Microcalorimetric measurements in Fe-C and Fe-C-Si-Mn alloys

Microcalorimetric measurements of heat related to fusion and crystallization of the eutectic in Fe-C and Fe-C-Si-Mn alloys have been carried out. In the case of Fe-C alloys, the heat related to fusion and crystallization of the eutectic changed from 0 to 215 kJ/kg and from 0 to 207 kJ/kg, respectively. For Fe-C-Si-Mn alloys, the heat related to fusion and crystallization of the eutectic changed from 178 to 220 kJ/kg and from 169 kJ/kg to 216 kJ/kg, respectively. This was attributed to the change of the content of eutectic in the alloys.     

Prediction of Heat of Fusion of Rare Earth Compounds from Binary Phase Diagrams

Based on the thermodynamical principle the new formula for calculation of heat of fusion and its error havebeen derived from binary phase diagrams which could be classified to eutectic,solid solution,degenerate eutecticand involving a compound phase diagram and so on.Using these formulae heats of fusion of some rare earth ox-ides have been predicted.     

Susceptibility of iron castings to heat absorption from an electric arc and to hardened-layer shaping

Surface fusions were performed by the gas tungsten arc welding (GTAW) surfacing process on plate castings of spheroidal graphite cast iron with a travel speed from 200 to 800 mm/min. Their geometry and hardness were measured. Calorimetric measurements of the net heat input for the GTAW process have been conducted. A stepwise regression method was used to develop the relationship between GTAW process parameters and those of fusion geometry, microhardness, arc efficiency, and melting efficiency for the obtained data set.     

Modeling of fixed bed heat storage units utilizing phase change materials

A computer model has been developed for the calculation of the heat exchanged and temperature profiles in a packed bed containing a phase change material. The packed bed is intended as a heat storage unit in which an inert fluid flowing through the bed exchanges heat with an encapsulated spherical shot of the phase change (melting and freezing) material. Examples of predicted bed temperature profiles during heat storage and utilization cycles are given. For A1-12 wt pct Si and Al-30 wt pct Si shot, a sequence of storage and utilization cycles with cyclic cocurrent fluid flow was found to utilize the high latent heat of fusion of the shot efficiently and permit the utilization of the bed as a near isothermal (577°C) heat recuperator.     

Weld microstructure of (Ni,Fe)3(V,Ti) long-range-ordered alloy

The microstructure of gas tungsten arc (GTA) welds of a (Ni, Fe)₃ (V, Ti) long-range-ordered alloy has been investigated. Crack-free welds were produced in which the heat affected zone (HAZ) and fusion zone were disordered and softened. A post-weld heat treatment increased the hardness of both zones by reordering the structure. The reordering treatment produced additional hardening in the fusion zone due to precipitation of small VC particles on grain boundaries and matrix dislocations.     

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Electro-slag welding with heat input of 530kJ/cm was applied to 60mm thick shipbuilding plate EH40, and microstructure and mechanical properties of the weld joint were characterized. Different regions such as heat affected zone, fusion zone, weld metal and base metal are found across the weld joint by microstructure analysis. A narrow coarse grain heat affected zone consisting of acicular ferrite, polygonal ferrite and grain boundary ferrite is found, width of which is less than 1mm. Acicular ferrite (?? 10??m) and grain boundary ferrite is observed at weld metal, while fusion zone have a complex structure of acicular ferrite, grain boundary ferrite and ferrite side plate. Mechanical property tests show that the absorbed energy of WM, FL and CGHAZ at -20?? during Charpy impact test is more than 60J, no evident softening phenomenon occurred at heat affected zone, and other properties met the requirement.     

Weldability and Microstructure of Nickel-Silicon Based Alloys

The NiSix based alloy typically has poor weldability due to its lower ductility. A limited amount of work has been performed on the weldability of NiSix based alloys. Therefore, the effect of heat treatment and welding parameters on weldability of the alloys, and the relationship between the weldability and microstructure were studied. The results show that the as-cast Ni-Si-Nb-B alloy （Ni 76. 5%, Si 20%, Nb 3%, and B 0. 5%） could be successfully welded after preheating at 600 ℃. The welding procedure should be performed on the alloys before any heat treatment and a preheating at 600 ℃ should be used. The fusion zone is harder than the matrix due to a large amount of 7 phase and a finer microstructure. The cracks are predominantly intergranular in heat affected zone and associated with the needle-like ）, phase. The heat treatment before welding increases the tendency of cracking in the fusion zone.     

Basal metabolism of intraperitoneally injected carrier-free 74As-labeled arsenate in rabbits

A streptavidin-RNase H gene fusion was constructed by cloning the Thermus thermophilus RNase H coding sequence in the streptavidin expression vector pTSA18F. The gene was expressed in Escherichia coli, and the resulting fusion protein was purified to apparent homogeneity. The fusion protein was shown to have a molecular weight of 128 kDa and to consist of four subunits. Furthermore, heat treatment of the fusion enzyme showed that it was stable as a tetramer at 65 degrees C. The fusion enzyme was shown to have both biotin binding and RNase H catalytic properties. Using cycling probe technology (CPT), the fusion enzyme was compared to the native RNase H with a biotinylated probe at different ratios of probe:enzyme and varying amounts of synthetic target DNA. At a ratio of 1:1, the fusion enzyme was active in CPT, but the native enzyme was not; both enzymes were active at a 1:5000 ratio of probe:enzyme. The fusion enzyme was further tested using biotinylated and non-biotinylated probes and was shown to be active at a 1:1 ratio with the biotinylated probe but not with the non-biotinylated probe. These experiments show that through binding of the streptavidin-RNase H fusion enzyme to the biotinylated probe, the efficiency of the cycling probe reaction is enhanced.     

粉末床熔融成形铜及铜铬系合金研究进展

近年来,越来越多的研究报道了粉末床熔融成形技术。这一技术通过热源扫描熔化粉末,逐层堆积直接成形复杂三维金属零件结构,能够极大地缩短产品生产周期,提高生产效率,特别是在选区激光熔化（SLM）以及选区电子束熔化（SEBM）制备铜及铜铬系合金方面取得了很大的突破。本文综述了粉末床熔融成形技术的基本原理和优势,以及在增材制造（AM）技术中,铜系材料打印存在的主要困难。介绍了不同制备方法对材料性能的影响,重点对比了SLM工艺在铜系金属上的高反射率问题,进而阐明提高铜对激光的吸收率是该成形技术的研究重点,以及SEBM工艺在铜系金属中存在的表面粗糙度问题的重要性。探讨了更为前沿的一种电子束-激光符合选区融化（EB-LHM）技术,虽然其工艺更复杂但能结合不同打印方法提升性能。探讨了不同成形工艺对材料微观结构和力学性能的影响,并对材料的打印方式进行了评价。最后对目前该领域存在的问题和未来的研究方向进行了展望。     

Numerical simulation of three-dimensional heat transfer and plastic flow during friction stir welding

Three-dimensional visco-plastic flow of metals and the temperature fields in friction stir welding have been modeled based on the previous work on thermomechanical processing of metals. The equations of conservation of mass, momentum, and energy were solved in three dimensions using spatially variable thermophysical properties and non-Newtonian viscosity. The framework for the numerical solution of fluid flow and heat transfer was adapted from decades of previous work in fusion welding. Non-Newtonian viscosity for the metal flow was calculated considering strain rate, temperature, and temperature-dependent material properties. The computed profiles of strain rate and viscosity were examined in light of the existing literature on thermomechanical processing. The heat and mass flow during welding was found to be strongly three-dimensional. Significant asymmetry of heat and mass flow, which increased with welding speed and rotational speed, was observed. Convective transport of heat was an important mechanism of heat transfer near the tool surface. The numerically simulated temperature fields, cooling rates, and the geometry of the thermomechanically affected zone agreed well with independently determined experimental values.     

Corrosion behavior on the different zones of AA2014 welded aluminum alloy by AA5554 filler aluminum alloy with TIG process: Before and after solution heat treatments followed by ageing

In this work, we have studied the effects of solution heat treatment followed by ageing on the corrosion behavior of AA2014 aluminum alloy welded by AA5554 aluminum alloy. Two samples are then analyzed, in the first case the solution heat treatment is followed by quenching and natural ageing of 90 days (sample 1), and in the second one, the solution heat treatment is followed by quenching and artificial ageing of twelve hours at 190°C (sample 2). The principal observations can be summarized as: evaporation of magnesium in fusion zone, and diffusion of magnesium and copper from the heat affected zone to the fusion zone were identified. Solution heat treatment, quenching and 90 days of natural ageing leads to a uniform corrosion in the heat affected zone and in the fusion one, when the material is immersed for ten seconds in Keller reagent solution. After immersion in 0.3% NaCl chloride solution, and after solution treatment and quenching, we observed that applied artificial ageing at 190°C causes localized corrosion surrounding precipitates and then develops uniform corrosion in all zones, particularly in the fusion one. Finally, it is noted that the surface of different zones became nobler after applying solution heat treatment followed by natural ageing.     

Heat Flow during the Autogenous GTA Welding of Pipes

A theoretical and experimental study of heat flow during the welding of pipes was carried out. The theoretical part of the study involves the development of two finite difference computer models: one for describing steady state, 3-dimensional heat flow during seam welding, the other for describing unsteady state, 3-dimensional heat flow during girth welding. The experimental part of the study, on the other hand, includes: measurement of the thermal response of the pipe with a high speed data acquisition system, determination of the arc efficiency with a calorimeter, and examination of the fusion boundary of the resultant weld. The experimental results were compared with the calculated ones, and the agreement was excellent in the case of seam welding and reasonably good in the case of girth welding. Both the computer models and experiments confirmed that, under a constant heat input and welding speed, the size of the fusion zone remains unchanged in seam welding but continues to increase in girth welding of pipes of small diameters. It is expected that the unsteady state model developed can be used to provide optimum conditions for girth welding, so that uniform weld beads can be obtained and weld defects such as lack of fusion and sagging can be avoided.     

Simulation of Heat Flow During the Welding of Thin Plates

Based on the finite difference method and the enthalpy model of Shamsundar, a computer model was developed to describe the steady state, two-dimensional heat flow during the welding of thin plates. In order to allow accurate computations of the weld pool configuration, the size of the mushy zone and the temperature distribution near the heat source, a grid mesh of variable spacings was used. The heat of fusion, the size and distribution of the heat source, the temperature dependence of thermal properties, the heat conduction in the welding direction and the surface heat loss during welding were considered. The model was first checked with Rosenthal’s analytical solution of welding heat flow using pure aluminum for examples. Experimental results of 6061 aluminum, including the width of the fusion zone and the thermal cycles at positions in both the fusion and the heat affected zones, were then compared with the calculated results of the heat flow model. The agreement was very good. Finally, in order to demonstrate systematically the quantitative effect of welding parameters such as the heat input, the welding speed and the preheating of the workpiece, a series of computations were made based upon 6061 aluminum.     

硬质合金中氮的测定方法研究

介绍了以惰性气体脉冲加热熔融法提取氮 ,再由热导式探测器测定硬质合金中氮的方法 ,并对以Ni篮助熔剂及准确的实验分析条件 ,进行了研究     

Investigations on metallurgical and mechanical properties of CO2 laser beam welded Alloy 825

In the research work, an attempt is made to join nickel-based alloy 825 by employing CO₂ laser beam welding. Successful full penetration weld joint of a 5?mm thick plate is achieved with a very low heat input of 120?J-mm^?1. Narrow weld bead width of 0.6?mm at the root and 1.6?mm at the cap is observed fusion zone; the interface and base metal microstructures have been examined using both optical and scanning electron microscopic techniques to understand the microstructural changes which have occurred due to laser welding. A range of tests of Vickers micro hardness, tensile and impact tests had been performed on the weldment to ascertain the mechanical properties of the joint. Tensile failure at the base metal and a 180° root bend test conducted on the weldment ascertain the soundness of the weld joint produced. An attempt is made to correlate the microstructure and mechanical properties of the weldment. Intermetallics TiN and Al₄C₃ observed in the SEM\EDS analysis at the fusion zone are found to have improved the weld metal strength and hardness.     

Influence of heat treatment on the mechanical properties of an Fe E 460 TMCP steel

Welding is always accompanied by a heat treatment of the base metal. The heat affected zone (HAZ) of multilayer welded joints often shows different microstructures along the fusion line due to varying heat treatments. In order to investigate the mechanical properties of single microstructures weld simulation treatment was applied. The influence of weld simulation parameters such as heating rate and peak temperature was checked in a preliminary step. Several weld simulation treatments finally were used to explain the behaviour of real welded joints. A comparison of fracture mechanics test results from weld simulated microstructures and from real HAZ's shows good agreement for equal heat treatment conditions.     

CA-MIG热源处理下钛/铝异质合金界面显微组织特性

采用Al-Si5焊丝进行TC4钛/1060铝异质结构的CA-MIG连接,采用SEM、EDS等显微分析手段对不同热输入下所获接头的Ti/Al界面显微组织特点、界面附近元素分布进行分析,研究Ti/Al界面特性随热源热输入变化的演变规律。结果表明,CA-MIG热源热输入对Ti/Al界面显微组织具有显著影响。当热源热输入低于0.91 kJ/cm时,钛与铝基焊缝之间仅形成了一层界面反应层。当热源热输入处于0.91~1.55 kJ/cm时,钛与焊缝之间形成了两种Ti/Al界面,一种为单层结构的齿状Ti(Al,Si)₃;另一种由α-Ti(Al,Si)均匀层、Ti₅Si₃纳米颗粒+Ti(Al,Si)₃混合层、齿状Ti(Al,Si)₃层3层结构组成。当热源热输入超过1.55 kJ/cm后,除了上述两种Ti/Al界面外,局部微区钛合金发生熔化,与铝基焊缝之间形成了成分复杂的熔合区,熔合区内存在大量的裂纹缺陷。     

A thermodynamic investigation of crystalline and amorphous Se−Te alloys

The heats of formation, referred to the component elements in their stable crystalline forms, of crystalline Se?Te alloys containing 0 to 100 at. pct Te and amorphous alloys containing 0 to 30 at. pct Te were measured by liquid metal solution calorimetry. The heats of formation of the crystalline and amorphous alloys changed nonmonotonically with composition in a parallel manner. The crystalline alloys had negative heats of formation in the range of 0 to approximately 17 at. pct Te; the largest negative value of approximately?0.235 kcal/g-atom occurred at 10 at. pct Te. At 20 at. pct Te the heat of formation was positive and had a value of approximately 0.115 kcal/g-atom and at higher tellurium concentrations it again turned negative but was very small. The heats of formation of all amorphous alloys investigated were positive. A minimum of approximately 0.810 kcal/g-atom at 10 at.pct Te and a maximum of 1.040 kcal/g-atom at 20 at. pct Te corresponded to the largest negative value and the largest positive value of the heat of formation of the crystalline alloys of the respective compositions. The temperatures of maximum rates of crystallization and fusion and the heat effects associated with the crystallization and fusion of the amorphous alloys were measured by differential scanning calorimetry. With increasing tellurium concentration the temperature of crystallization decreased and the heat effect and the temperature associated with fusion increased.     

Technique and patient care using interbody fusion technology

A new development in spinal surgery uses cylindrical fusion devices for fixation and fusion. Two products, which involve differing procedures, instrumentation, and implants, have been used for more than two years and are becoming more popular as excellent fusion and recovery rates have been reported. This article discusses the historical background of surgery for spinal fusion and describes the preoperative preparation and procedures for both of the products. The conclusion summarizes postoperative care, patient teaching, and preventing possible complications.