A study on HAZ＇ s microstructure and grain size of 10CrNi3 MoV steel

This paper deals with microstructure and grain size of HAZ of 590 MPa high strength ship-structure steel with welding simulator. While t8/5 time is short, IOCrNi3MoV steel‘s microstructure of coarse grain heat-affected zone (CGHAZ) is lath martensite structure and a small amount of twined martensite structure; while t8/5 time is long, it is mainly granular bainite structure. After second thermal cycle with peak temperature between critical temperature Ac1‘ and Ac3‘ , CGHAZ has the inheritance of coarse grain and coarse rnicrostructure. Welding energy input ( determined by t8/5 time) has an effect on the inheritance of coarse microstructure, but no influence on‘the inheritance of coarse grain. In detail, with a shorter t8/5 time, there is an inheritance of coarse microstructure and grains. With a longer t8/5 time, there is only the inheritance of coarse grains. While t8/5 increases, the scope of temperature of causing it diminishes. Therefore, the inheritance of coarse microstructure connects with the high speed of heating and cooling.     

Effect of t8/5 on the microstructure and properties of the HAZ of ASME SA213-T92 steel by thermal simulation

The relationship between the t8/5 and micro-hardness, impact toughness in the heat affected zone （HAZ） of ASME SA213-792 at peak temperature of 1 350 ℃ was studied by thermal simulation. The result shows that the micro-hardness of HAZ rises at the beginning and then decreases with increasing of t8/5 , whereas the impact toughness presents reverse trend. The distribution of precipitates in substrate has great influence on the impact toughness of HAZ. When the t8/5 is 40 s, chain-like precipitates lower the impact toughness of HAZ seriously.     

The effects of metal binder content and carbide grain size on the aqueous corrosion behaviour of TiC–316L stainless steel cermets

The room temperature electrochemical response of TiC-based cermets, with 10 to 30 vol.% 316L stainless steel binder and either fine- or coarse-grained TiC, has been investigated in an aqueous 3.5 wt.% NaCl solution. The assessment methods included Tafel extrapolation, in combination with potentiodynamic and potentiostatic polarisation. Corroded samples were characterised using SEM, with post-corrosion solutions analysed using ICP-OES. The highest corrosion resistance was achieved at the lowest binder contents, while those with a more coarse-grained structure generally showed superior resistance, due to a reduced TiC–316L interfacial area. Preferential dissolution of the steel binder was observed, leaving the TiC essentially unaffected.     

Combination of TEM and 3D atom probe study of microstructure and alloy carbide in a Nb-V micro-alloyed steel tempered at 650 °C

3D atom probe (3DAP) combined with TEM is applied to characterize the nanostructure and composition of coarsening carbides that precipitate in a Nb-V micro-alloyed steel tempered at 650 °C for 4 h. The results indicate that high temperature tempering of the as-quenched lath-like martensitic structures leads to the coarsening of alloyed carbide in the recovered ferritic matrix. TEM characterization and EDS analysis show that the alloy carbides are typically spherical or ellipsoidal and are enriched with V, Nb and Mo. Crystallographic lattice overlap and distortion create a distinct optical Moiré pattern at the carbide/matrix boundary, as observed by HRTEM. 3DAP gives the compositional distribution at atomic scale in the coarsening carbide and the surrounding matrix. Non-carbide-forming elements such as Si and Al are depleted in the carbide and are enriched at the carbide/matrix heterophase interface. Carbide-forming elements such as Mn, V, Mo and Nb distribute heterogeneously in the whole carbide, leading to the formation of a Mn-, V- and Mo-enriched core and Mo-enriched external shell.     

Effect of grain size and partial disordering on ductility of Ti3Al in the temperature range of 20–600°C

The effect of grain size and partial disordering on ductility and flow stress of an intermetallic Ti₃Al was studied in the temperature range of 20–600°C using tension and compression testing. The ductility of the fully ordered material increased considerably when the grain size decreased from 27 to 0.1 μm, and, at the smaller grain size, an elongation of 4.8% was achieved at room temperature. Partial disordering of the crystal lattice led to a decrease in ductility at temperatures below 500°C, but had no influence on the ductility at 500 or 600°C. The critical grain size at which a brittle-to-ductile transition occurred in the fully ordered material was determined for each temperature studied. This critical grain size increased as the temperature was increased. It was found that, when the mean grain size decreased and temperature increased, the fracture mode changed from a brittle transcrystalline mode to a brittle intercrystalline mode and, finally, to a ductile transgranular mode. The increased ductility was correlated with an enhanced grain boundary relaxation capability at increased temperatures and decreased grain sizes.     

The effects of triple junctions and grain boundaries on hardness and Young’s modulus in nanostructured Ni–P

Hardness and Young’s modulus were measured on a series of nanocrystalline Ni–P samples. With decreasing grain size, a transition from regular to inverse Hall–Petch relationship and a reduction in Young’s modulus at the smallest grain sizes was observed, which can be attributed to grain boundary and triple junction effect.     

An X-ray photo-electron spectroscopic study of the films on coloured stainless steel and coloured ‘Nilomag’ alloy 771

X-ray photo-electron spectroscopy (XPS) studies have been made on the decorative films produced on stainless steel and on ‘Nilomag’ alloy 771. The films were produced by immersing the samples in 2.5 mol dm^?3 chromic acid/5.0 mol dm^?3 sulphuric acid solution at 70°C, a process developed commercially by International Nickel Ltd. These studies show that the film on stainless steel is composed principally of iron, chromium and oxygen and the species present in the film are invariant with thickness. The film on the ‘Nilomag’ 771 is principally composed of iron, nickel, chromium, molybdenum and oxygen. The presence of chromium in the latter film suggsets that the chromic acid takes part in the film formation reaction.     

Research on the creep damage and interfacial failure of dissimilarmetal welded joint between 10Cr9Mo1 VNbN and 12Cr1MoV steel

0　IntroductionAnewmodified 9Cr Mosteel (SA2 13T91orT91)pos sessesimprovedhightemperaturestrength ,excellentductili ty ,weldability ,heatfatigueproperties .Therefore ,T91hasbeenwidelyusedinelectricpower,petrochemicalplant,nu clearpowerstation ,andsoon[1～3] .Itisappliedtothefinalstagesofsuperheatersandreheatersinfossil firedpowerplants .However,lowalloypearlitesteel(12Cr1MoV)isstillusedintheearlierstages .Thus,therearealotofdissimilarmetalweldedjoints (DMWJs)betweenSA2 13T91and12Cr1Mo…     

Effect of anisotropy on microstructure and high temperature stress rupture properties of Ni3A1 base single crystal alloy

The effect of anisotropy on microstructure and high temperature stress rupture property of Ni3A1 base single crystal alloy was investigated. The single crystal specimens were produced by screw selection crystal method. The microstructures were examined by OM, SEM, TEM and X-ray EDS techniques. The stress rupture tests were can-led out in air by constant load creep machines under 1 100 ℃ and 130 MPa. The experimental results show that the dendrites preferential orientation deviates certain angles to heat flow orientation, and the secondary arms occur for different crystallographic orientations. The single crystal alloy with different orientations shows obvious anisotropy during tensile stress rupture tests under 1 100 ℃ and 130 MPa. The 〈111〉 orientation specimen has the best stress rupture life of 211 h. The high ductility at 1 100 ℃ of the 〈001〉 orientation specimen may be attributed to the most multiple equivalent slip systems.     

Influence of Yb2O3 addition on microstructure and corrosion resistance of 10Cu/（10NiO-NiFe2O4） cermets

10Cu/(10NiO-NiFe₂O₄) cermets doped with Yb₂O₃ were prepared by conventional powder metallurgy technique. The effects of Yb₂O₃ content and sintering temperature on the relative density, phase composition, microstructure of the sintered cermets and the corrosion resistance to Na₃AlF₆-Al₂O₃ melts were investigated by sintered density test, XRD analysis and SEM. YbFeO₃ phase, which distributes in the ceramics grain boundary as particles or film, is produced by the reaction between Yb₂O₃ and ceramics. The addition of Yb₂O₃ accelerates the sintering process of ceramics matrix, eliminates pores in the boundary and results in coarsened crystalline grain. The relative density of the cermets with about 1% (mass fraction) Yb₂O₃ sintered at 1275 °C increases to above 95%. Addition of about 1.0% Yb₂O₃ can inhibit obviously the corrosion of NiFe₂O₄ grain boundary and Cu phase in Na₃AlF₆-Al₂O₃ melts.     

Effect of high temperature aging on microstructure and mechanical properties of a directionally solidified Ni3Al base alloy IC6A

1　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｄｉｒｅｃｔｉｏｎａｌｌｙｓｏｌｉｄｉｆｉｅｄＮｉ3ＡｌｂａｓｅａｌｌｏｙＩＣ6ＡｗｉｔｈｔｈｅｃｈｅｍｉｃａｌｃｏｍｐｏｓｉｔｉｏｎｏｆＮｉ (7.5～8.5 )Ａｌ (13.0～ 15 .0 )Ｍｏ (0 .0 2～ 0 .1)Ｂ (0 .0 0 5～0 .0 5 )Ｙ (ｍａｓｓｆｒａｃｔｉｏｎ ,% )ｈａｓｂｅｅｎｒｅｃｅｎｔｌｙｄｅｖｅｌ ｏｐｅｄｂａｓｅｄｏｎａｌｌｏｙＩＣ6ａｓａｈｉｇｈ ｔｅｍｐｅｒａｔｕｒｅｓｔｒｕｃ ｔｕｒａｌｍａｔｅｒｉａｌｕｓｅｄｆｏｒａｄｖａｎｃｅｄｊｅｔ ｅｎｇｉｎｅｖａｎｅｓｏｐ ｅｒ…     

A comparative ab initio study of the ‘ideal’ strength of single crystal α- and β-Si3N4

In this study, the ideal tensile and shear strengths of single crystal α- and β-Si₃N₄ were calculated using an ab initio density functional technique. The stress–strain curve of the silicon nitride polymorph was calculated from simulations of predefined strain deformation in various directions. In particular, the ideal strength calculated for an applied tensile γ₁₁ strain, in the [1 0 0] plane, was estimated to be ∼51 and 57 GPa, for α- and β-Si₃N₄, respectively. Using a reported empirical method an estimate was also made of the Vickers indentation hardness of the α- and β-Si₃N₄ single crystals, ∼23.0 and 20.4 GPa, respectively. Moreover, a hardness estimate has been reported for Si₃N₄ in the literature: ∼21.0 GPa.     

Investigation of the effect of Al2O3–Y2O3–CaO (AYC) additives on sinterability,microstructure and mechanical properties of SiC matrix composites: A review

Appropriate properties of SiC ceramic such as high hardness, low density, high melting point and high elastic modulus make this material as a favorite candidate for different industrial applications. Although some disadvantages including high sintering temperature, low sinterability, and low fracture toughness have restricted the use of this material, previous studies showed that using Al₂O₃-Y₂O₃ additives plays an effective role in the improvement of sinterability as well as the enhancement of the properties of these composites. Moreover, the addition of CaO results in the acceleration of the formation of molten phase and the improvement of sinterability. In addition, the use of these additives cause the formation of the intermetallic phases of Al₅Y₃O₁₂ (YAG) and CaY₂O₄ and by activating the mechanisms of crack deflection, crack bridging, phase transformation, strengthening the grain boundary and changing the fracture mode from intergranular to transgranular results in improved mechanical properties. This paper attempts to investigate the effect of using Al₂O₃–Y₂O₃–CaO (AYC) additives on sinterability, microstructure, and mechanical properties of SiC matrix composites including the composites reinforced with SiC fibers and SiC matrix nano-composites. Finally, the effect of the post-sintering annealing process under two conditions i.e., with and without applying pressure (pressureless sintering) on microstructure and mechanical properties has been studied.     

A study on the influence of the sloped cutting angle on kerfwidth and part quality in the hotwire cutting of EPS foam for the VLM- rapid prototyping process

The VLM- rapid prototyping process employs hotwire cutting of an EPS foam sheet using a four-axis synchronized automatic hotwire cutter. The dimensional accuracy and the quality of the cut part are highly dependent on cutting parameters such as effective heat input, and cutting angle, etc. The objective of this study is to investigate the influence of cutting angle on the kerfwidth and the part quality in hotwire cutting of EPS foam for the case of the sloped cutting including single-sloped cutting with one cutting angle and generally sloped cutting with two cutting angles. Experiments are carried out to obtain the relationship between kerfwidth and effective heat input for each cutting angle, and to find the relationship between the melted area and the cutting angle for each effective heat input. In order to investigate the influence of cutting angle on temperature distribution in EPS foam, transient heat transfer analysis using the sloped heat flux model and the conformed mesh structure is carried out. Through comparison of the results of the experiment and the transient heat transfer analysis, it has been shown that the sloped heat flux with an elliptical cross-section and the conformed mesh structure are needed to estimate the three-dimensional temperature distribution in the EPS foam in the sloped hotwire cutting.