2D70铝合金淬透性研究

采用16,30℃自然水末端淬火试验方法,并通过对材料硬度和电导率指标的测试分析,研究了不同温度对2D70铝合金材料淬透性的影响,描绘出小同温度下该合金的端淬曲线,对比分析了相同条件下2D70和2124合金的端淬曲线.研究结果表明,2D70合金的淬火敏感性很小,16和30℃水温对该合金端淬效果差别不大,该合金自由端淬淬透深度至少大于150 mm.     

铝合金淬火过程中性能预报技术的研究现状

铝合金淬火过程中的性能预报技术在冶金工业中具有重要的作用.在铝合金析出动力学的基础上阐述了淬火因子分析在性能预报中的应用,其最大性能损失不超过10%～15%.通过中断淬火技术可以生成铝合金的TTP曲线,使合金从固溶时效温度缓慢冷却至TTP曲线临界温度区域以上的某一温度,然后迅速冷却至室温,可以减小温度梯度引起的残余应力而不明显影响合金的力学性能.     

2219铝合金的TTT曲线与微观组织

采用分级淬火方法测定2219铝合金的时间-温度-电导率(TTT)曲线。利用EDS和TEM等分析手段并结合Avrami方程,研究2219铝合金在等温过程中的组织变化和相变动力学。结果表明:合金TTT曲线的鼻尖温度为440℃,淬火敏感温度区间为300~480℃;等温保温时,过饱和固溶体分解析出第二相粒子,在440℃附近,第二相(主要为θ平衡相)的析出速率达到最高;鼻尖温度的高相变驱动力和较快的扩散速率是θ相析出和长大的主要原因,建议在淬火敏感区间应加快淬火冷却速率避免粗大平衡相的析出,而高于淬火敏感区间温度时可适当降低冷却速率减小热应力的影响。     

基于微观偏析模型的Mn-Cr系齿轮钢淬透性带宽

 运用凝固传热模型,计算出了连铸坯在不同凝固阶段的冷却速率,对经典的BF微观偏析模型进行了修正,并以此为基础建立了由化学成分的不均匀性导致的Mn-Cr系齿轮钢淬透性带宽预测模型,分析了不同二次冷却强度对淬透性带宽的影响。由淬透性带宽预测模型得知,20CrMnTi连铸坯试样淬透性带宽呈抛物线状分布,淬透性带宽曲线在端淬距离0～15 mm范围内呈上升趋势,距离端淬距离超过15 mm时呈下降趋势,距离端淬约15 mm处试样的淬透性带宽取得最大值;适当提高二冷区冷却强度可以缩小连铸坯试样的最大淬透性带宽。     

单面淬冷装置在28Mn2钢淬火处理中的应用

根据30Mn钢的CCT曲线和淬透性。通过比较法,可以近似得出28Mn2钢CCT曲线和淬透性,即当冷却速度大于60℃/s时,能得到50%以上的马氏体组织,淬透性能满足单面冷却φ114.3×6.35以下规格油井管淬火硬度要求。在此基础上设计了在辊底式热处理炉上对钢管进行单面冷却淬火装置。结果表明,经此种装置淬火冷却后,钢管的硬度指标均达到了API 5CT标准要求。该淬冷装置可用于对N80-Q钢级的油井管淬火冷却处理。     

成分对Al-Zn-Mg-Cu超强铝合金淬火敏感性及组织性能的影响

7056超强铝合金具有较高的强韧性及耐蚀性,是近几年研究的热点铝合金之一,但国际上对该合金淬火敏感性的研究仍未见报道。采用末端淬火实验,结合扫描电子显微镜(SEM)和透射电子显微镜(TEM)观察及Thermo-calc模拟软件对Al-Zn-Mg-Cu超强铝合金进行相图计算,对比研究了7150, 7055, 7050和7056 4种Al-Zn-Mg-Cu超强铝合金的淬火敏感性及组织性能。研究表明, 7055, 7150, 7050, 7056 4种合金淬透层深度分别为40, 60, 90, 80 mm; T6状态下, 7056合金端部和内部硬度高于7055合金,显著高于7150和7050合金。进一步研究Cu含量对7056合金的淬火敏感性及组织性能的影响,表明7056合金随着Cu含量的降低,淬火敏感性显著降低, Cu含量达到7056合金成分下限时,合金单边淬透深度达100 mm;拉伸强度与塑性变化不大,抗拉强度处在675～685 MPa之间,屈服强度处在625～635 MPa之间,延伸率在10%～11%区间内波动,无明显规律;电导率提高, 1.03%Cu时合金电导率达35%IACS。7056合金兼具超强和高淬透性的特性与其低Cu高Zn合金成分有关。     

提高强化时效铝合金变形能力的方法

<正>美国专利US5948185本发明推荐一种采取折边方法实现提高结构件连接的强化时效铝合金塑性的方法。该方法包括在10s内将合金折边区加热到250~500℃、对该区进行淬火、淬火之后3h以内进行折边。淬火软化区强度的复原通过冷变形(折边)及后续时效进行。本发明方法用于2×××(Al-Cu-Mg)、6×××(Al-Si-Mg-Cu)和7×××(Al-Zn-Mg-Cu)系合金。     

浅谈7系铝合金管材的小弯曲半径加工技术

7XXX系铝合金中所包含的Al-Zn-Mg-Cu系铝合金属于超硬铝,具有焊接性能和加工性能优良、热处理效果佳、密度低等一系列优点。正是因为如此,早在20世纪40年代末期,7XXX系铝合金就已经被应用于航空航天等高端制造业。时至今日,更是被广泛应用于多个产业领域,在我国社会主义市场经济发展体系中的石油化工、电力系统、管道工程和航天航空等经济产业的发展繁荣过程中占据着十分重要的地位,起到不可或缺的关键作用。本篇论文正是结合相关的理论知识和实践经验来研究分析7XXX系铝合金管材的弯曲加工技术的应用状况,并且从中总结与归纳出高效应用7XXX系铝合金管材的弯曲加工技术对我国未来制造业乃至整个社会主义市场经济的可持续长远良好发展所产生的积极影响和功能作用。     

7A04棒材在线挤压工艺开发

7A04铝合金属于Al-Mg-Zn-Cu系超高强度铝合金,由于7系合金的特性,很少采用在线淬火生产。通常挤压生产时都采用离线淬火处理,然后再时效处理。本次新工艺开发通过对前期工艺开发方案的合理设计,提高了铸锭的温度以及挤压速度,并且考虑选用了不同的时效制度,间接性地提高了淬火的温度,控制棒材淬火前温度≥400℃,从而有效地实现了7A04在线挤压生产的可能。结果表明,在淬火温度达到一定固溶温度时,并充分有效固溶,之后通过后期的时效强化,可以得到相应的不同性能的产品,从而有效提高生产率并减少能耗。     

微量Ag对7XXX系超高强铝合金性能的影响

通过拉伸实验及时效曲线研究了回归时间对试验用Al—Zn—Mg—Cu系铝合金力学性能的影响，结果表明不含Ag的7XXX合金随回归时间的增加强度下降，延伸率在300s时达到峰值；而由于微量Ag的加入，改变了GP区及η′相溶解温度范围，提高了7XXX铝合金GP区及η′相的稳定性，合金经回归再时效处理后强度略有下降，延伸率有较大幅度的增加。     

Influence of main components and transition metals on the structure and properties of melt-quenched high-strength aluminum alloys of the Al-Zn-Mg-Cu system

The application of melt quenching for the production of high-strength heat-treatable Al-Zn-Mg-Cu aluminum alloys is considered. The complex multifactor mechanism of hardening of these materials is explained on the basis of their structure and mechanical properties, and a quantitative estimation of individual hardening factors is presented. The influence of the main alloy components on the phase composition, structure and properties of the alloys has been analyzed, and the ultimate total contents of the components and their weight ratio that ensure the optimal set of properties are determined. In addition, the advantage of complex allying of these alloys with various groups of transition metals is established. The possibility of implementation of these approaches is illustrated by the example of production of high-strength melt-quenched Al-Zn-Mg-Cu alloys.     

半连续铸造7136超高强铝合金的组织特征及均匀化处理工艺

以半连续铸造7136铝合金为研究对象, 以铸态组织分析为基础, 采用双级均匀化. 结果表明: 与其他7×××系铝合金相比, 7136铝合金铸态组织没有明显的层片状α(Al)+T共晶相的特征, 也没有发现S相的存在. 基体中的弥散相为微米级的圆形或棒状MgZn₂相, Mg元素和Zn元素随着液态合金的凝固, 在Al基体中以MgZn₂相的形式析出, 为了平衡Mg元素和Zn元素的分配系数, Mg元素和Zn元素从液态向固态迁移, 这也是使得晶内Zn元素和Mg元素偏高的原因. 经过462℃, 24 h单级均匀化, 残留相大致消除. 随着均匀化时间的延长, 残留相有减少的趋势, 但作用相对较小. 经过450℃, 24 h+470℃, 24 h双级均匀化, 差示扫描量热法获取的峰值非常小, 晶间除了少量高熔点Al₇Cu₂Fe相残留, Al₂Cu等其他相已基本消除, 均匀化效果显著.      

Relationship between fracture toughness, fracture path, and microstructure of 7050 aluminum alloy: Part I. Quantitative characterization

The fracture toughness of Al-Zn-Mg-Cu-based 7XXX aluminum alloys decreases with an increase in the extent of recrystallization. In this contribution, the fracture path of plane-strain fracture-toughness specimens of 7050 alloy (a typical alloy of the 7XXX series) is quantitatively characterized as a function of degree of recrystallization, specimen orientation, and aging condition. The fracture path is quantitatively correlated to fracture toughness, and the bulk microstructural attributes estimated via stereological analysis. In the companion article, these quantitative data are used to develop and verify a multiple-fracture micromechanism-based model that relates the fracture toughness to a number of microstructural parameters of the partially recrystallized alloy plate.     

淬火工艺对含B低合金超厚钢板淬透性能的影响

通过Jominy试验模拟含B低合金超厚钢板的淬火过程,测得不同淬火工艺下实验钢的硬度分布曲线,并借助光学显微镜、俄歇电子能谱等技术手段对低冷速条件下实验钢的显微组织及B晶界偏聚进行了观察和分析.发现在温度不高于920℃条件下,提高淬火温度或适当延长保温时间可显著改善超厚板的淬透性,且在此条件下合适的两次循环淬火可以获得更为理想的淬透性.温度高于920℃后,单次淬火或两次循环淬火均不利于实验钢的淬透性能的改善.      

挤压铝型材在线精密淬火技术和装置

本文较全面地论述了铝合金挤压材在线淬火的基本原理与工艺参数的选定重点介绍了不同铝合金挤压型材的现代精密水雾气淬火装置的结构、工作原理与控制系统,对提高6XXX和部分7XXX铝合金型材的生产效率和产品质量有较好的效果。     

复合添加Zr、Cr、Pr对超高强铝合金腐蚀和断裂行为的影响

采用铸锭冶金法制备Al-Zn-Mg-Cu-Zr合金和Al-Zn-Mg-Cu-Zr-Cr-Pr合金。通过金相和扫描电子显微分析以及拉伸性能、极化曲线、晶间腐蚀、剥落腐蚀与应力腐蚀等性能测试,研究复合添加Zr、Cr和Pr对Al-Zn-Mg-Cu合金腐蚀和断裂行为的影响。结果表明,复合添加Zr、Cr和Pr可显著抑制Al-Zn-Mg-Cu合金的再结晶和晶粒长大,从而提高该合金的抗腐蚀能力和力学性能。与单独添加Zr的Al-Zn-Mg-Cu合金相比,复合添加Zr、Cr、Pr的相同合金的断裂韧性KIC从20.22 MPa.m1/2提高到26.83 MPa.m1/2,应力腐蚀开裂界限应力强度因子KISCC由9.8 MPa.m1/2提高到17.6 MPa.m1/2,抗拉强度、屈服强度及伸长率均有所提高。研究还发现,再结晶晶粒的晶界为腐蚀和断裂的优先选择路径,抑制再结晶和晶粒长大至关重要。     

回收工艺对再生铝合金性能影响述评

铝合金因其密度小、强度高、耐腐蚀、加工性能好的优点,已经成为工业应用第二大金属材料。随着原铝产量下降和现役铝合金材料使用年限逐渐到期,具有节约矿产与能源、经济社会效益高、可持续发展等特点的再生铝产业逐渐受到关注。然而,经过回收再生的铝材由于成分混杂等原因,性能往往有所下降。因此提升再生铝合金性能的方法成为相关领域研究的重点。文中介绍了近年来国内外有关提升再生铝合金性能方法的研究进展,对废铝预处理、合金成分调配、熔体精炼、热加工工艺的发展进行了总结,概述了提升固态回收再生铝合金性能的最新研究进展,并对再生铝技术的发展提出展望。      

Aging kinetics of aluminum alloy 7050

Precipitation hardening at room temperature (natural aging) and isothermal precipitation hardening at 422 to 455 K beyond the point of peak strength (overaging) were studied. Natural aging kinetics of the increase in strength and resistivity were comparable with those of alloy 7075. Alloy 7050, however, develops peak strength by aging at higher temperatures. This ability of 7050 to develop peak strength upon aging in the temperature region used to improve the resistance to stress-corrosion cracking and toughness of 7XXX alloys is attributed to the effect of Cu on increasing the temperature range of G.P zone stability.     

A Methodology to Predict the Effects of Quench Rates on Mechanical Properties of Cast Aluminum Alloys

The mechanical properties of age-hardenable Al-Si-Mg alloys depend on the rate at which the alloys are cooled after the solutionizing heat treatment. Quench factor analysis, developed by Evancho and Staley, was able to quantify the effects of quenching rates on the as-aged properties of an aluminum alloy. This method has been previously used to successfully predict yield strength and hardness of wrought aluminum alloys. However, the quench factor data for aluminum castings is still rare in the literature. In this study, the time-temperature during cooling and hardness were used as the inputs for quench factor modeling. The experimental data were collected using the Jominy end quench method. Multiple linear regression analysis was performed on the experimental data to estimate the kinetic parameters during quenching. Time-temperature-property curves of cast aluminum alloy A356 were generated using the estimated kinetic parameters. Experimental verification was performed on a cast engine head. The predicted hardness agreed well with that experimentally measured. The methodology described in this article requires little experimental effort and can also be used to experimentally estimate the kinetic parameters during quenching for other aluminum alloys. This article is based on a presentation made in the symposium “Simulation of Aluminum Shape Casting Processing: From Design to Mechanical Properties” which occurred March 12–16, 2006, during the TMS Spring meeting in San Antonio, Texas, under the auspices of the Computational Materials Science and Engineering Committee, the Process Modeling, Analysis and Control Committee, the Solidification Committee, the Mechanical Behavior of Materials Committee, and the Light Metal Division/Aluminum Committee.     

Influence of corrosion deposits on near-threshold fatigue crack growth behavior in 2xxx and 7xxx series aluminum alloys

The role of corrosion deposits in influencing the near-threshold fatigue crack propagation behavior of 2XXX and 7XXX series aluminum alloys is examined in detail. The composition, thickness, and distribution of fracture surface oxide films are characterized with the aid of X-ray photoelectron spectroscopy, scanning Auger spectroscopy, and secondary ion mass spectroscopy analyses. It is found that the extent of crack closure due to corrosion debris in aluminum alloys is strongly dependent on the composition and aging treatment. The results suggest that environmentally-influenced near-threshold crack propagation in some aluminum alloys is controlled by twoconcurrent andmutually-compctitive mechanistic processes: a dominant role of crack closure due to corrosion deposits (which tends toarrest completely the near-threshold crack) and a strong embrittling effect (which considerablyincreases near-threshold crack growth rates) concomitantly with the crack tip oxidation phenomenon in the moist medium. The near-threshold corrosion fatigue characteristics of aluminum alloys are contrasted with those in a wide range of steels in order to gain an insight into the various