Na对Al—Mg—Li合金焊缝金属韧性的影响

研究了ＴＩＧ焊接时微量杂质元素Ｎａ对０１４２０Ａｌ－Ｍｇ－Ｌｉ合金焊缝金属力学性能的影响．Ｎａ含量小于２０μｇ／ｇ时，焊缝金属不发生脆化，含量达到５０μｇ／ｇ时，焊缝强度稍有下降，塑性急剧降低用电子探针分析发现Ｎａ在焊缝枝晶界偏聚．     

Al－Li－Cu－Mg－Zr合金的晶界断裂

本文通过室温拉伸试验，利用扫描电镜和透射电镜研究了Ａｌ－Ｌｉ－Ｃｕ－Ｍｇ－Ｚｒ合金不同时效状态下的拉伸性能和断裂行为。结果表明，该合金的力学性能与主要强化相δ＇（Ａｌ３Ｌｉ）的尺寸有关，其断裂行为决定于位错的共面滑移程度和滑移与晶界沉淀相的交互作用。     

Al—Li—Cu—Mg—Zr合金的晶界断裂

本文通过室温拉伸试验，利用扫描电镜和透射电镜研究了Ａｌ－Ｌｉ－Ｃｕ－Ｍｇ－Ｚｒ合金不同时效状态下的拉伸性能和断裂行为，结果表明，该合金的力学性能与主要强化相δ＇（Ａｌ３Ｌｉ）的尺寸有关，其断裂行为决定于位错的共面滑移程度和滑移与晶界沉淀相的交互作用。     

EFFECT OF Na ON PLASTICITY OF Al─Mg─Li ALLOY WELD METAL

研究了ＴＩＧ焊接时微量杂质元素Ｎａ对０１４２０Ａｌ－Ｍｇ－Ｌｉ合金焊缝金属力学性能的影响，Ｎａ含量小于２０μｇ／ｇ时，焊缝金属不发生脆化，含量达到５０μｇ／ｇ时，焊缝强度 肖有下降，塑性急剧降低，用电子探针分子分析探针分析发现Ｎａ在焊缝枝晶界偏聚。     

Al-Li-Mg-Si合金的相图计算及组织的TEM观察

分析了Ｌｉ加入Ａｌ－Ｍｇ－Ｓｉ体系后相的析出和组织变化,计算了几个典型的相图截面,并对三种典型合金进行了ＴＥＭ观测验证。相图计算表明,Ｌｉ加入Ａｌ－Ｍｇ－Ｓｉ体系后,在平衡状态下,δ为主要析出相,还形成富Ｓｉ相ＡｌＬｉＳｉ和Ｍｇ２Ｓｉ;在非平衡的实际析出状态下,亚稳相δ'成为主要析出相。δ'相的析出抑制Ｍｇ２Ｓｉ的形成。增加Ｍｇ含量可在一定程度上促进Ｍｇ２Ｓｉ的析出。     

快速凝固Al—Li—Mg—Cu—Zr合金粉末除气机制的研究

较系统地研究了不同除气温度及不同除气时间快速凝固Ａｌ－Ｌｉ－Ｍｇ－Ｃｕ－Ｚｒ合金粉末表面结构及氧化层的组成，探讨了除气过程中粉末表面的反应，从理论上揭示了ＲＳ Ａｌ－Ｌｉ合金粉末除气的规律及机制。     

SiC_w／Al－Li－Cu－Mg－Zr复合材料压铸工艺的研究

本文利用挤压铸造法成功制备了ＳｉＣ_ｗ／Ａｌ－Ｌｉ－Ｃｕ－Ｍｇ－Ｚｒ复合材料。采用化学分析、电子探针和扫描电镜等分析测试手段对材料进行化学分析和组织观察。结果表明，所获得的复合材料样品中晶须分布均匀，各合金元素含量均可控制在成分设计范围内。拉伸试验结果表明，ＳｉＣ_ｗ／Ａｌ－Ｌｉ－Ｃｕ－Ｍｇ－Ｚｒ复合材料具有较优异的综合拉伸性能。     

快速凝固Al－Li－Mg－Cu－Zr合金粉末除气机制的研究

较系统地研究了不同除气温度及不同除气时间快速凝固（ＲＳ）Ａｌ－Ｌｉ－Ｍｇ－Ｃｕ－Ｚｒ合金粉未表面结构及氧化层的组成，探讨了除气过程中粉未表面的反应，从理论上揭示了ＲＳＡｌ－Ｌｉ合金粉末除气的规律及机制。     

喷射沉积Al－2．15Li－1．28Mg－1．26Cu－0．10Zr合金的显微组织与拉伸性能EI

采用新型的喷射沉积快速凝固工艺制备了Ａｌ－２．１５Ｌｉ－１．２８Ｍｇ－１．２６Ｃｕ－０．１０Ｚｒ合金，对合金的显微组织与拉伸性能进行了研究。实验结果表明，沉积态实验合金组织为大量细小、均匀的等轴晶，经热挤压后晶粒呈“砖块”状形貌特征，在晶界上不易观察到破碎氧化物。时效析出不规则形状的δ＇相粒子、球壳状β＇－δ＇复合沉淀相及Ｓ＇相。喷射沉积Ａｌ－Ｌｉ合金经１９０℃／２０ｈ时效后达到峰时效状态，此时材料的综合性能最优（σ＿ｂ＝５２８ＭＰａ，σ＿（０．２）＝４２０ＭＰａ，δ＝１２％）。与粉未冶金Ａｌ－Ｌｉ合金相比，材料的塑性明显改善。     

喷射沉积Al－2．15Li－1．28Mg－1．26Cu－0．10Zr合金的显微组织与拉伸性能

采用新型的喷射沉积快速凝固工艺制备了Ａｌ－２．１５Ｌｉ－１．２８Ｍｇ－１．２６Ｃｕ－０．１０Ｚｒ合金，对合金的显微组织与拉伸性能进行了研究。实验结果表明，沉积态实验合金组织为大量细小、均匀的等轴晶，经热挤压后晶粒呈“砖块”状形貌特征，在晶界上不易观察到破碎氧化物。时效析出不规则形状的δ＇相粒子、球壳状β＇－δ＇复合沉淀相及Ｓ＇相。喷射沉积Ａｌ－Ｌｉ合金经１９０℃／２０ｈ时效后达到峰时效状态，此时材料的综合性能最优（σ＿ｂ＝５２８ＭＰａ，σ＿（０．２）＝４２０ＭＰａ，δ＝１２％）。与粉未冶金Ａｌ－Ｌｉ合金相比，材料的塑性明显改善。     

Mechanical and anisotropic behaviors of Mg–Li–Zn alloy thin sheets

This study examined the mechanical property and formability of the cold-rolled Mg–Li–Zn alloy sheets with two different Li contents. Uniaxial tension and press-forming tests were carried out at room temperature. The tensile properties and formability parameters were correlated with the forming limit diagrams. The test results indicated that the Mg–Li–Zn alloy with a Li content of 6 wt% exhibited reasonable strength levels with moderate fracture elongation and that it did not show good stretchability and drawability at room temperature. The alloy with a Li content of 9 wt% presented excellent ductility even at room temperature and the strength levels were somewhat inferior. From the analysis, it was found that formability of the alloy with a higher Li content of 9 wt% was superior compared to that of the alloy with a Li content of 6wt%. Moreover, the fracture surfaces of the press-formed samples were considered and studied under a scanning electron microscope (SEM). The results showed that the partly ductile and partly brittle fracture pattern was observed in the tension–tension strain condition for both the alloys.     

Effects of Ti addition on the microstructures and mechanical properties of the Al–Mn–Mg–RE alloy

The effects of higher Ti addition (near peritectic point) on microstructures and mechanical properties of a designed Al–Mn–Mg–RE alloy were investigated by optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and tensile tests, respectively. The results show that the addition of Ti refined grains evidently, meliorated the morphology and distribution of iron-rich phase, and hence improved the mechanical properties of the Al–Mn–Mg–RE alloy. The fracture mechanisms changed from brittle fracture to ductile fracture after extruding. The addition of Ti refined the constituent particles and resulted in deeper and more homogenized dimples of the tensile fracture surfaces.     

Mechanical and bio-corrosion properties of quaternary Mg–Ca–Mn–Zn alloys compared with binary Mg–Ca alloys

Binary Mg–xCa alloys and the quaternary Mg–Ca–Mn–xZn were studied to investigate their bio-corrosion and mechanical properties. The surface morphology of specimens was characterized by X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results of mechanical properties show that the yield strength (YS), ultimate tensile strength (UTS) and elongation of quaternary alloy increased significantly with the addition of zinc (Zn) up to 4 wt.%. However, further addition of Zn content beyond 4 wt.% did not improve yield strength and ultimate tensile strength. In contrast, increasing calcium (Ca) content has a deleterious effect on binary Mg–Ca alloys. Compression tests of the magnesium (Mg) alloys revealed that the compression strength of quaternary alloy was higher than that of binary alloy. However, binary Mg–Ca alloy showed higher reduction in compression strength after immersion in simulated body fluid. The bio-corrosion behaviour of the binary and quaternary Mg alloys were investigated using immersion tests and electrochemical tests. Electrochemical tests shows that the corrosion potential (E_corr) of binary Mg–2Ca significantly shifted toward nobeler direction from −1996.8 to −1616.6 mV_SCE with the addition of 0.5 wt.% manganese (Mn) and 2 wt.% Zn content. However, further addition of Zn to 7 wt.% into quaternary alloy has the reverse effect. Immersion tests show that the quaternary alloy accompanied by two secondary phases presented higher corrosion resistance compared to binary alloys with single secondary phase. The degradation behaviour demonstrates that Mg–2Ca–0.5Mn–2Zn alloy had the lowest degradation rate among quaternary alloys. In contrast, the binary Mg–2Ca alloy demonstrated higher corrosion rates, with Mg–4Ca alloy having the highest rating. Our analysis showed the Mg–2Ca–0.5Mn–2Zn alloy with suitable mechanical properties and excellent corrosion resistance can be used as biodegradable implants.     

不同应变率下MgAlZnY合金的拉伸性能与断口研究

利用材料试验机开展了室温拉伸实验,在0.001,0.1,0.6s-1不同应变率下,研究了Mg3Al1Zn2Y,Mg3Al2Zn2Y与Mg3Al6Zn2Y合金流动应力的应变率敏感性,其大小为Mg3Al2Zn2YMg3Al1Zn2YMg3Al6Zn2Y。基于分形理论和计算机图像处理技术,结合扫描电镜分析,研究了合金断裂特征,结果表明:合金在不同应变率拉伸下的断口分形行为显著,分形维数可将断口的韧脆性与形貌特征联系起来,分形维数越大,合金塑性相对越好,合金越倾向于延性断裂,断口形貌也越复杂;三种合金断裂特性的应变率敏感性大小为Mg3Al2Zn2YMg3Al6Zn2YMg3Al1Zn2Y,且表现出正负不同的应变率效应。     

Processability and mechanical properties of surface-modified glass-fibres/phthalonitrile composite and Al–Li alloy fibre-metal-laminates

In this study, newly developed fibre-metal laminates (Al-LiFMLs) were prepared by a lay-up process of a high-performance surface-modified glass fibres/phthalonitrile (GFs/PN) composite and Al–Li alloy. The results showed that varying the composite considerably affected the tensile properties of the Al-LiFMLs, as well as exhibiting enhancements over the properties of both the individual Al–Li alloys and GFs/PN composite constituents. For instance, when the number of composite layers varied from 6 to 14, the ultimate tensile strength of the Al-LiFMLs increased from 315 to 611?MPa. It was revealed that the failure mode displayed a more ductile behaviour (up to 20%) for all the developed Al-LiFMLs affected by the ductile fracture mode of the Al–Li alloy.     

The influence of cathodic hydrogen charging on the mechanical behaviour of Al-4Zn-1Mg alloy

The effect of cathodic charging on the mechanical behaviour of Al-4Zn-1Mg alloy was studied. Hardening of the Al-4Zn-1Mg alloy surface, due to the hydrogen absorption, was observed. The ultimate tensile stress of the charged aluminium alloy was noted to be a non-linear function of the charging current density. The cathodically charged aluminium alloy exhibited brittle transgranular fracture at the surface layer, whereas ductile intergranular fracture was observed at the deeper layers of the same alloy.     

Investigation on high-temperature mechanical properties of Al–7Si–0.6Mg alloy by wire + arc additive manufacturing

The room temperature and high temperature tensile properties of Al–7Si–0.6Mg alloy prepared by wire arc additive manufacturing have been investigated. The results show that the strengthening phase gradually coarsens and the eutectic silicon phase does not grow and agglomerate, meanwhile, the tensile strength and yield strength of the alloy gradually decrease with the increase of temperature. The high-temperature properties of the alloy are better than that of cast alloy. With the increase of temperature, the fracture of the alloy changes from ductile transgranular fracture to intergranular fracture.     

Mg/Zn/Al瞬间液相过冷连接界面的组织与性能研究

采用瞬间液相过冷连接方法对AZ31镁合金/锌中间层/5083铝合金进行连接,利用SEM、XRD、拉伸实验机和微观硬度计对结合界面的微观组织、力学性能进行了表征。结果表明,以锌作中间层,采用瞬间液相过冷连接可以实现AZ31镁合金与5083铝合金的有效连接,接头的最高抗拉强度可以达到38.5MPa,随着低温扩散保温时间的延长,扩散层厚度随之增加,接头的抗拉强度也随之升高;接头的拉伸断口属于脆性断裂,结合界面形成了MgZn2和少量的Mg17Al12金属间化合物;结合界面的微观硬度最高达170。     

Effect of Zn addition on the precipitation behaviors of Al–Mg–Si–Cu alloys for automotive applications

Effect of Zn addition on the precipitation kinetics and age-hardening response of Al–Mg–Si–Cu alloys was investigated by differential scanning calorimetry (DSC), hardness measurements, tensile tests and microstructural characterization. The results show that, compared with the Zn-free alloy, both the starting and peak temperatures in the DSC curve, and activation energy of β″ precipitation of Zn-added Al–Mg–Si–Cu alloy decrease significantly, corresponding to the greatly improved precipitation kinetics and age-hardening response, i.e., a hardness increment of 70HV after aging at 185 °C for 20 min. Moreover, the peak hardness and tensile properties can also be greatly enhanced after adding 3.0 wt% Zn even exhibiting a ductile fracture feature in the peak-aged state. No precipitates of the Al–Zn–Mg alloy system appear in the Zn-added Al–Mg–Si–Cu alloys after aging at 185 °C, and pre-β″, β″, and L precipitates are still the main precipitates in the two alloys after peak aging treatment. Finally, based on the microstructural evolution, a schematic diagram of precipitation in the Al–Mg–Si–Cu–Zn alloy is put forward, and the relationship between mechanical properties and microstructure is also established.     

The microstructure and mechanical properties of as-cast Mg–4Y/Nd–2Zn alloys

Optical microscopy, scanning electron microscopy, X-ray diffraction and tensile testing were performed to investigate the microstructure and mechanical properties of as-cast Mg–4Y/Nd–2Zn alloys. The results show that the secondary dendritic arm spacing for the Mg–4Y–2Zn alloy is smaller than that for the Mg–4Nd–2Zn alloy, and that X-Mg₁₂YZn or W-Mg₃Zn₃Nd₂ form in Mg–4Y/Nd–2Zn alloys. The lamellar X phase distributes at the grain boundary, pointing into the grains, whereas the rod-like W phase preferentially segregates at the triangle junction of the grain boundary. The greater grain boundary strengthening effect and the smaller fragmentation effect of the brittle eutectic phases leads to the as-cast Mg–4Y–2Zn alloy having better comprehensive mechanical properties. The fracture mechanism for as-cast Mg–4Y/Nd–2Zn alloys is quasi-cleavage fracture.