Effect of processing parameters on microstructures and mechanical properties of rapidly solidified AlFeVSi hot-extruded product

1　INTRODUCTIONRapidlysolidifiedAlFeVSialloy ,developedus ing planarflowcastingbytheAllied SignalAlu minumCompanyofUSA ,isoneofthemostmatureheat resistantaluminumalloysatpresent.FVS0 6 11,FVS0 812andFVS12 12havebeenappliedinthein dustriesofaviationandaerospacetomeettheneedsofadvancedaircraftsforlightweightstructuralmaterialswithhighspecificstrength ,highspecificstiffnessandexcellentthermalstability[14 ] .Theblanksofrapidlysolidifiedheat resistantalu minumalloywereprocessedbyusingpl…     

Comparative evaluation of X‐ray test results with bend test results for aluminium alloy welded joints

The SiC particle reinforced aluminum alloy has been developed for various machine parts. Aluminum welded machine parts often require welded joints composed of dissimilar alloys. In the present study, electron beam weldability of dissimilar joints was investigated on different combinations of aluminum alloys of 10 mm thickness. The main alloy is 10% SiC particle reinforced Al–Si aluminum alloy. Combination wrought alloys are Al–Si, Al–Mg, Al–Mg–Si and Al–Zn–Mg–Cu alloys. The electron beam machine is a 6 kW high voltage type. The joint groove is of square butt without filler metal.

In the case of SiC reinforced alloy/Al–Si and Al–Mg, joints, weldability was poor because some weld imperfections were recognized such as arcing and other defects. In the case of SiC reinforced alloy/Al–Mg–Si, Al–Zn–Mg–Cu, the cracking sensitivity is low while some small porosity was recognized. Tensile strength became about 150 MPa such as SiC reinforced alloy. Impact values of the SiC reinforced alloy/Al–Mg–Si joint were recovered through 2160 h room temperature ageing. Micro segregation of the Si element was recognized for the SiC reinforced alloy/Al–Mg–Si joint by electron probe microanalyser analysis.     

Al-Zn系高强铸造铝合金强韧化研究现状与展望

轻质高强铸造铝合金在航空航天、汽车轻量化等方面展现出独特的优势。对铸造铝合金成形性能和力学性能进一步优化,对拓宽其应用领域意义重大。本文综述了Al-Zn系高强铸造铝合金的研究现状与进展,重点归纳了高强铸造铝合金(微)合金化、晶粒细化、组织纯净化、热处理优化等方面的强化机制及现有研究成果,并对铸造铝合金目前研发中所存在的问题进行探讨,最后对高强铸造铝合金的发展方向进行了展望,对高强铸造铝合金的发展具有一定的实践和理论指导意义。     

航空铝锂合金热成形研究进展

与传统铝合金相比,铝锂合金拥有更低的密度、更高的比强度、更好的耐腐蚀性,在航空、航天和航海领域得到了广泛应用。铝锂合金的优异性能归因于在铝基体中添加元素锂。但铝锂合金存在常温延伸率低、回弹大和各向异性强等问题,这些问题严重限制了铝锂合金的应用。为解决铝锂合金常温成形性差的问题,国内外学者针对铝锂合金热成形工艺开展了大量研究。本文首先介绍铝锂合金的发展,随后基于基础实验、失稳理论以及损伤理论三个方面介绍铝锂合金热成形研究进展,了解铝锂合金高温宏微观变形机理以及损伤演化规律,从而实现铝锂合金零件在高温条件下成形成性一体化控制;最后对航空铝锂合金热成形的发展趋势进行了展望。本文可为航空铝锂合金材料热成形生产工艺的制定提供一定的理论参考。     

Microstructure and tensile properties of orthorhombic Ti–Al–Nb–Ta alloys

Microstructure and tensile properties of orthorhombic Ti–Al–Nb–Ta alloys have been studied. In order to optimize ductility and strength of the orthorhombic alloys with the nominal compositions of Ti–22Al–23Nb–3Ta and Ti–22Al–20Nb–7Ta, various thermomechanical processing steps were implemented as part of the processing route. With a special heat treatment before rolling to obtain a fine and homogeneous rolled microstructure, the rolled microstructure resulted in a good combination of high tensile yield strength and good ductility of the alloys through available solution and age treatments. The duplex microstructure with equiaxed α₂/O particles and fine O phase laths in a B2 matrix, deforming in α₂+B2+O phase field and treating in O+B2 phase field, possesses the highest tensile properties. The R.T. yield strength and ductility of the Ti–22Al–20Nb–7Ta alloy are 1200 MPa, and 9.8% respectively. The yield strength and ductility values of 970 MPa and 14% were also maintained at elevated temperature (650°C).     

Effect of high-temperature pre-precipitation on mechanical properties and stress corrosion cracking of Al-Zn-Mg alloys

1　INTRODUCTIONMediumandhighstrengthAl Zn Mgseriesaluminumalloysarethe primaryweldingstructurematerialsofaerocrafts ,transportationvehiclesandmilitaryequipments[1,2 ] ,duetoitsbetterweldabilityandexcellenttechnologicalproperty .Buttheexten siveutilizationofthesealloysishamperedbyitspoorstresscorrosioncracking (SCC)resistance[3,4 ] .Ac cordingly ,manystudieshavebeenconcernedwithsuchaproblemashowtoimprovestresscorrosionre sistanceofAl Zn Mgalloyswithnon deterioratedstrength[3,58] .Atpres…     

Recent advances in the deformation processing of titanium alloys

Titanium (Ti) alloys are special-purpose materials used for several critical applications in aerospace as well as non-aerospace industries, and extensive deformation processing is necessary to shape-form these materials, which poses many challenges due to the microstructural complexities. Some of the recent developments in the deformation processing of Ti alloys and usefulness of integrating the material behavior information with simulation schemes while designing and optimizing manufacturing process schedules are discussed in this paper. Discussions are primarily focused on the most important alloy, Ti-6Al-4V and on developing a clear understanding on the influence of key parameters (e.g., oxygen content, starting microstructure, temperature, and strain rate) on the deformation behavior during hot working. These studies are very useful not only for obtaining controlled microstructures but also to design complex multi-step processing sequences to produce defect-free components. Strain-induced porosity (SIP) has been a serious problem during titanium alloy processing, and improved scientific understanding helps in seeking elegant solutions to avoid SIP. A novel high-speed processing technique for microstructural conversion in titanium has been described, which provides several benefits over the conventional slow-speed practices. The hot working behavior of some of the affordable α+β and β titanium alloys being developed recently—namely, Ti-5.5Al-1Fe, Ti-10V-2Fe-3Al, Ti-6.8Mo-4.5Fe-1.5Al, and Ti-10V-4.5Fe-1.5Al—has been analyzed, and the usefulness of the processing maps in optimizing the process parameters and design of hot working schedules in these alloys is demonstrated. Titanium alloys modified with small additions of boron are emerging as potential candidates for replacing structural components requiring high specific strength and stiffness. Efforts to understand the microstructural mechanisms during deformation processing of Ti-B alloys and the issues associated with their processing are discussed.     

Development on research of advanced rare-earth aluminum alloy

1　INTRODUCTIONTheeffectofrareearthandtransitionelementsonthealuminumalloyisevidentfortheirspecialelec tronicstructures ,andthishasattractedattentionsofmanyscientists .Inthepast ,theresearchontherareearthaluminumalloyswascarriedoutmainlyonthebasisofassignmentofthespecifictypeandstrategy ,especiallyinChina ,andexplorationsoftheapplica tionoftherareearths (richresourceinChina)inalu minumalloysweremostlyconcentratedontheeffectofmischmetalonsomecommercialaluminumalloys ,whichwasthecertainoffs…     

Predicting the critical pre-aging time in ECAP processing of age-hardenable aluminum alloys

Age-hardenable Al alloys may be successfully processed by equal channel angular pressing (ECAP) at room temperature, if the processing is carried out immediately after water quenching from the solution treatment temperature. It is important to estimate the critical time for any age-hardenable alloys, since after this time, ECAP processing will cause catastrophic cracking or segmentation at room temperature. In this study, ECAP processing was carried out on two age-hardenable Al alloys (2014 and 7075) at room temperature. The results demonstrated that the critical time could be predicted successfully by using tensile test curves related to different times after quenching. It is also shown that room temperature ECAP processing of these materials for more than a single pass is not possible and causes damage. However, a single pass will have significant effects on the strength of the material.     

Elevated-Temperature Al Alloys for Aircraft Structure

Elevated-temperature powder metallurgy (P/M) aluminum alloys are being developed to replace titanium aircraft structure materials for operation in the 300–600°F temperature range. Typical mechanical properties ofP/M Al?Fe?Ce and Al?Fe?V?Si alloys are superior to those of conventional materials, and cost savings of fifty to seventy percent have been projected for these alloys which can be fabricated and processed using methods similar to those used in the production of conventional aluminum.     

Stress aging of Al–xCu alloys: experiments

Exposure of age-hardenable aluminum alloys to an elastic loading, either for “age-forming” and other manufacturing processes or during utilization at relatively high temperature, may lead to microstructural changes such as a stress-orienting effect of plate-like coherent or semi-coherent precipitates in the alloys. Preferentially oriented θ″/θ′-precipitate structures were quantitatively examined in single-crystal Al–2.5Cu, Al–4Cu and cube-textured Al–5Cu alloys aged to peak strength under compressive stresses. The dependence of the stress orienting of the θ″/θ′-precipitates on the applied stress, aging temperature and the copper content were determined. The effect is discussed and explained within the frame of classical nucleation and growth theories that incorporate the interaction energy between the external stress and the strain fields due to the lattice misfits between the θ″/θ′-precipitates and the Al matrix.     

Vacancy strengthening in Fe3Al iron aluminides

The room temperature strength of FeAl alloys can be increased significantly by freezing in the high thermal vacancy concentrations present at elevated temperatures. In contrast, because of their lower thermal vacancy concentrations, vacancy strengthening in quenched Fe₃Al alloys is believed to be much smaller and has not received much attention to date. In the present work, the influence of annealing time and quench temperature on the room temperature strength of extruded and recrystallized Fe₃Al alloys is evaluated. For aluminum concentrations between 28 and 32 at% and quench temperatures between 400 and 900 °C both the magnitude and the kinetics of strengthening are found to be consistent with reported values for the thermal vacancy concentrations and vacancy migration rates. To assess the potential contributions of other strengthening mechanisms, appropriate heat treatments will need to be designed in follow-on studies that alter microstructural features relevant to those mechanisms while maintaining a constant vacancy concentration.     

On the possibility of scandium alloying of copper-containing aluminum alloys

Scandium alloying of aluminum alloys can substantially improve their operating properties and weld-ability. Commercially scandium-alloyed alloys have been developed for the Al - Mg, Al - Zn - Mg, and Al - Mg - Li systems. The scandium alloying of aluminum alloys containing copper as an alloying component should be performed carefully, because scandium can produce a chemical compound with copper. This worsens the strength properties of preforms and decreases their plasticity and fracture toughness due to the increased volume fraction of the excess phases. In this work, conditions for scandium alloying are determined for the copper-containing alloys D16 and 1933.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, pp. 23 – 27, February, 1995.     

Tensile properties of some copper- and zinc-based alloys: Effects of strain rate and test temperature

This study analyzes the effects of test temperature and strain rate on the tensile properties of some copper-and zinc-based alloys. The copper-based alloys comprised a leaded-tin and an aluminum bronze, whereas the zinc-based alloys were added with various quantities of aluminum. The aluminum bronze attained maximum room-temperature tensile strength, whereas that of the leaded-tin bronze was the least. Among the zinc-based alloys, the one comprising 27.5 mass% aluminum exhibited superior tensile strength, followed by those alloyed with 11.5, 37.5, and 47.5 mass% aluminum in a descending order. Increasing strain rate tended to improve the tensile strength of the alloys. Tensile strength was reduced with an increase in test temperature irrespective of the alloy composition. The aluminum bronze possessed maximum strength regardless of temperature. The leaded-tin bronze attained least strength property at low temperatures, whereas higher test temperatures led to superior strength than the zinc-based alloys. The temperature sensitivity of the strength of the zinc-based alloys decreased with their aluminum content. Tensile elongation of the alloys tended to increase with an increase in strain rate and test temperature. Leaded-tin bronze was least affected in either case. The alloy also attained least elongation irrespective of test conditions. The aluminum bronze showed maximum elongation, at least at high strain rates. In the case of the zinc-based alloys, intermediate range of aluminum concentration led to better elongation. The elongation property of the alloys was affected by temperature in different manners. In a few cases, the elongation initially increased followed by a reduction beyond a specific test temperature, whereas, in other cases, a continuous increase with temperature was noted. The observations made have been discussed in terms of the nature of different microconstituents of the alloys whose effectiveness changes with test conditions. The response of the samples has been further substantiated with their fractographic features and subsurface characteristics.     

Effect of aluminum content on mechanical properties of hydrogenated Mg–Al magnesium alloys

The mechanical properties of hydrogenated Mg–Al magnesium alloys with various aluminum content were investigated. The ductility, yield strength (YS) and ultimate tensile strength (UTS) of the hydrogenated material decreased while the hardness increased with increasing the aluminum content. Microscopic observations of cross-sections of hydrogenated specimens with various Al content revealed that hydrogen cracks extended deeply as the Al content in the Mg–Al alloys increased. Moreover, X-ray diffraction (XRD) analysis revealed that MgH₂ and AlH₃ hydrides are formed during hydrogenation and were found to contribute to hydrogen embrittlement of Mg–Al alloys. However, the embrittled zone was observed to be larger at the fracture surface of Mg–15Al alloy than that of Mg–5Al alloy. Moreover, the fracture surface of Mg–30Al alloy exhibited completely brittle fracture after hydrogenation.     

Moisture and hydrogen-induced embrittlement of iron aluminides

It is now apparent that Fe₃Al and FeAl alloys with less than 40 at.% Al are intrinsically ductile. Brittleness is manifested only in environments providing ready access to hydrogen. Microstructure, alloy content and surface condition may alter somewhat the susceptibility to embrittlement by moisture or by hydrogen, but are key considerations in alloy design for toughness or ductility when aluminum content is within the Fe₃Al-FeAl range. The susceptibility of iron aluminides to moisture and to hydrogen is a major factor hampering their development as structural alloys. Other properties which need to be improved include tensile strength and creep and impact resistance, but approaches to achieve improved strength properties must consider the susceptibility to the external environment. Development of alloys with less than 16% Al appears to be attractive for situations where reduced strength and oxidation resistance can be tolerated because of the insensitivity of these alloys to embrittlement. However, it must be realized that these alloys are not intermetallics.     

Melting,Processing, and Properties of Disordered Fe-Al and Fe-Al-C Based Alloys

This article presents a part of the research work conducted in our laboratory to develop lightweight steels based on Fe-Al alloys containing 7 wt.% and 9 wt.% aluminum for construction of advanced lightweight ground transportation systems, such as automotive vehicles and heavy-haul truck, and for civil engineering construction, such as bridges, tunnels, and buildings. The melting and casting of sound, porosity-free ingots of Fe-Al-based alloys was accomplished by a newly developed cost-effective technique. The technique consists of using a special flux cover and proprietary charging schedule during air induction melting. These alloys were also produced using a vacuum induction melting (VIM) process for comparison purposes. The effect of aluminum (7 wt.% and 9 wt.%) on melting, processing, and properties of disordered solid solution Fe-Al alloys has been studied in detail. Fe-7 wt.% Al alloy could be produced using air induction melting with a flux cover with the properties comparable to the alloy produced through the VIM route. This material could be further processed through hot and cold working to produce sheets and thin foils. The cold-rolled and annealed sheet exhibited excellent room-temperature ductility. The role of carbon in Fe-7 wt.% Al alloys has also been examined. The results indicate that Fe-Al and Fe-Al-C alloys containing about 7 wt.% Al are potential lightweight steels.     

应用人工神经网络模型预测Ti＋10V-2Fe-3A合金的力学性能

采用人工神经网络方法建立了Ti-10V-2Fe-3Al合金机械性能预测的神经网络模型。模型的输入参数包括变形温度、变形程度、固溶温度、时效温度等热加工工艺参数和热处理制度。模型的输出为钛合金最重要的5个机械性能指标，即抗拉强度、屈服强度、延伸率、断面收缩率和断裂韧性。与传统回归拟合公式相比，该模型具有容错性好、通用性强等优点。该模型可以预测Ti-10V-2Fe-3Al合金在不同热加工工艺参数和热处理制度下的机械性能，也可以用于优化热加工参数和热处理制度。     

Performance comparison of AlTiC and AlTiB master alloys in grain refinement of commercial and high purity aluminum

1 Introduction Since AlTiC master alloys were improved greatly as a new type of master alloy used in grain refinement of aluminum and aluminum alloys in the middle of 1980s[1, 2], there were many important progresses in the preparation techniques and the …     

Microstructures of L2_1/L1_2 multi-phase intermetallics in Co-Ni-Al-Ti system

1　ＩＮＴＲＯＤＵＣＴＩＯＮＩｎｔｅｒｍｅｔａｌｌｉｃｃｏｍｐｏｕｎｄｓｈａｖｅｔｈｅ ｐｒｏｍｉｓｅｏｆｈｉｇｈｔｅｍｐｅｒａｔｕｒｅｓｔｒｕｃｔｕｒａｌａｐｐｌｉｃａｔｉｏｎ ,ｗｈｉｌｅｔｈｅｒｏａｄａｈｅａｄｉｓｈｉｎｄｅｒｅｄｂｙｉｔｓｌｏｗｈｉｇｈ ｔｅｍｐｅｒａｔｕｒｅｃｒｅｅｐｒｅｓｉｓｔａｎｃｅａｎｄｐｏｏｒｒｏｏｍ ｔｅｍｐｅｒａｔｕｒｅｄｕｃｔｉｌｉｔｙ .Ｔｈｅ ｐｒｅｖｉｏｕｓｒｅｓｅａｒｃｈｓｕｇｇｅｓｔｅｄｔｈａｔｍｕｌｔｉ ｃｏｍｐｏ ｎｅｎｔａｌｌｏｙｉｎｇｔｏｐｒｏｄｕ…