Quality Indices for Aluminum Alloy Castings: A Critical Review

Several indices are available in the literature to assess the structural quality of cast Al alloys, especially Al-7 pct Si-Mg alloys that are based on tensile test results. Some of these indices, most notably the one developed by Drouzy et al., provide a number that necessarily does not have a physical meaning, whereas the others are a measure of what fraction of the expected tensile performance is achieved. These indices are analyzed in depth, their similarities and shortcomings are discussed in detail, and recommendations are made.     

Oxidation of Aluminum Melts with Rare-Earth Metals

Thermogravimetry studies show that the oxidation of aluminum–rare-earth metal (R) melts obeys a parabolic law. The true oxidation rate of the melts is on the order of 10^–4–10^–3 kg/(m² s). In the Al–R systems, the minimum oxidation rate corresponds to the compositions of intermetallic compounds. The oxidation rate of a melt is shown to increase with temperature. It is found by IRS (infrared spectroscopy) and XRD (X-ray diffraction) that the melt oxidation products consist of γ-Al₂O₃, R₂O₃ (R = La, Ce, Pr, Nd, Y, Sc), CeO₂, and rare-earth metal monoaluminates RAlO₃ (CeAlO₃, LaAlO₃, NdAlO₃).     

铝合金-镁合金间搅拌摩擦异质焊接研究现状

综合了近几年铝-镁搅拌摩擦异质焊的研完成果,分析和讨论以下几个方面的内容:(1)铝.镁异质焊的焊接性能及其影响因素;(2)焊接过程中的热输入情况及焊缝处的温度分布;(3)焊缝的力学性能及其影响因素;(4)焊缝的宏观、微观组织及其在局部升温和塑性变形下的演化过程,着重分析了金属间化合物的生成、形貌和分布、及其对焊缝力学性...     

Preliminary Analysis of Aluminum Matrix Compositions for Composites Reinforcement with Carbon Fibers

In the liquid phase methods of obtaining the composites, one of important conditions is contact between liquid metal and the reinforcement. In the system of aluminum and carbon fiber, proper connection between liquid and the fibers depends not only on the wetting conditions but also on the reactivity of the components. In the processes of infiltration, one of the factors conducive to such a connection is the chemical composition of the alloy matrix. The composition of the alloy also decides on technological properties such as castability and shrinkage. The paper presents the results of modification AlSi9Cu(Fe) and AlSi9Mn base alloy with addition of magnesium and strontium. The scope of researches includes analysis of the structure alloys before and after modification and results of the compared metal flow in the gravity casting to graphite mold. The mold applied in the study allows the analysis of metal flow in ducts of varying cross section. In case of modified alloy AlSi9Cu(Fe) + 1% Mg + 0.03%Sr was observed a slight decrease of fluidity. While in the case of alloy AlSi9Mn +1% Mg +0.03%Sr length of filled increased comparing to similar beams on base alloy. The aim of modifying the chemical composition of the base alloy was to improve wettability in the Al/CF system during the infiltration process. In the case of an alloy AlSi9Cu(Fe), intended for use in the high pressure die casting (HPDC) process, small change of fluidity has no significant meaning. While for AlSi9Mn the effect of improving the melt fluidity is beneficial from the standpoint of technology GPI.     

Microstructural Evolution During Friction Surfacing of Dissimilar Aluminum Alloys

The microstructural evolution during friction surfacing of an aluminum alloy 6082-T6 rod on an aluminum alloy 2024-T351 substrate was characterized using the electron backscatter diffraction technique. Crystallographic data were obtained from several regions in the consumable material and in the deposited material. From the results, it can be deduced that the grain structure formation was a complex process governed by the geometrical effect of strain and the superposition of continuous and discontinuous dynamic recrystallizations.     

铝合金/Q235钎剂涂层钢板异种金属CMT焊接分析

采用CMT(Cold Mental Transfer,冷金属过渡焊)焊接技术,分别对5083铝合金和6061铝合金与Q235钎剂涂层钢板进行焊接实验。采用NOCLOCK+30%Zn粉的钎剂配方和相同的焊接工艺参数,对焊缝界面组织的SEM和EDS观察分析,研究不同母材对铝合金/钢异种金属焊接的影响。结果表明:采用该钎剂配方可以基本满足铝合金/钢异种金属焊接的要求;铝母材中镁含量越高,得到的接头性能越差。     

铝板坯连铸连轧生产新工艺-Hazelett法

介绍了Hazelett（哈兹列特法）铝带坯连铸连轧生产线的工艺特点、应用范围及与其它生产工艺方案的比较优势。     

铝板坯连铸连轧生产新工艺-Hazelett法(续)

2．2哈兹列特工艺的产品质量 由于连铸机具有2000mm长的铸造模区,铸坯在纵向和横向的固化条件均受到严格的控制,固化速度比直冷铸锭工艺要快得多,故可得到非常致密、均匀的晶粒。由于铝合金液体快速冷却凝结,有效地避免了表面成份偏析和中心成份偏析,无热连轧带坯特有的不均匀的方向性及较强的结晶组织^[3],     

Evaluation of the Effects of Rotary Degassing Process Variables on the Quality of A357 Aluminum Alloy Castings

Metallurgical and Materials Transactions B - The effects of rotary degassing process variables on the melt and casting quality have been investigated using reduced pressure test results and quality...     

Prediction of Fatigue Performance in Aluminum Shape Castings Containing Defects

Fatigue properties of cast aluminum components are controlled by maximum defect size in the material. The larger the maximum defect size, the lower the fatigue strength and life. In the presence of casting defects, crack initiation can be ignored and fatigue life is mainly spent in crack propagation. Therefore, fatigue life of aluminum castings can be predicted by long or short crack growth models. The main problem is defining a starting defect size from readily available data, such as twodimensional (2-D) pore size measurements on metallographic sections. In this article, an extremevalue statistics (EVS) method was used to estimate the maximum defect size in 319 castings from conventional metallographic data. The maximum defect size predicted by EVS agrees quite well with the initiation defect sizes measured from fracture surfaces, and the predicted fatigue life is in reasonable agreement with the experimental data.     

Formation of Quasicrystals and Related Structures in Systems of Aluminum with Transition Metals. Part 1. Binary Systems Formed by Aluminum with 3d Metals

Quasiperiodic phases (quasicrystals) with symmetries forbidden by classic crystallography have been observed in systems of aluminum with transition metals. In binary systems, these phases are metastable; they were obtained for the first time by rapid solidification of melts. We consider the formation of the quasicrystals and we refine the phase diagrams for binary systems A – 3d-M (from V to Ni) in which quasicrystals have been observed.     

Dissimilar Friction-Stir Lap Joining of 5083 Aluminum Alloy to CuZn34 Brass

In this research, lap joining of Al-Mg aluminum alloy and CuZn34 brass was produced by friction-stir welding during which the aluminum alloy sheet was placed on the CuZn34. Optical microscopy, scanning electron microscopy (SEM), X-ray diffraction analysis, and energy-dispersive X-ray spectroscopy (EDS) analysis were used to probe the microstructures and chemical compositions. In addition, the mechanical properties of each sample are characterized using both shear and hardness tests. The optimum parameters resulted in no visible welding cracks and defects. A dark area in the Al/CuZn34 interface contained intermetallic compounds Al₂Cu, Al₄Cu₉, and CuZn. In addition, the results show that using high rotational speeds or low traverse speeds causes the growth of the interfacial intermetallic area.     

Experimental Damage Criterion for Static and Fatigue Life Assessment of Commercial Aluminum Alloy Die Castings

Metallurgical and Materials Transactions A - Defects, particularly porosity and oxides, in high-pressure die casting can seriously compromise the in-service behavior and durability of products...     

用电解铝液生产铝加工坯料的熔体净化方法探讨

简要分析了电解铝液的特殊性，以及利用电铝液生产铝加工坯料存在的一些不足之处，特别是产品的夹渣和气孔缺陷不容忽视。介绍了国内外的熔体净化方法。针对目前的生产工艺，提出了增加炉前熔体净化处理的方案。指出通过炉前、炉内、炉外的净化处理，以及对熔炼过程的严格控制．熔体的纯净度完全可以达到铝加工坯料的要求。     

Detection of a Pool in Semi-Continuous Castings Made of Heat-Treatable Aluminum Alloys

Various products (sheets, sections, etc.) manufactured by metal forming (rolled products, forged pieces, etc.) from semi-continuous castings are widely used in the aerospace industry. The so-called pool, which is the conical volume of a liquid metal, exists at the top of the liquid metal. Experience demonstrates that the geometry, the depth, and the shape of the pool substantially affect the structure formation in a casting and its quality. The application of a titanium nitride nanopowder, which is introduced in a melt in the volume of a rod, as a modifier allowed us to find the exact geometry of the pool.     

一种在线铝带材表面缺陷提取方法

本文提出一种对铝带材表面缺陷在线自适应提取方法：首先对由线阵传感器采集来的材料表面图像数据进行高斯平滑和针对目标的空域增强;然后采用基于直方图的一维自适应熵的方法对预处理后的图像进行缺陷目标分割;再用形态学中的闭运算去除目标内部的孤立点和噪声,改善区域的联通性,得到最终的缺陷图像。实验结果表明该方法是一种精度高、耗时少、有效的在线缺陷定位方法。     

Formation of Quasicrystals and Related Structures in Systems of Aluminum with Transition Metals. Part 2. Binary Systems Formed by Aluminum with 4d and 5d Metals

Numerous systems for aluminum with transition metals have been found to contain quasiperiodic phases (quasicrystals) having symmetries forbidden by classical crystallography. These phases are metastable in binary systems and have been obtained by rapid cooling from the liquid or gaseous phases. Binary quasicrystals are considered along with revised phase diagrams for the systems Al – 4d-M and Al – 5d-M (M from Mo to Pd and from W to Pt).     

A Novel Method for Investigating Solutions of Aluminum in Molten Cryolite

In chronopotentiometric work on Fe²⁺ in a cryolite melt (Jentoftsen et al. in Metall. Mater. Trans. B, 2012, vol. 43B, pp. 869?C74), after depletion of Fe²⁺ at the surface of the iron cathode was complete, continuing electrolysis produced a solution of Al in cryolite, provided that the time was less than a few hundred milliseconds. Potential?Ctime curves indicate a diffusion-controlled, 2-electron reduction to form monovalent aluminum.