Solidification behavior of 6061 wrought aluminum alloy during rheo-diecasting process with self-inoculation method

The semisolid slurry of the 6061 wrought aluminum alloy was prepared by the self-inoculation method (SIM). The effects of the isothermal holding parameters on microstructures of rheo-diecastings were investigated, and the solidification behavior of 6061 wrought aluminum alloy during the rheo-diecasting process was analyzed using OM, SEM, EDS and EBSD. The results indicate that the isothermal holding process during slurry preparation has great effect on primary α(Al) particles (α₁), but has little effect on the microstructure of secondary solidification in the process of thin-walled rheo-diecasting. Nucleation is expected to take place in the entire remaining liquid when the remaining liquid fills the die cavity, and the secondary solidification particles (α₂) are formed after the process of stable growth, unstable growth and merging. The solute concentration of remaining liquid is higher than that of the original alloy due to the existence of α₁ particles, hence the contents of Mg and Si in α₂ particles are higher than those in α₁ particles.     

Mechanical properties and fracture behaviors on 6061 aluminum alloy under shear stress state

The mechanical properties and fracture behaviors of 6061 aluminum alloy were investigated by the tensile shear tests and in-situ tensile shear tests with tensile shear specimen devised. The results indicate that many slip bands parallel to tensile direction are produced on the surfaces of the specimens. With shear strain rates increasing, the shear yield stress and shear ultimate stress of 6061 aluminum alloy remain constant basically, but the shear fracture strain decreases obviously. The shear strain rates have no influence on the fracture surfaces. The grain boundaries of 6061 aluminum alloy are the weakest area and microcracks initiate at the grain boundaries parallel to tensile direction under shear stress. With the shear stress increasing, the microcracks extend and coalesce. The fracture of specimens is due to coalescence or shearing between the microcracks.     

6061铝合金TTP曲线的研究

通过分级淬火法获得了6061铝合金TTP曲线,计算了淬火敏感温度区间的淬火因子,结合淬火因子分析法预测了在不同淬火冷却速率条件下合金的硬度,并与实测值进行对比。结果表明:6061铝合金TTP曲线的"鼻尖"温度约为340℃,淬火敏感温度区间为220～455℃;合金硬度的预测值与实测值吻合较好,淬火因子分析法预测合金的性能具有较高的准确度;合金在淬火敏感温度区间220～455℃的淬火冷却速率大于16.2℃/s时,合金的硬度能达到最大硬度值的95%以上。     

不同应力状态下6061铝合金力学性能及断裂行为的研究

对不同缺口试样进行准静态拉伸,研究了6061铝合金在不同应力状态的力学性能和断裂行为。研究结果表明,随着缺口半径增大,三轴应力度降低。随着三轴应力度降低,合金的峰值载荷降低,断面收缩率和断裂应变均增大,断口上剪切唇区面积逐渐增大,纤维区的山脊状的锯齿数量逐渐减少,但深度增加,显微断口上的韧窝越来越均匀细小。     

Titanium-zirconium-phosphonate hybrid film on 6061 aluminum alloy

Three titanium-zirconium-phosphonate hybrid films were formed on AA6061 aluminum alloy by immersing in fluorotitanic acid and fluorozirconic acid based solution containing different phosphonic acids for protective coatings of aluminium alloy.The corrosion resistance of three hybrid films as the substitute for chromate film were evaluated and compared.The neutral salt spray test was explored,the immersion test was conducted and electrochemical test was also executed.The hybrid films exhibited well-pleasing c...     

6061铝合金搅拌摩擦焊工艺

采用搅拌摩擦焊方法对板厚6mm的6061铝合金板在不同参数下进行焊接,研究6061铝合金搅拌摩擦焊工艺以及主要参数对焊缝成形和接头力学性能的影响,观察焊接接头的金相组织,通过硬度分布测试分析焊接接头的力学不均匀性.结果表明:压入量过大或过小时容易造成焊接接头成形差等缺陷,压入量为0.3 mm时可以获得优质的焊缝成形;搅...     

GH742y合金凝固偏析行为

采用组织分析和差热分析相结合的方法系统研究GH742y合金的凝固偏析行为和铸态组织形成规律。GH742y合金枝晶偏析严重,组织析出复杂:Cr、Co、W、V和Al偏析于枝晶干,而Nb、Ti和Mo等元素在枝晶间的富集导致一次和二次γ′相、(γ γ′)共晶、MC碳化物、M6C碳化物、Laves相和δ相的析出;稀土元素La和Ce的偏析导致Ni5Ce相和富氧硫稀土相的枝晶间析出。相分计算表明,严重的元素偏析以及大量富Nb和Ti相的析出是σ相和μ相等有害TCP相析出的主要原因。GH742y合金的凝固顺序为:γ基体、MC碳化物、一次γ′相、(γ γ′)共晶、Laves相、Ni5Ce相和M6C碳化物。     

挤压态6061铝合金的力学性能及显微组织

对挤压态6061铝合金分别进行了固溶处理和时效处理,采用万能试验机测试了其力学性能,通过SEM和TEM表征了合金的微观组织,研究了不同热处理条件下挤压态6061铝合金的组织演变规律。结果表明:固溶和时效处理后的挤压态6061铝合金均表现出明显的力学性能各向异性,且时效处理能有效提升合金的强度;同时,经时效处理后的挤压态6061铝合金表现出应变速率敏感性,而固溶处理的挤压态6061铝合金则无明显的应变速率敏感性;固溶处理和时效处理的挤压态6061铝合金的晶粒形态为等轴晶,但是有大小两种晶粒尺寸等级,大晶粒尺寸可达200 μm,小晶粒尺寸则小于10 μm。固溶和时效处理的挤压态6061铝合金均由较强的{001}<100>立方织构和较弱的{011}<100>高斯织构组成,且种类和强度相同;拉伸变形后的6061铝合金出现了大量的位错堆积,而经时效处理的合金中均匀分布短棒状的析出相能有效阻碍位错的运动,提高材料的变形抗力。     

Corrosive wear behavior of 2014 and 6061 aluminum alloy composites

Alloys of 2014 and 6061 aluminum reinforced with 0.1 volume fraction of alumina particles (VFAP) were subjected to impact scratching during a corrosive wear process. The transient currents generated due to the impact were measured in the two composites as well as in their respective monoliths. The effect of solutionizing time on the transient currents was correlated to the near surface microstructures, scratch morphology, concentration of quenched-in vacancies, and changes in grain sizes. It was observed that the transient current values increase with an increase in solutionizing time, indicating that the corrosive wear behavior is not strongly affected by the grain boundaries. However, a combination of pitting and the galvanic corrosion may account for the typical corrosive wear behavior exhibited by the alloys and the composites of this study.     

6061铝合金双轴肩搅拌摩擦焊接扭矩特征

为了揭示6061铝合金BTFSW过程中焊接扭矩的特征,对扭矩进行了检测,分析了扭矩信号的频谱特征、扭矩峰值的变化特点、扭矩振荡与焊缝表面成形的关系.研究表明扭矩具有周期性,主要频率接近于2倍主轴旋转频率值,频差的存在说明了焊接区域存在搅拌头与不同速率的金属流之间挤压摩擦的叠加行为;当接触点温度小于500℃时,扭矩峰值随着焊接速度的提高而变大,随着旋转速度的提高而变小;正常较小的扭矩振荡不影响表面成形,但当接触点温度大于550℃、上下轴肩间距过小或焊接速度过小或旋转速度过大等时,扭矩易发生异常振荡.对进一步揭示深入研究BTFSW焊接机理、搅拌头三维受力特征及其与焊接参数、焊接质量的关系有着重要的推动意义.     

6061铝合金板料的成形性能及数值模拟研究

通过单向拉伸试验获得了6061铝合金原始T6态和退火态板材的基本力学性能,进而得出了6061铝合金的真实应力应变曲线。在此基础上,用不同本构方程对实验数据进行拟合,然后与材料应变硬化曲线相比较。结果表明,采用含有幂函数的本构方程对两种状态的板材试验数据拟合较好,基于单向拉伸试验获得两种状态板材在真应变为8%时的塑性应变比分别为0.996和0.712。此外,用有限元软件Dynaform对6061铝合金管材进行绕弯模拟,对获得的成形性能参数进行了验证。     

喷射成形6061铝合金的热处理工艺

对喷射成形6061铝合金的热处理工艺进行研究,采用硬度测试、拉伸试验和透射电镜等研究固溶温度、时效温度和时效保温时间对合金显微组织和力学性能的影响规律。结果表明:随固溶温度的升高,合金硬度也随之升高,而其抗拉强度、屈服强度和断后伸长率则先增大后减小;合金硬度、抗拉强度和屈服强度随时效温度的升高先增大后减小,断后伸长率却一直减小;合金硬度、抗拉强度和屈服强度曲线随时效温保温时间的延长呈驼峰状变化,断后伸长率则变化不大,只在17 h时有所增大;喷射成形6061铝合金的最佳热处理工艺为530℃固溶1 h+175℃时效8 h。     

硼酸铝晶须增强6061铝合金复合材料的断口分形分析(英文)

硼酸铝晶须增强6061铝合金基复合材料中的界面反应影响其断口分形维数。该复合材料由压力铸造法制备,采用垂直剖面法分析拉伸断裂断口。当量尺度分别取3-15μm以及1-5μm时,可以在断口上发现分形现象。当量尺度在3-15μm的分形域,其分形维数与材料抗拉强度显著正相关。实验结果表明,随热处理时间的延长,界面反应产物的分布与状态可以改变材料的微观断裂模式,进而影响断口的粗糙度和分形维数,同时决定材料的抗拉强度。而当量尺度为3-15μm的分形域,其分形维数受热处理程度的影响不很显著。     

6061铝合金高温流变行为

利用Gleeble-3500热模拟实验机,对6061铝合金在变形温度为350℃、400℃、430℃、460℃、480℃和500℃,应变速率为0.001s-1、0.01s-1、0.1s-1、1s-1和10s-1条件下进行高温压缩实验,得到的真应力-真应变曲线形态基本符合铝合金的热变形力学特征。采用Arrhenius双曲正弦关系描述6061铝合金的高温流变行为,确定其激活能Q=163.4366kJ·mol-1;基于动态材料模型理论绘制6061铝合金热加工图,确定其最佳热加工区域温度为T=420℃~450℃。     

Laser welding of 6061 aluminum alloy sheet with surfactant

Aluminum alloy shows low absorption to laser for its essential high reflection property.In this paper,an active laser welding process is adopted to weld 6061 aluminum alloy with the halide surfactant c...     

6061铝合金冲击载荷作用下的变形断裂行为

利用常见的落锤冲击试验机和自行设计的夹具装置,研究6061铝合金材料在冲击载荷作用下的变形断裂行为。结果表明:6061铝合金受冲击载荷时的断裂行为与准静态拉伸相比无明显变化,损伤形式仍是由晶界处的微孔洞连接形成微裂纹,宏观上仍产生明显颈缩,试样的断裂面与拉伸轴方向大约成45°角。摆锤高度不同,试样表面的变形带不同,摆锤高度为141°时,出现了"白色变形带"。微观断口是由韧窝组成,冲击速度越大,韧窝越小。     

Solidification crack susceptibility of aluminum alloy weld metals

The susceptibilities of the three aluminum alloys to solidification crack were studied with trans-varestraint tests and tensile tests at elevated temperature. Their metallurgical characteristics, morphologies of the fractured surface and dynamic cracking behaviors at elevated temperature were analyzed with a series of micro-analysis methods. The results show that dynamic cracking models can be classified into three types. The first model has the healing effect which is called type A. The second is the one with deformation and breaking down of metal bridge, called type B. The last one is with the separation of liquid film along grain boundary, called type C. Moreover, the strain rate has different effects on crack susceptibility of aluminum alloys with different cracking models. ZL101 and 5083 alloys belong to type A and type C cracking model respectively, in which strain rate has greater effect on eutecfic healing and plastic deformation of metal bridge. 6082 alloy is type B cracking model in which the strain rate has little effect on the deformation ability of the liquid film.     

6061铝合金表面电弧喷涂纯铝涂层的研究

采用电弧喷涂技术在6061铝合金基材表面制备纯铝涂层.利用金相显微镜、扫描电镜、X射线衍射仪对其显微组织结构、涂层形貌、腐蚀产物、孔隙率进行了分析.采用电化学试验、浸泡试验、中性盐雾试验检测了涂层在w(NaCl)=5%的溶液中的耐腐蚀性能.研究结果表明,在铝合金基材表面能够获得组织均匀致密,低孔隙率的纯铝涂层,涂层与基体为机械嵌合,涂层封孔处理后,试样的耐蚀性能有很大提高,涂层对基体无阴极保护作用.     

Surface grain structure evolution in hot rolling of 6061 aluminum alloy

During hot deformation of Al–Mg–Si alloys, a non-uniform microstructure is developed due to differences in localized strain. Physical simulations were performed to examine the effects of processing parameters such as deformation temperature, total reduction, rolling schedule and alloying additions on the grain structure evolution. Overall, the kinetics of recrystallization followed the traditional trends predicted by JMAK kinetics. Electron backscatter diffraction (EBSD) was used to quantify the difference in recrystallization kinetics at the sample surface and mid-thickness. The results showed that the surface showed elevated kinetics when compared to the sample mid-thickness.     

6061铝合金搅拌摩擦焊接头组织及性能

对厚度6 mm的6061铝合金进行了搅拌摩擦焊对接焊,采用光学显微镜、扫描电子显微镜、拉伸试验机及电化学工作站等设备对焊接接头的金相组织、断口形貌、拉伸性能和腐蚀性能进行了测试和分析。结果表明,当焊接速度为80 mm/min、旋转速度在600～1 500 r/min之间时,焊接接头的外观良好,无明显缺陷。随着旋转速度的增加,焊核区晶粒呈现出先减小后增大的现象。当旋转速度为1 200 r/min时,焊核区的晶粒最细小,焊接接头的抗拉强度和断后伸长率最高,分别为168 MPa和14.7%,焊缝强度达到了母材的81.9%,焊接接头的断裂形式为以韧性断裂为主的韧-脆混合断裂模式。随着旋转速度增大,搅拌摩擦焊接头的耐腐蚀性能呈现先上升后下降的趋势,当搅拌头旋转速度为1 200 r/min时,焊接接头的耐腐蚀性能最好,其腐蚀电流密度最小为2.4×10-5 A/cm2。创新点： 研究了旋转速度焊接工艺参数与搅拌摩擦焊焊接头耐腐蚀性能之间的关系。