具有盘／片状，棒／针状析出相铝合金的时效—屈服强度变化模型

以析出热力学、长大动力学及强化理论为基础，研究了具有盘／片状、棒／针状析出相铝合金在时效过程中的析出相尺寸、体积分数变化及其对时效合金强化效果的影响，得到了合金成分、时效参数与组织参数、屈服强度间的解析关系式，进而从微观—宏观相结合的角度建立起了具有盘／片状、棒／针状析出相铝合金的时效工艺—屈服强度量化模型，并将该模型应用于6061合金和Al—Zn—Mg合金的时效性能预测，取得了较满意的结果。同时，详细讨论了析出相长径比对时效温度以及合金处理状况的依赖关系。     

铝合金中盘/片状,杆/棒状析出相的形状演变及动力学研究（英文）

微观组织定量化研究对于建立金属材料组织和性能关系有重要意义。研究了可时效强化铝合金中时效过程中析出相形状的演变和动力学过程,结合过饱和固溶体析出相变过程的经典理论、析出相生长过程的软碰撞理论和HHC理论,建立了具有盘/片状、杆/棒状析出相铝合金的析出相形状因子模型。并利用Al-Cu-Li-Zr合金T相、Al-Cu-Mg合金S相及Al-Mg-Si合金β相的析出相尺寸随时效时间变化的实验数据对模型进行验证,拟合的结果符合盘/片状、杆/棒状析出相随时效时间延长,析出相尺寸形状因子先急剧增大至极大值、再缓慢减小最终趋于稳定的一般规律,证实了模型的适用性和准确性。     

铝合金中盘/片状,杆/棒状析出相的形状演变及动力学研究

微观组织定量化研究对于建立金属材料组织和性能关系有重要意义。本文研究了可时效强化铝合金中,时效过程中析出相形状的演变和动力学过程,结合过饱和固溶体析出相变过程的经典理论、析出相生长过程的软碰撞理论和HHC理论,建立了具有盘/片状、杆/棒状析出相铝合金的析出相形状因子模型。并利用Al-Cu-Li-Zr合金T相、Al-Cu-Mg合金S相及Al-Mg-Si合金β相的析出相尺寸随时效时间变化的实验数据对模型进行验证,拟合的结果符合盘/片状、杆/棒状析出相随时效时间延长,析出相尺寸形状因子先急剧增大至极大值、再缓慢减小最终趋于稳定的一般规律,证实了模型的适用性和准确性。     

6061铝合金时效工艺和动力学模型研究

采用硬度测试、拉伸试验、TEM分析等手段,系统研究了不同时效温度和时间对6061铝合金型材力学性能的影响,并拟合了6061铝合金的时效动力学模型。结果表明,6061铝合金硬度到达到时效峰值的时间随时效温度的升高而缩短,并且硬度峰值随温度升高而降低;时效工艺为180℃9 h时,合金的硬度、屈服强度和抗拉强度达到峰值。结合TEM分析得知,合金的析出强化相为针状β″相;通过回归分析,在Johnson-Mehl-Avrami(JMA)方程的基础上建立了6061铝合金的时效动力学模型。     

后时效对超细晶6061铝合金微观结构与力学性能的影响

采用TEM、XRD、显微硬度实验和拉伸实验，利用等通道转角挤压(ECAP)和后时效相结合制备出超细晶6061铝合金，对其微观结构和力学性能进行了对比研究。结果表明，经过两道次ECAP后，合金的平均晶粒尺寸细化到210 nm。两道次ECAP+80℃、20 min低温后时效，合金的平均晶粒尺寸为278 nm，基体中弥散分布细小的针状β’’、L相和Q’相纳米级析出物，拉伸强度和屈服强度分别达到514和483 MPa，并保持了15.1%的均匀伸长率。ECAP在基体中引入的大量位错促进了析出相的形核，加速了时效过程中的析出动力学；ECAP低温后时效，合金的高强度和高韧性与细晶强化、位错强化和纳米析出相强化有关。基于实验结果，分析了合金ECAP和后时效过程中时效相的演变过程。     

时效工艺对Ti-26合金棒材组织和拉伸性能的影响

对经过790℃固溶处理后的Ti-26合金棒材进行了不同温度及时间的时效处理，研究了时效温度和时间对Ti-26合金棒材显微组织和拉伸性能的影响。研究结果表明：在450-550℃范围内，随时效温度升高，合金组织有针状“相弥散物析出。升温至510℃，相同时效时间内析出α相数量最多，高于510℃，部分析出α相开始溶解。合金时效处理10h内，随时效时间延长，合金组织针状α相弥散物数量增加，且针状α相存在跨晶界长大现象。合金经510℃×10h时效处理，OL相形核和长大达到最佳匹配，Ti-26合金获得理想的强度和塑性匹配。     

多重时效析出第二相对Al-Mg-Si合金电导率的影响

电导率的变化能够灵敏地反应Al-Mg-Si合金的时效析出过程,然而溶质原子及时效析出第二相对电导率的单独影响尚不清楚。Al-Mg-Si合金中含有3种成分和形貌不同的第二相。通过实验及模型化系统地研究Al-Mg-Si合金中多重析出第二相对其电导率的影响。结果表明:由于棒状β″相或针状β′相能够分别在473和523 K时有效地阻碍传导电子的移动,因此Al-Mg-Si合金的电导率主要依赖于棒状β″相(T=473 K)或针状β′相(T=523 K)的影响。模型预测结果与实验结果吻合良好,验证了模型的有效性。     

Al-Mg-Si合金中针棒状析出相时效析出动力学及强化模拟研究

通过与计算相图数据库相耦合,建立了Al-Mg-Si三元合金体系中针棒状析出相时效析出动力学和时效强化模型,考虑了析出相形貌对形核、生长、粗化以及强化效果的影响.通过该模型可以获得不同时效工艺下析出相微观组织特征参数的变化及对应的屈服强度变化.利用该模型模拟了Al-Mg-Si合金在不同时效工艺条件下的时效析出过程和屈服强度变化,并与实验结果及Lifshitz-Slyozov-Wanger粗化模型计算结果进行了对比.基于模型研究并分析了析出相长径比、界面能、合金元素含量以及析出相成分对Al-Mg-Si合金时效析出动力学和强化效果的影响.结果表明:不同的界面能和长径比会影响形核密度和析出相尺寸,进而影响合金的屈服强度.增加基体中Mg含量可以促进时效析出,提高合金屈服强度,而基体中Si含量的增加对合金屈服强度并不产生明显影响.     

纳米Al2O3P/6061铝基复合材料时效硬化特性的研究

探讨了不同纳米氧化铝颗粒含量、不同时效温度对纳米Al2O3P／6061铝基复合材料时效硬化行为的影响，结果发现，因强化相颗粒与铝合金基体的热膨胀系数差异．提供了析出物形成与成长的驱动力，导致其峰时效时间随强化相颗粒含量的增加及时效温度的升高而缩短，但其峰时效硬度会因时效温度提高使得析出物过度成长而随之降低。复合材料因受强化相与基体材料热膨胀系数的差异、强化相造成的铝合金晶粒细化以及强化相颗粒分散强化等三项因素影响，其硬度值随强化相颗粒增加而提高。     

时效对小变形量2A14铝合金微观组织的影响

通过透射电镜研究了时效对小变形量2A14铝合金微观组织的影响。研结果表明：小变形量的2A14铝合金在150 ℃时效4 h,合金中基本上没有析出或析出相的含量很少,时效10 h,合金中形成了少量的片状析出相Ω相和S'相。随着时效温度的升高和时效时间的延长,合金中析出的S'相的含量增加且尺寸增大,没有观察到Ω相。在180 ℃时效4 h,在位错上开始析出点状的S相,随着时效温度的升高和保温时间的延长,位错上析出的S相增多且尺寸增大,位错线变得不明显。晶界上的析出相主要是S相,在晶界附近没有观察到明显的无析出带。     

Effect of Different Scale Precipitates on Corrosion Behavior of Mg–10Gd–3Y–0.4Zr Alloy

A large amount of directional and willow-like β' phase was precipitated in Mg-10 Gd-3 Y-0.4 Zr(GW103 K) alloy after solution treatment and subsequently aged treatment(T6). In order to explore the effect of the precipitates on the corrosion behavior of the GW103 K alloy, the alloy was subjected to solution treatment(T4) at 773 K for 4 h at first, subsequently aged at 498 K for 193 h(T6). The microstructure evolution of the GW103 K alloy after this treatment was investigated by scanning electron microscopy and transmission electron microscopy. The high-angle annular detector dark-field scanning transmission electron microscopy was used to observe the typical corrosion morphologies of the nanoscale precipitation phases(β') in the T6-treated alloy. The corrosion rate was measured by potentiodynamic polarization test. Combining with the potential measurement results by scanning Kelvin probe force microscopy, the effects of the skeleton-like Mg_(24)(Gd,Y)_5 andf precipitates on the corrosion behavior of GW103 K alloy were explored. The results showed that the corrosion rate of the GW103 K alloy in different conditions was ranked as: as-cast alloy T4-treated alloy T6-treated alloy,attributing to the fact that the relative potential differences of skeleton-like Mg_(24)(Gd,Y)_5 were lower than those of the matrix, therefore Mg24(Gd, Y)5 phase formed micro-galvanic coupling with the matrix and corrosion dissolution occurred.The nanoscale β' precipitates in T6-treated alloy can retard the cathodic process.     

Precipitation of Icosahedral Quasicrystalline Phase, R-phase and Laves Phase in Ferritic Alloys

Ferritic heat resistant steels involving precipitation of intermetallic phases have drawn a growing interest for the enhancement of creep strength, while the brittleness of the intermetallic phases may lower the toughness of the alloy.Therefore, it is necessary to optimize the dispersion characteristics of the intermetallics phase through microstructural control to minimize the trade-off between the strength and toughness. The effects of α-Fe matrix substructures on the precipitation sequence, morphology, dispersion characteristics, and the stability of the intermetallic phases are investigated in Fe-Cr-W-Co-Si system. The precipitates of the Si-free Fe-10Cr-I.4W-4.5Co (at%) alloy aged at 873K are the R-phase but those of the Si-added Fe-10Cr-1.4W-4.5Co-0.3Si (at%) alloy are the icosahedral quasicrystalline phase. The precipitates in both the Si-free and Si-added alloys aged at 973K are the Laves phase. Matrix of the alloys is controlled by heat treatments as to provide three types of matrix substructures; ferrite, ferrite/martensite mixture and martensite. The hardening behavior of the alloys depends on the matrix substructures and is independent of the kinds of precipitates. In the alloys with ferrite matrix, the peak of hardness during aging at 873K shifts to longer aging time in comparison with that in the alloys with lath martensite matrix which contain numbers of nucleation sites.     

Effect of Aging on Superelastic Behaviors of a Metastable β Ti-Mo-based alloy

Effect of aging on the tensile and superelasticity (SE) behaviors of Ti-9.8Mo-3.9Nb-2V-3.1Al (wt.%) alloy have been investigated. It is found that the ultimate tensile strength (UTS) and yield strength of aged alloy change with the aging temperature following a nonlinear relationship due to ω-phase and α-phase precipitates. The SE, especially elastic recovery behavior, is closely related with the morphology of α-phase precipitates, as well as ω-phase formed during aging. At a maximum tensile strain of 4%, the specimen aged at 673 K with ω + α-phase precipitates shows a superelastic recovery strain of 3.2%. Lots of α-phase precipitates, distributing homogeneously in specimen aged at 773 K, result in the lost of SE. A maximum recovery strain of 3.3% is obtained for specimens aged at 873 or 973 K for 30 min, with coarse short bar-like α-phase precipitates.     

固溶处理及时效对镍钛形状记忆合金组织演化及力学性能的影响

将镍钛形状记忆合金Ni50.9Ti49.1（摩尔分数）在1123 K固溶处理2 h,然后分别在573、723和873 K时效2h。采用透射电镜、高分辨率透射电镜、扫描电镜和压缩实验,系统研究固溶处理和时效对镍钛合金组织演化及力学性能的影响。结果表明：固溶处理有助于消除原始镍钛样品中的Ti2Ni相,但不能消除TiC相。固溶处理导致镍钛合金中原子排列的有序畴界。在所有时效镍钛样品中,Ni4Ti3析出相、R相和B2奥氏体相共存于室温下的镍钛基体上,然而在873 K时效的镍钛样品中,可以观察到马氏体孪晶。在573和723 K时效的镍钛样品中,细小密集的Ni4Ti3相均匀分布在镍钛基体上,而且与B2基体保持共格关系。然而,在873 K时效的镍钛样品中, Ni4Ti3相尺寸非常不均匀,和B2基体保持共格、半共格和非共格关系。在723 K时效的条件下,细小均匀的Ni4Ti3相阻碍位错运动,导致最大的位错滑移临界分切应力,因此镍钛样品表现出最高的屈服强度。     

Revisiting the Hierarchical Microstructures of an Al-Zn-Mg Alloy Fabricated by Pre-deformation and Aging

Pre-deformation before aging has been demonstrated to have a positive effect on the mechanical strength of the 7N01 alloy in our previous study, which is rather different from the general negative effects of pre-deformation on high-strength 7XXX aluminum alloys. In order to explain the strengthening mechanism relating to the positive effect, in the present study, the microstructure of the aged 7N01 alloy with different degrees of pre-deformation was investigated in detail using advanced electron microscopy techniques. Our results show that, without pre-deformation, the aged alloy is strengthened mainly by the η′ type of hardening precipitates. In contrast, with pre-deformation, the aged alloy is strengthened by the hierarchical microstructure consisting of the GP-η′ type of precipitates formed inside sub-grains, the η_p type of precipitates formed at small-angle boundaries, and the dislocation introduced by pre-deformation (residual work-hardening effect). By visualizing the distribution of the η_p precipitates through three-dimensional electron tomography, the 3D microstructures of dislocation cells are clearly revealed. Proper combinations of η_p precipitates, GP-η′ precipitates and residual dislocations in the alloy are responsible for the positive effect of pre-deformation on its mechanical properties.     

Mg-8Zn-4Al-1Ca合金的时效微观组织(英文)

利用TEM和HRTEM研究Mg-8Zn-4Al-1Ca合金的时效微观组织。结果表明:Mg-8Zn-4Al-1Ca合金较Mg-8Zn-4A1合金时效硬度显著增高。Mg-8Zn-4Al-1Ca合金在160°C时效16 h,有大量的盘状Ca2Mg6Zn3相沉淀弥散析出,此外,合金的微观组织中还存在晶格畸变、蜂窝状的莫尔条纹、刃型位错及位错环;经48 h时效后合金中沉淀相为粗大的盘状沉淀相和细小、弥散的粒状沉淀相;经227 h时时效后后,其组织中存在大量MgZn2相和Ca2Mg6Zn3相。因此,在Mg-8Zn-4Al-1Ca时效160°C的合金中添加Ca元素能有效提高合金的时效硬度及促进MgZn2强化相的生成。     

具有盘状析出相铝合金的时交强化模型

以析出热力学、长大动力学及强化理论为基础,研究了具有盘状析出相的铝合金在时效过程中的析出相尺寸、体积分数变化及其对时效合金强化效果的影响,得到了合金成分、时效参数与组织参数、屈服强度间的解析关系式,进而从微观与宏观相结合的角度建立起了具有盘状析出相铝合金的时效工艺－屈服强度量化模型,并将该模型应用于Al-Cu二元系列合金的时效性能预测,取得了较满意的结果。同时,由数据的归纳和组合得出了Al-Cu二元系列合金中盘状析出相临界形核能垒的简易求解式f（△G,x0/xc）＝常数,有助于该模型的普遍适用化。     

AA 7055铝合金时效析出强化模型

利用小角度X射线散射技术获得的系列定量信息,综合运用时效析出动力学理论和析出相切过、绕过强化机制,研究了AA 7055铝合金在120和160℃时效过程中的屈服强度演变模型。结果表明,在时效早期盘状析出相的盘面半径和半厚度均与t^1/2(t为时效时间)成线性关系;在时效后期,析出相尺寸则与t^1/3成线性关系。时效过程中析出相体积分数与t的变化关系遵循JMA (Johnson-Mehl-Avrami)型表达式。综合考虑了GPI区和η’相2类析出相对合金强度的贡献,并且分别考察了这2类析出相的模量强化机制和共格应变强化机制,最终建立了AA 7055铝合金在120和160℃时效过程中的屈服强度变化模型,确定了该合金时效过程中析出相与屈服强度之间的定量关系。     

Dynamics of phase transformation of Cu-Ni-Si alloy with super-high strength and high conductivity during aging

The precipitation behaviors of the Cu-Ni-Si alloys during aging were studied by analyzing the variations of electric conductivity.The Avrami-equation of phase transformation kinetics and the Avrami-equation of electric conductivity during aging were established for Cu-Ni-Si alloys,on the basis of linear relationship between the electric conductivity and the volume fraction of precipitates,and the calculation results coincide well with the experiment ones.The transformation kinetics curves were established to characterize the aging process.The characteristics of precipitates in the supersaturated solid solution alloy aged at 723 K were established,and the results show that the precipitates areβ-Ni3Si andδ-Ni2Si phases.