Microstructural features and heat flow analysis of atomized and spray-formed Al-Fe-V-Si alloy

Microstructural features of rapidly solidified powders and preforms of Al₈₀Fe₁₀V₄Si₆ alloy produced by spray forming process have been studied. The atomization and spray deposition were carried out using a confined gas atomization process and the microstructural features were characterized using scanning electron microscopy and transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. The microstructure of a wide size range of atomized powders invariably revealed cellular and dendritic morphology. The extent of dendritic region and the dendritic arm spacing were observed to increase with powder particle size. The TEM investigations indicated the presence of ultrafine second-phase particles in the intercellular or interdendritic regions. In contrast, the spray deposits of the alloy showed considerable variation in microstructure and size and dispersion of the second-phase particles at specific distances from the deposit-substrate interface and the exterior regions of the deposit. Nevertheless, considerable homogeneity was observed in the microstructure toward the center of the spray deposit. The formation and distribution of a cubic phase α-Al(Fe,V)Si has been characterized in both atomized powders and spray deposits. A one-dimensional heat flow model has been used to analyze the evolution of microstructure during atomization and also during spray deposition processing of this alloy. The results indicate that thermal history of droplets in the spray on deposition surface and their solidification behavior considerably influence the micro-structural features of the spray deposits.     

A three-dimensional model of the spray forming method

A three-dimensional model has been formulated to calculate the shape of the general preform, using vector calculus. The shape of a rod, tube, plate, or irregular preform can be calculated at given spray forming conditions. The shape of a spray-formed rod was analyzed at various spray forming conditions using the three-dimensional model. The effects of spray forming parameters, such as spray distribution parameters, angular velocity of rotation, withdrawal velocity, spray angle, and eccentric distance on rod shape, were analyzed. The most important parameters affecting the shape of rods are the spray distribution parameters and the withdrawal velocity. The dynamic evolution of rod shape with a stepwise variation of the withdrawal velocity during spray forming was investigated. The effect of a stepwise change of the withdrawal velocity was the same as that of the scanning atomizer. The calculated surface profiles were compared with those of spray-formed 7075 aluminum alloy rods prepared on a pilot scale. The calculated results for the surface profiles were in agreement with those of the spray-formed rods.     

Numerical simulation of temperature distribution and solidification behaviour during spray forming

A mathematical, two-dimensional model for the analysis of the temperature and solidification behaviour in the substrate and deposit for the spray forming process of metals has been developed. Due to the irregular shape of the growing deposit, which changes with spraying time, a grid transformation method was successfully developed for the calculation of the temperature distribution and solidification front in the growing deposit. The influence of process parameters, i.e. thermal conditions of the metal spray at impact, heat transfer coefficient at the surface of the deposit and geometrical parameters, are qualitatively and quantitatively discussed.     

胶莱盆地东北缘与低角度拆离断层有关的金矿成矿作用——以山东海阳郭城金矿为例

山东省海阳市郭城地区位于胶东地块的东部、胶莱盆地的北侧 ,发育着一系列与低角度拆离断层有关的金矿床。按其产出位置 ,可以分为产在拆离断层中的金矿化 (以土堆金矿为代表 )和拆离断层上盘反向断裂裂隙系统中的金矿化 (以沙旺金矿床为代表 )。通过研究这两类代表性金矿床的地质和地球化学特征 ,探讨了胶莱盆地东北缘与低角度拆离断层有关的金矿成矿作用。     

胶莱盆地东北缘与低角度拆离断层有关的金矿陈矿作用——以山东海阳郭城金矿为例

山东省海阳市郭城地区位于胶东地块的东、胶莱盆地的北侧,发育着一系列与低角度拆离断层有关的金矿床。按其产出位,可以分为产在拆离断层中的金矿化(以土堆金矿为代表)和拆离断层上盘反向断裂裂隙系统中的盘矿化(以沙旺金矿床为代表)。通过研究这两类代表性金矿床的地质和地球化学特征,探讨了胶莱盆地东北缘与低角度拆离断层有美的金矿成矿作用。     

Numerical results of temperature distribution and solidification behaviour during spray forming

Based on a grid transformation method, the temperature and solidification behaviour in the substrate and deposit for the spray forming process of metals has been simulated. Numerical results will be compared with experimental data of temperature measurements in the deposit and substrate. Some limitations of this model will be outlined.     

甘南地区加甘滩金矿床主矿体特征及其与区域典型矿床对比分析

甘南地区是甘肃省重要的金矿集中分布区,经过30多年的地质勘查,分别形成了以早子沟、加甘滩、以地南等金矿床为代表的夏河—合作金矿富集区和以大水、辛曲等金矿床为代表的忠曲—大水金矿富集区。采用典型矿床解剖和金矿富集区区域类比的方法,通过系统总结加甘滩特大型金矿床主矿体特征,并对比分析2个金矿富集区勘查程度达到详查或勘探的5个大中型典型金矿床主矿体特征及其控矿因素,以期为甘南地区大中型金矿床地质研究提供范例。加甘滩金矿床主矿体规模以中型为主,金平均品位为2.20×10-6～3.77×10-6,查明金资源量占矿区总资源量的57.27%;对比可知,5个金矿床的矿带规模大,其长度大于1 000 m,控制斜深大于400 m,主矿体数量占矿区全部矿体数量的1.98%～7.14%,除加甘滩金矿之外,其余矿床查明金资源量占矿区总资源量的75%～79%,单个主矿体资源量大于1.5 t,且特大型、大型和中型金矿床分别圈出大型、中型和小型资源量规模的主矿体;夏河—合作矿集区主矿体规模为大中型,金平均品位小于3.5×10-6,忠曲—大水矿集区主矿体规模为中型,金平均品位大于5×10-6,即后者矿体规模相对较小但品...     

4不锈钢-碳钢复合板多道次小变形轧制温度场的数值模拟

基于弹塑性热力耦合有限元法研究了72mm Q235钢基板和14mm 304不锈钢复板11道次变形至12mm复合板的热轧过程,并应用有限元MARC软件二次开发技术建立了温度场模型。模拟结果表明,变形区内,复合板表面温度持续下降,界面温度略有升高;变形区外,表面温度有所回升;随轧制过程进行,轧件高度方向温度梯度逐渐减小;界面处温度呈“S”形,变形区温度变化显著,且随轧制速度提高,升温明显。     

喷射成型锭坯形状的数值模拟研究

建立了描述喷射成型过程中沉积坯外轮廓动态生长的三维数学模型,该模型考虑了喷射成型过程中各种工艺参数的影响,这些工艺参数包括喷嘴的雾化特性值、偏心距离、沉积盘的旋转速度和下拉速度,在计算后进行数据处理得出了锭坯生长的三维外形轮廓,通过与实际喷射成型设备成形的锭坯对比,两种结果符合较好,并可用此模型来预测不同工艺条件下锭坯的外形生长轮廓。     

Modelling of droplet dynamic and thermal histories during spray forming—II. Effect of process parameters

A computer model has been developed to describe the in-flight dynamic and thermal histories of gas atomised droplets as a function of distance during spray forming. The model has been used to investigate the effects of the dynamic and thermal behaviour of individual gas atomised droplets and the cooling and solidification behaviour of the overall spray. The most influential parameters for a given alloy system, in order of importance, are: (i) droplet diameter and, therefore, the droplet size distribution within the spray; (ii) initial axial gas velocity at the point of atomisation and the subsequent gas velocity decay profile; (iii) melt mass flow rate; (iv) melt superheat at the point of atomisation; and (v) alloy composition. Experimental measurements of gas velocities and droplet size distributions during spray forming allow the spray solid fraction at deposition to be calculated and used in a subsequent computer model of billet heat flow to predict the billet top surface temperatures and solid fractions.     

不锈钢-碳钢复合板多道次小变形轧制温度场的数值模拟

基于弹塑性热力耦合有限元法研究了72 mm Q235钢基板和14 mm 304不锈钢复板11道次变形至12 mm复合板的热轧过程,并应用有限元MARC软件二次开发技术建立了温度场模型。模拟结果表明,变形区内,复合板表面温度持续下降,界面温度略有升高;变形区外,表面温度有所回升;随轧制过程进行,轧件高度方向温度梯度逐渐减小;界面处温度呈“S”形,变形区温度变化显著,且随轧制速度提高,升温明显。     

Numerical simulation of tube profile growth during spray forming process

Spray forming is a new type of metal material forming process,which can produce metal blanks such as billet,tube,plate etc.A mathematical model has been developed to forecast the shape evolution of tube billets during the spray forming process.The atomizer mass flux as,radial distribution coefficient bs,draw velocity and diameter of mandrel were considered in this model and the influence of different parameters such as metal flowrate,draw velocity of mandrel,diameter of mandrel on the tube’s shape change were simulated and analyzed in this paper.The simulation results obtained from this model can be provided to engineers as reference.     

非规则管坯喷射沉积成形工艺优化及试验验证

提出了基于往复式喷射成形工艺制备大璧厚非规则管坯的近终形成形工艺及其工艺参数优化方法,以实现坯件从CAD设计到喷射成形的快速制备过程。该工艺方法包括三个阶段:非规则管坯的三维CAD设计、分层处理和单层沉积厚度计算;基于沉积厚度与往复速度和质量流率的对应关系,计算满足各层沉积厚度所对应的控制参数;利用控制系统和执行机构对控制参数进行实时控制和调节,采用往复式多层喷射成形工艺制备满足设计轮廓的管坯。通过试验进行了验证,喷射成形制备的管坯形状和轮廓与CAD设计模型较好地一致,表明了该工艺方法的可行和正确性。     

喷射成形过程中圆锭坯外形生长的数值模拟

通过多次试验后得出雾化喷嘴的雾化特性公式,在此基础上建立了一种模拟喷射成形过程中圆锭坯外形生长的数学模型.该数学模型考虑了喷射成形过程中各种工艺参数,如喷嘴的雾化参数、偏心距离、沉积盘的旋转速度和下拉速度等参数的影响.经过模拟计算,得到了锭坯生长的三维外形尺寸,与实际喷射成形制备的锭坯外形对比,二者吻合很好;采用该模型分析了不同时间下锭坯的轮廓形状、偏心距离以及下拉速度变化后的锭坯轮廓形状.综合分析得出,此数学模型可以预测在不同工艺参数下喷射成形锭坯的外形生长过程.     

Modelling of droplet dynamic and thermal histories during spray forming—I. individual droplet behaviour

A computer model has been developed to describe the in-flight dynamic and thermal histories of gas atomised droplets as a function of distance during spray forming. Modifications of the model have been used to evaluate the relative importance of different physical assumptions in controlling droplet cooling and solidification behaviour, and ultimately the evolution of spray formed billet microstructures. Gas atomised droplet dynamic and thermal behaviour is strongly affected by the distribution of droplet diameters in the two phase spray and the momentum transfer between the droplets and the atomising gas, but is relatively unaffected by the details of the droplet solidification mechanism.     

Engineered Struvite Precipitation: Impacts of Component-Ion Molar Ratios and pH

Struvite precipitation has the potential for removing and recovering phosphorus from agricultural wastewater streams, such as concentrated animal feeding operations wastewater. However, impacts of anticipated component-ion molar ratios and potentially interfering ions are unknown as are the compounding pH relationship with respect to all potential complexes. This research experimentally investigates and mathematically models these factors. Emphasis is placed upon the composition of formed deposits and model validation with experimental data. Results show that calcium is a major interfering ion affecting the deposit composition, decreasing struvite purity. X-ray diffraction (XRD) and scanning electron microscopy + energy dispersive spectrometry were used to study the deposit structure and elemental composition. Results revealed that the precipitates formed at a pH of 8.7 have regular crystal shape, and XRD analysis confirmed that the precipitates are high-purity struvite. Higher pH?(>10) leads to the formation of amorphous precipitate and decreases the struvite purity in the deposits. To maximize struvite purity, the ratio of Ca to P should be less than 0.5 and the pH near 8.7.     

喷射成形硅钢板坯的工艺研究

利用自行研制的大型喷射成形中装置, 对Fe-4.5wt%硅钢板坯的喷射成形工艺进行了研究。还研究了雾化压力和沉积距离对其显微组织的影响。结果表明,在本试验条件下得出的最佳喷射成形工艺,可形成厚度均匀、晶粒细小并致密度良好的板坯,使随后的轧制成为可能。     

Shape, wear & mechanical properties of spray formed hypoeutectic Al-Si alloys

Manufacturing process through spray forming leads to give near-net-shape and fine grain microstructure. In this process Si particles, which are not distributed uniformly in conventional casting process, are distributed uniformly throughout the casting. In the present study disc shape spray form castings were made of Al-6.91Si and Al-10.1Si alloys, and then their shape, wear and mechanical properties were studied. The shape of the deposit was observed to be the most uniform at 30o inclination angle of the substrate. The hardness and tensile strength value of spray formed alloys shows the increment in the mechanical property in contrast to as cast alloys. The wearing properties of Al-10.1Si alloy were found to be better than that of the Al-6.91Si alloy.