Synergistic effect of gradient Zn content and multiscale particles on the mechanical properties of Al-Zn-Mg-Cu alloys with coupling distribution of coarse-fine grains

This study investigated the influence of graded Zn content on the evolution of precipitated and iron-rich phases and grain struc-ture of the alloys,designed and developed the Al–8.0Zn–1.5Mg–1.5Cu–0.2Fe(wt%)alloy with high strength and formability.With the increase of Zn content,forming the coupling distribution of multiscale precipitates and iron-rich phases with a reasonable matching ratio and dispersion distribution characteristics is easy.This phenomenon induces the formation of cell-like structures with alternate distribu-tion of coarse and fine grains,and the average plasticity–strain ratio(characterizing the formability)of the pre-aged alloy with a high strength is up to 0.708.Results reveal the evolution and influence mechanisms of multiscale second-phase particles and the corresponding high formability mechanism of the alloys.The developed coupling control process exhibits considerable potential,revealing remarkable improvements in the room temperature formability of high-strength Al–Zn–Mg–Cu alloys.

高强Al-Zn-Mg-Cu合金静态再结晶模型及组织演变

采用Gleeble 3800热模拟试验机对航空用Al-Zn-Mg-Cu合金的热变形行为进行了测试,对变形后的微观组织进行了表征,系统分析了静态软化行为,建立了静态再结晶动力学模型。结果表明:实验用航空Al-Zn-Mg-Cu合金的静态再结晶激活能为129162 J·mol^(-1),静态再结晶体积分数受变形温度、变形程度、变形速率的影响,且变形温度对静态再结晶影响最明显;变形速率一定时,变形温度越高,道次停留时间的影响越不明显;350℃低温变形后,α-Al基体晶粒内部仍存在大量的位错缠结;400℃中温变形后,位错运动能够充分进行,部分晶粒发生了再结晶;450℃高温变形后,基体晶粒基本全部完成了再结晶,基体晶粒内部发现5~25 nm尺寸范围的Al-Zn-Mg-Cu四元相粒子;对于不同热变形条件,模型预测值的误差在0.008~0.0625范围内,动力学模型的计算结果精确度较高。

基于机器学习的Al-Zn-Mg-Cu合金快速设计

提出一种基于机器学习的合金快速设计系统(ARDS),以定制所需性能的合金制备策略或预测制备策略所对应的合金性能。为此,分别对3种回归算法:线性回归(LR)、支持向量回归(SVR)和人工神经网络(BPNN)进行建模和比较以训练多性能预测模型。其中,应用SVR构建的机器学习模型被证明是最佳的。然后,基于生成对抗网络(GAN)模型原理,构建Al-Zn-Mg-Cu系铝合金快速设计系统(ARDS)。对ARDS的预测可靠性进行验证。结果表明,为了能够获得准确的制备策略,系统中极限抗拉强度(UTS)、屈服强度(YS)和伸长率(EL)的输入上限分别约为790 MPa、730 MPa和28%。此外,基于ARDS预测结果,制备了一种性能优异的新型铝合金材料,其UTS为764 MPa、YS为732 MPa、EL为10.1%,进一步验证了ARDS的可靠性。

锌镁比对Al-Zn-Mg-Cu-Er-Sc-Zr合金显微组织与耐腐蚀性能影响的研究

通过调整Al-Zn-Mg-Cu-Er-Sc-Zr合金中的Mg元素含量,研究了Zn/Mg比的变化对合金相演变以及腐蚀性能的影响规律。结果表明:Al_(8)Cu_(4)Er相、Al_(3)(Er,Sc)相与含Fe相存在明显的伴生关系,二者依附于含Fe相生长。Zn/Mg比的变化可显著改变三者间的交互形式,高的Zn/Mg比例有利于稀土相独立生长,且在比值为4.18的条件下,Al_(8)Cu_(4)Er相与含Fe相均得到了显著细化。细化的晶界第二相使腐蚀坑深度仅为82μm,而连续的伴生混合相、粗大稀土相等均会不同程度降低合金的耐蚀性能。

淬火冷却方式及宏观取向对Al-Zn-Mg-Cu合金力学性能的影响

以7050铝合金为研究对象,研究热处理状态(空冷时效与水冷时效)和宏观取向(与轧制方向成0°,45°,90°)耦合作用对合金力学性能的影响。结果表明:水冷时效态的样品中析出相细小均匀弥散,晶界无析出带较窄。在空冷时效态下,过饱和的溶质不仅会以半共格的Al3Zr为核心形成粗大析出相,还会沿位错大量析出。此外,与水冷时效态相比,空冷时效态晶界相尺寸大幅增加,晶界无析出带显著宽化,不同宏观取向样品的强度和伸长率都明显下降。宏观取向对两种状态样品强度的差值影响较小,但对伸长率的差值影响较大。当拉伸方向与轧制方向成45°方向时,空冷诱导的伸长率下降幅度最小;当拉伸方向与轧制方向成90°时,下降幅度最大。

高Zn含量Al-Zn-Mg-Cu系合金的热处理技术研究综述

综述了高Zn含量(质量分数不小于7%)Al-Zn-Mg-Cu系合金的研究现状,重点介绍了高Zn含量Al-Zn-Mg-Cu系合金热处理技术(均匀化处理、固溶处理、时效处理及形变热处理)的研究近况,阐述了不同热处理技术对高Zn含量Al-Zn-Mg-Cu系合金组织性能的影响机制,展望了高Zn含量Al-Zn-Mg-Cu系合金发展趋势及前景,旨在为Al-Zn-Mg-Cu合金综合性能的提升及铝合金材料产业的持续发展提供参考。

均匀化对Al-Zn-Mg-Cu合金第二相与晶粒尺寸的影响

采用光学显微镜(OM)、扫描电镜(SEM)、差示扫描量热仪(DSC)表征,研究了均匀化过程中Al-Zn-Mg-Cu合金的微观组织演变。结果表明,铸态合金晶界中存在大量难溶相Al7Cu2Fe及非平衡共晶相Mg(Zn,Cu,Al)2、Al2CuMg相,在经过420℃/8 h的单级均匀化处理后,部分难溶相和非平衡共晶相回溶到基体中,但还存在大量枝晶偏析,继续进行470℃/36 h第二级均匀化后,非平衡共晶组织和枝晶偏析完全消除。合金的平均晶粒尺寸在两个阶段的均匀化中呈现随时间延长而增加的趋势,基体中残留相及共晶组织的面积分数随保温时长增加而减小,第二级均匀化达到36 h时,相面积分数仅为0.34%,表明均匀化已经非常充分。经过均匀化动力学分析,得出在第二级均匀化温度为470℃时,第二相充分回溶所需保温时间约为37 h,与均匀化的实验结果吻合。

Strengthening mechanism of T8-aged Al-Cu-Li alloy with increased pre-deformation

The microstructure evolution and mechanical properties of a T8-aged Al-Cu-Li alloy with increased pre-deformation(0-15%) were investigated,revealing the microstructure-strength relationship and the intrinsic strengthening mechanism.The results show that increasing the pre-deformation levels remarkably improves the strength of the alloy but deteriorates its ductility.Dislocations introduced by pre-deformation effectively suppress the formation of Guinier-Preston(GP) zones and provide more nucleation sites for T1 precipitates.This leads to more intensive and finer T1 precipitates in the samples with higher pre-deformation levels.Simultaneously,the enhanced precipitation of T1 precipitates and inhibited formation of GP zones cause the decreases in number and sizes of θ′ precipitates.The quantitative descriptions of the strength contributions from different strengthening mechanisms reveal that strengthening contributions from T1 and θ′ precipitates decrease with increasing pre-deformation.The reduced diameters of T1 precipitates are primarily responsible for their weakened strengthening effects.Therefore,the improved strength of the T8-aged Al-Cu-Li alloy is mainly attributed to the stronger strain hardening from the increased pre-deformation levels.

Damage characteristics of Cu−Cr−Zr alloy rail of electromagnetic railgun after simulated launch

The damage characteristics of different speed sections of Cu−Cr−Zr alloy rail after simulated launch were studied.The microstructure,morphologies and properties of samples were investigated by using XRD,XPS,EBSD,SEM,hardness test,electrochemical test and DSC techniques.It was found that deposition layers were formed on the surfaces of the simulated launch samples.The thickness and surface roughness of these deposition layers increased with increasing the heat effect,suggesting a launch speed dependent damage degree of the arc ablation.The hardness variation of samples is attributed to the effects of the deposition layer and deformation hardening.The surface deposition layer affects corrosion resistance and crystalline characteristics,leading to changes in subsequent service performances.Additionally,the surface texture and plastic deformation ability of the samples are related to the recrystallization degree and deformation grain amount.

Corrosion behavior of 2A97 Al-Cu-Li alloys in different thermomechanical conditions by quasi-in-situ analysis

As a promising material in the aircraft industry,2A97 Al-Cu-Li alloy exhibits high corrosion susceptibility that may limit its application.In the present work,to illustrate the influences of precipitate and grain-stored energy on localized corrosion evolution in 2A97 Al-Cu-Li alloy,cold working and artificial aging were carried out to produce 2A97 Al-Cu-Li alloys under different thermomechanical conditions.Quasi-in-situ analysis,traditional immersion test and electrochemical measurement were then conducted to examine the corrosion behavior of 2A97 alloys.It is revealed that precipitate significantly affects Cu enrichment at corrosion fronts,which determines corrosion susceptibility of alloys,whereas grain-stored energy distribution is closely associated with localized corrosion propagation.It is also indicated that quasi-in-situ analysis exhibits a consistent corrosion evolution with traditional immersion tests,which is regarded as a proper method to explore localized corrosion mechanisms by providing local microstructural information with enhanced time and spatial resolutions.

Effect of cold rolling deformation on microstructure evolution and mechanical properties of spray formed Al−Zn−Mg−Cu−Cr alloys

The impact of cold rolling deformation,which was introduced after solid solution and before aging treatment,on microstructure evolution and mechanical properties of the as-extruded spray formed Al−9.8Zn−2.3Mg−1.73Cu−0.13Cr(wt.%)alloy,was investigated.SEM,TEM,and EBSD were used to analyze the microstructures,and tensile tests were conducted to assess mechanical properties.The results indicate that the D1-T6 sample,subjected to 25%cold rolling deformation,exhibits finer grains(3.35μm)compared to the D0-T6 sample(grain size of 4.23μm)without cold rolling.Cold rolling refines the grains that grow in solution treatment.Due to the combined effects of finer and more dispersed precipitates,higher dislocation density and smaller grains,the yield strength and ultimate tensile strength of the D1-T6 sample can reach 663 and 737 MPa,respectively.In comparison to the as-extruded and D0-T6 samples,the yield strength of the D1-T6 sample increases by 415 and 92 MPa,respectively.

Improving comprehensive properties of Cu-11.9Al-2.5Mn shape memory alloy by adding multi-layer graphene carried by Cu_(51)Zr_(14)inoculant particles

In order to improve the comprehensive properties of the Cu-11.9Al-2.5Mn shape memory alloy(SMA),multilayer graphene(MLG)carried by Cu_(51)Zr_(14)inoculant particles was incorporated and dispersed into this alloy through preparing the preform of the cold-pressed MLG-Cu_(51)Zr_(14)composite powders.In the resultant novel MLG/Cu-Al-Mn composites,MLG in fragmented or flocculent form has a good bonding with the Cu-Al-Mn matrix.MLG can prevent the coarsening of grains of the Cu-Al-Mn SMA and cause thermal mismatch dislocations near the MLG/Cu-Al-Mn interfaces.The damping and mechanical properties of the MLG/Cu-Al-Mn composites are significantly improved.When the content of MLG reaches 0.2 wt.%,the highest room temperature damping of 0.0558,tensile strength of 801.5 MPa,elongation of 10.8%,and hardness of HV 308 can be obtained.On the basis of in-depth observation of microstructures,combined with the theory of internal friction and strengthening and toughening theories of metals,the relevant mechanisms are discussed.

Influence of thermomechanical treatment on recrystallization and softening resistance of Cu-6.5Fe-0.3Mg alloy

The recrystallization and softening resistance of a Cu-6.5Fe-0.3Mg(mass fraction,%)alloy prepared by Process 1(cold rolling heat treatment)and Process 2(hot/cold rolling heat treatment)were studied using Vickers hardness tests,tensile tests,scanning electron microscopy and transmission electron microscopy.The softening temperature,hardness and tensile strength of the alloy prepared by Process 2 were 110°C,HV 15 and 114 MPa higher,respectively,than those of the alloy prepared by Process 1 after aging at 300°C.The recrystallization activation energy of the alloys prepared by Process 1 and Process 2 were 72.83 and 98.11 kJ/mol,respectively.The pinning effects of the precipitates of the two alloys on grain boundaries and dislocations were basically the same.The softening mechanism was mainly attributed to the loss of dislocation strengthening.The higher Fe fiber density inhibited the average free migration path of dislocations and grain boundary migration in the alloy,which was the main reason for higher softening temperature of the alloy prepared by Process 2.

HPT工艺参数对Al-Zn-Mg-Cu合金强韧化机理研究

针对A1-Zn-Mg-Cu合金进行了HPT变参数正交实验,以探讨HPT工艺参数对合金力学性能的影响。通过多角度力学性能测试,包括抗拉强度和延伸率等,与常温试件的力学性能进行了比对,分析了变化规律;利用SEM对A1-Zn-Mg-Cu合金在高温下的断口形态进行观察,以揭示高温高压下A1-Zn-Mg-Cu合金的破坏机制。研究内容将为该技术在工业上的推广与应用奠定一定的理论与技术基础。

熔体冲击法增材制造技术对高合金化Al-Zn-Mg-Cu合金组织的影响

利用直读光谱分析仪、金相显微镜、扫描电镜、能谱仪等检测设备,探究熔体冲击法增材制造高合金化Al-Zn-Mg-Cu合金铸锭的组织特性。研究结果表明:相比于浇铸铸锭,熔体冲击法获得的打印铸锭在高度方向上具有更均匀的成分;晶粒尺寸细小,晶粒形貌由树枝晶转变为等轴晶或等轴枝晶;主合金元素Zn、Mg、Cu的晶内固溶量明显提高,晶界上的第二相明显减少;在同样的均匀化退火温度下,打印铸锭可以在更短的时间达到理想的效果,从而可降低成本,提高生产效率。

Al-Zn-Mg-Cu系铝合金增材制造研究进展

Al-Zn-Mg-Cu系(即7xxx系)铝合金是军民两用最为广泛的一类超高强度铝合金,Al-Zn-Mg-Cu系铝合金增材制造技术具有复杂零件精密成形与轻量化设计等显著优势,市场需求广泛。本文综述了Al-Zn-Mg-Cu系合金增材制造技术的研究进展,总结了国内外增材制造7075铝合金目前存在的问题和改进措施。对7075铝合金增材制造技术未来的研究热点和发展方向进行了展望。

超高强Al-Zn-Mg-Cu系合金板材研究

利用金相显微镜、扫描电镜、拉伸试验机研究了超高Zn、Mg含量和微量Sc、Sm稀土元素对Al-Zn-Mg-Cu系合金板材微观组织和力学性能的影响。研究结果表明:板材强度随Zn、Mg元素含量的增加而提高;添加微量Sm元素对细化晶粒没有效果,且在基体中形成不能消除的含Sm第二相,对性能不利;Sc可有效细化铸锭晶粒,抑制再结晶,并显著提高板材强度,Sc元素添加量达到w(Sc)=0.2%可使板材屈服强度提升59 MPa,抗拉强度提升51 MPa;在高合金化的基础上复合添加w(Zr)=0.12%和w(Sc)=0.2%,板材屈服强度可达726 MPa,抗拉强度可达752 MPa。

纳米改性Al-Zn-Mg-Cu合金电弧熔丝增材成形工艺及组织和性能

采用电弧熔丝增材制造技术(WAAM)对纳米改性Al-Zn-Mg-Cu合金进行成形试验,分析了焊接电流、焊接速度、沉积路径、层间等待时间对成形性能的影响.结果表明,在焊接电流190 A、焊接速度350 mm/min、往复沉积、层间等待时间为90 s时合金具有良好的成形性能.对制备的直壁墙体进行了沉积后热处理,对不同状态合金的组织和性能进行了研究.沉积态及热处理态合金显微组织均具有优异的各向同性,由细小的、无明显取向的等轴晶组成.T6处理显著提高了沉积态合金的硬度及力学性能,T6处理后平均硬度为178.3 HV,较沉积态提升61%,沿横向抗拉强度(Rm)、屈服强度(R_(eL))与断后伸长率(A)分别为469.7(±5.1)MPa,366.3(±1.4)MPa与6.4(±0.4)%,沿纵向抗拉强度(Rm)、屈服强度(R_(eL))与断后伸长率(A)分别为454.3(±18.8)MPa,364.7(±16.7)MPa与5.9(±0.5)%,具有良好的力学性能各向同性.

Al-Zn-Mg-Cu-Zr合金的热变形行为研究

以7000系Al-Zn-Mg-Cu-Zr合金为研究材料,在Gleeble1500热模拟试验机上进行变形温度250~400℃,应变速率0.01~10 s^(-1)条件下的等温压缩试验。研究结果表明:合金在等温压缩过程中的流变应力随着应变速率的增大而增大,随着变形温度的增大而减小。当应变速率为10 s^(-1),变形温度为250℃时,合金的峰值应力可达205 MPa。大部分的真应力-应变曲线呈现动态再结晶特征,结合TEM分析,动态再结晶的形成机制是位错通过滑移和攀移逐渐演变成小角度晶界(2°~15°)和大角度晶界(>15°),依靠位错重排在原始晶粒内部形成亚结构,最终形成完整晶界。同时,采用Arrhenius模型和Zener-Hollomon参数方程,构建了Al-Zn-MgCu-Zr合金的本构方程,其中合金的平均变形激活能为324 187 J/mol。此外,通过Prasad失稳判据等模型,构建了0.2、0.4以及0.6应变下的Al-Zn-Mg-Cu-Zr合金的热加工图,获得可加工窗口为:252~400℃,0.01~0.015 s^(-1)。

超声振动对Al-Zn-Mg-Cu合金时效组织和性能的影响

基于自制的超声振动装置对Al-Zn-Mg-Cu合金进行超声振动时效,采用室温拉伸试验、显微硬度测试、电导率测试、金相显微镜和扫描电子显微分析(SEM)等手段,采用单因素实验设计研究超声振动时效时间和时效制度对Al-Zn-Mg-Cu合金组织与性能的影响。结果表明:施加超声振动促进析出相的生长,随着超声振动时效时间的延长,合金电导率逐渐升高,硬度和抗拉强度逐渐降低,伸长率略微增加。金相分析表明超声振动的激振应力切割粗大的第二相粒子,使得黑色颗粒变小,最后溶解或消失。施加超声振动对晶粒大小、形状和数量无明显影响。同时激振应力使得位错塞积开通,降低位错密度,降低残余应力。通过SEM显微镜对拉伸断口观察发现随着施加超声振动时间的延长,韧性断裂的特征更明显,韧窝数量显著增多,韧窝尺寸变大,深度变深。