrication of Fe–TiC–Al_2O_3 composites on the surface of steel using a TiO_2–Al–C–Fe combustion reaction induced by gas tungsten arc cladding

The aim of the present study was to fabricate Fe-TiC-Al2O3 composites on the surface of medium carbon steel.For this purpose,TiO2-3C and 3TiO2-4Al-3C-xFe（0 ≤ x ≤ 4.6 by mole） mixtures were pre-placed on the surface of a medium carbon steel plate.The mixtures and substrate were then melted using a gas tungsten arc cladding process.The results show that the martensite forms in the layer produced by the TiO2-3C mixture.However,ferrite-Fe3C-TiC phases are the main phases in the microstructure of the clad layer produced by the 3TiO2-4Al-3C mixture.The addition of Fe to the TiO2-4Al-3C reactants with the content from 0 to 20wt%increases the volume fraction of particles,and a composite containing approximately 9vol%TiC and A12O3 particles forms.This composite substantially improves the substrate hardness.The mechanism by which Fe particles enhance the TiC ＋ A12O3 volume fraction in the composite is determined.

Development of Glass Optical Fibers 1970-2020,Providing Us the Digitalized Communication World

New types of communication cables were found to be needed already during the 1960-decade,because the copper cables had,and still would have,too high attenuation and especially limited bandwidth,due to extremely high dispersion at communication signals above 2 Mbit/s.Already the first commercially available multimode optical fibers(1979),developed from pure silica glass with a Ge-doped core,had much lower attenuation at signal frequencies of the order of 2-9 Mbit/s and above it.However,fiber core,cladding and coating materials,cable structures and materials,as well as manufacturing-,measurements-and test methods have been needed to be developed much further to get the reliable fiber cable communication networks.The important development stages and solutions to the most significant childhood problems of the optical fibers and cables are described in this paper.Now over 500 million km of optical fibers are manufactured and installed worldwide for the communication networks.The understanding of how to make the fibers with the very good transmission,mechanical and reliability properties exists at the manufacturers of the fibers and cables.

Interfacial phase formation of Al-Cu bimetal by solid-liquid casting method

The solid-liquid method was used to prepare the continuous casting of copper cladding aluminium by liquid aluminum alloy and solid copper, and the interfacial phase formation of Al-Cu bimetal at different pouring temperatures(700, 750, 800 oC) was investigated by means of metallograph, scanning electron microscopy(SEM) and energy dispersive spectrometry(EDS) methods. The results showed that the pouring temperature of aluminum melt had an important influence on the element diffusion of Cu from the solid Cu to Al alloy melt and the reactions between Al and Cu, as well as the morphology of the Al-Cu interface. When the pouring temperature was 800 oC, there were abundant Al-Cu intermetallic compounds(IMCs) near the interface. However, a lower pouring temperature(700 oC) resulted in the formation of cavities which was detrimental to the bonding and mechanical properties. Under the conditions in this study, the good metallurgical bonding of Al-Cu was achieved at a pouring temperature of 750 oC.

In situ synthesis of Fe-based alloy clad coatings containing TiB_2–TiN –(h-BN)

Fe-based alloy coatings containing TiB2–TiN –（h-BN） were synthesized in situ on Q235 steel substrates by a plasma cladding process using the powders of Fe901 alloy, Ti, and h-BN as raw materials. The effects of Ti/h-BN mass ratio on interfacial bonds between the coating and substrate along with the microstructures and microhardnesses of the coatings were investigated. The results show that the Ti/h-BN mass ratio is a vital factor in the formation of the coatings. Free h-BN can be introduced into the coatings by adding an excess amount of h-BN into the precursor. Decreases in the Ti/h-BN mass ratio improve the microstructural uniformity and compactness and enhance the interfacial bonds of the coatings. At a Ti/h-BN mass ratio of 10/20, the coating is free of cracks and micropores, and mainly consists of Fe-Cr, Fe3B, TiB2, TiN, Ti2N, TiB, FeN, FeB, Fe2B, and h-BN phases. Its average microhardness in the zone between 0.1–2.8 mm from the coating surface is about Hv0.2 551.5.

Al 1060/Pure Iron Clad Materials by Vacuum Roll Bonding and Their Solderability

Al 1060/pure iron clad materials were produced by vacuum roll bonding. The effects of preheating temperature, vacuum roll reduction and initial thickness of the A11060 sheet on the metal interface and bonding strength were investigated. The interfacial microstructure was investigated and the mechanical properties of the joint were evaluated by shear testing. The bonding strength of the clad materials was generally enhanced by increasing the total reduction or preheating temperature, which caused the metal interface to flatten. No obvious reaction or diffusion layer was observed at the interface between Al 1060 and pure iron. The bonding strength increased with decreasing the initial thickness of the Al 1060 sheets. The Al 1060/pure iron clad materials were soldered with Zn-Al alloy by using an ultrasonic-assisted method. Strong bonding of the Al 1060 layer and Al 7N01 was realized without obvious Al 1060 dissolution or effect on the initial interface of Al 1060/pure iron clad materials by soldering at relatively low temperature.

Effect of Heat Treatment Process on Mechanical Properties and Microstructure of Modified CNS-ⅡF/M Steel

Ferritic/martensitic（F/M） steels have been recommended as one of the candidate materials for supercritical water cooled reactor（SCWR） in-core components use for its high thermal conductivity,low thermal expansion coefficient and inherently good dimensional stability under irradiation condition in comparison to austenitic steel.CNS-Ⅱ F/M steel which has good mechanical properties was one of the 9-12Cr F/M steels designed for SCWR in the previous work.In this study a modified CNS-Ⅱ F/M steel was used and it＇s ultimate tensile strength was 925 MPa at room temperature and 483 MPa at 600 ℃ after optimizing heat treatment parameter.The ductile to brittle transition temperature of modified CNS-Ⅱ F/M steel is-55 ℃.Those are at the same level or even higher than that of CNS-Ⅱ and some commercial F/M steels nominated for SCWR in-core component use.The transmission electron microscope（TEM） results showed that the mechanical properties of the tempered martensite was closely related to the decomposition stage of the martensite.