淬火介质对7055铝合金晶界析出行为的影响

采用透射电镜研究了淬火介质对7055铝合金晶界析出相及无沉淀析出带的影响。结果表明，空气淬火时，合金冷却过程在晶界上析出η平衡相。合金经室温水淬及沸水淬火合金时效后，晶界析出相尺寸差别小，呈链状连续分布；晶界无沉淀，析出带较窄，平均宽度分别约为33nm和43nm。空气淬火合金时效后晶界析出相尺寸差别较大，呈不连续分布；晶界无沉淀，析出带很宽，约102nm。对其原因进行了分析和讨论。     

Advanced HSLA Steels for Automotive Use

Characteristic HSLA steels for automotive use are introduced in which both of precipitation and microstructure is controlled to obtain suitable mechanical properties.For outer panels such as fender,the combination of low yield strength,high tensile strength and deep-drawability were realized by controlling the distribution of NbC and precipitation free zone.The other steel,developed for chassis parts such as lower arm,utilizes extremely fine interphase precipitation to obtain high yield strength and excellent hole expansionability.Both steels have contributed to the reduction of weight in car body.     

铝合金无沉淀析出带的研究进展

综述了过去50年来铝合金中无沉淀析出带(PFZ)的研究,重点论述了PFZ的主要形成机理、影响因素及其对合金性能(主要为力学性能和耐腐蚀性能)的影响,系统介绍了PFZ在形成机理及对合金性能上所持的不同观点及其相关理论。最后,提出了对铝合金中PFZ方面存在的难点以及重点研究方向。     

7475和7050铝合金PFZ的形成特点及其对性能的影响

利用透射电子显微镜分析了7475和7050铝合金经不同时效制度处理后的显微组织,并测试了不同状态下合金的常规力学性能及部分断裂韧性和合金的抗剥层腐蚀能力。结果表明,时效制度可明显改变合金的PFZ宽度,而对应于不同宽度的PFZ,合金有不同的性能。     

Al-Zn-Mg-Cu合金第二相粒子及其无析出区与晶界的作用过程研究

制备一种含Sc和一种含Cr、Mn、Ti、Zr的Al-Zn-Mg-Cu合金,采用透射电镜研究合金中第二相粒子周围的无析出微区和晶界上的无沉淀析出带及其相互的作用过程,给出单个第二相粒子对晶界作用力的方程.当驱使晶界迁移的动力大于粒子及其周围的无析出微区对晶界的阻碍作用时,晶界被粒子穿透而形成孔洞.在晶界扫过粒子的过程中,经历了先加速后减速两个阶段.晶界位于粒子直径区位置时所受的阻力最小、运动速度最大.当晶界能与相界能增量之和等于晶界运动的驱动力时,晶界被粒子钉扎而停止运动.在晶界迁移的过程中,溶质原子倾向于由高浓度区域向低浓度区域扩散,晶界和粒子周围的无析出区对晶界的迁移过程有明显的影响.     

Influence of γ′ and grain boundary carbide on tensile fracture behaviors of Nimonic 263

Tensile fracture behaviors of Nimonic 263 after three different heat treatments have been investigated. Standard heat treatment produces 10% γ′ coupled with precipitate free zones (PFZs), and M₂₃C₆ carbide densely distributed at grain boundaries (GBs). Alternative heat treatment causes dense distribution of GB carbides and precipitation of 1–3% γ′ with the absence of PFZs. Solution-treated sample has neither γ′ nor M₂₃C₆ carbide. Room temperature tensile tests indicate both standard and alternative heat-treated samples show intergranular fracture, but the elongation of the latter is two times larger than that of the former. The combined effect of GB carbides and intensive slip bands accounts for the intergranular fracture. The γ′ volume fraction affects elongation. Solution-treated sample displays transgranular fracture mode. Lack of restriction to dislocation mobility in grains interior and the weak interaction between GBs and dislocations are responsible for the transgranular fracture. The effect of PFZs on fracture mode may be negligible.     

原位合成Ni／Ni—Al金属间化合物层板复合材料的组织转变

在原位合成的Ｎｉ／Ｎｉ－Ａｌ金属间化合物层板复合材料中，随着退火温度升高，层状化合物相逐渐由富Ａｌ相转变为富Ｎｉ相。在层状的化合物相生长过程中晶界扩能占主导地位。经１１５０℃Ｎｉ退火的层中，离Ｎｉ３Ａｌ层近的区域，均匀形核的析出相生长的比较粗大，在Ｎｉ层中间，细小的析出相是非均匀形核的，在连续冷却过程中，晶界析出相通过晶界面扩散而长大的 同时，也造成了成晶界面两侧出现溶质的贫乏区，从而导致无析出带     

Physical metallurgy of aluminum-lithium alloys

The addition of lithium to aluminium reduces the density and increases the elastic modulus; precipitation of the metastableδ′(Al₃Li) phase from supersaturated Al-Li solid solution leads to appreciable increase in strength. The enhanced values for specific modulus and specific strength favour the use of the Al-Li alloys as structural materials for aerospace applications. However the binary alloys suffer from problems of poor ductility and toughness associated with strain localisation (resulting from the ease with whichδ′ particles are sheared during deformation), the presence ofδ′-free zones near grain boundaries and the heterogeneous nucleation of the equilibriumδ phase on the grain boundaries. These problems have been overcome by the development of ternary and quaternary alloys containing copper and magnesium. A small amount (∼0·1%) of zirconium is added to these alloys to improve the recrystallisation characteristics. The properties of alloys developed for commercial exploitation are briefly discussed. An overview of the physical metallurgy of the Al-Li alloys is presented with emphasis on the following features: (i) phase equilibria and precipitation reactions in Al-Li, Al-Cu-Mg, Al-Cu-Li and Al-Mg-Li systems and extension of these results to Al-Li-Cu-Mg alloys, (ii) insoluble particles and their effect on precipitation in the alloys, (iii) microstructural studies on Al-2·3%Li-1·2%Cu-0·7%Mg-0·12%Zr alloy, (iv) lithium depletion during solution treatment, (v) coarsening ofδ′ particles and development of precipitate-free zones near grain boundaries and (vi) microanalysis of the lithium containing phases.     

Stress corrosion cracking behavior of Al−Cu−Li−Mg−Zr(−Ag) alloys

The effect of aging on the stress corrosion cracking (SCC) behavior of Al−Cu−Li−Mg−Zr(−Ag) alloys such as Weldalite 049 and AA 8090 was studied by the constant elongation test method to investigate their SCC mechanism. The SCC resistance was not very sensitive under the strain rate of 2×10⁻⁵/sec, whereas it was significantly decreased under the strain rate of 5×10⁻⁶/sec. The SCC preferentially occurred in the intergranular crack mode. The relatively poor SCC resistance of Weldalite 049 in the under-aged condition was improved by aging. Considering the microstructural development during aging, it is related to the dissolution of the precipitation free zone as an anodic area and the strengthening by the coarsening of precipitation.     

Al-Ag合金γ相周围无沉淀带形成的机理研究

运用固体经验电子理论(EET)，对Al—Ag合金γ相的价电子结构以及γ相与基体的界面能进行了计算。结果表明，沉淀相与基体的界面处能量连续性较差，γ相的表面结合能高于基体的表面结合能，在界面处形成能量势阱。因此结合能大的γ相表面易吸附界面附近基体的Ag原子，引起γ相周围Ag原子的贫乏，出现γ相无沉淀带(PFZ)。