Effect of equal channel angular extrusion on the microstructure and superplasticity of an Al-Li alloy

This research investigates the use of equal channel angular extrusion (ECAE) processing to produce a superplastic form of the aluminum alloy 2098. The starting material was a hot-rolled and precipitation-hardened plate with elongated grains of width 67–92 μm, and a composition in weight percent of 2.2% Li, 1.3% Cu, 0.73% Mg, 0.05% Zr, balance Al. Microstructural evolution was investigated with optical and transmission electron microscopy (TEM) and microhardness measurements after each step of a multipass ECAE process. ECAE produced a submicron grain structure with an average size of about 0.5 μm. The sub-grain microstructure size was a function of the magnitude of the input strain and the extrusion temperature. Misorientation angles of the developed submicron structure increase with increasing number of passes at warm working temperatures. Superplastic behavior of the ECAE-processed alloy was achieved. However, the low zirconium content of the 2098 alloy resulted in grain growth of the refined structure at the superplastic processing temperatures, placing a lower limit on the deformation rates that can be used.     

SUPERPLASTICITY OF A SiC_w/2024 Al COMPOSITE MADE BY PRESSURE INFILTRATION

The superplastic characteristics of the β-SiC whisker reinforced 2024 aluminum composite, fabricated by pressure infiltration and hot-rolling after extrusion, were investigated. The composite has a fine grain size of about 1μm, and exhibits a maximum tensile elongation of 370% in the initial strain rate of 3.3×10-3s-1 at 788K.The superplastic deformation mechanism of the composite is thought to be grain boundary (interface) sliding accommodated by grain boundary diffusion of aluminum atom and an appropriate amount of liquid phase.     

Composite purification technology and mechanism of recycled aluminum alloys

Iron-rich inclusions in aluminum alloys can be effectively removed by composite purification of sedimentation and filtration technology. The results show that the purposed method has no negative effects on aluminum alloys and obviously improve their mechanical properties.     

Al-7.5Zn-1.5Mg-1.4Cu-0.15Zr7085铝合金挤压材的热处理制度

采用显微硬度与电导率测试、拉伸试验、晶间腐蚀及剥落腐蚀试验、金相(OM),研究了热处理制度对Al-7.5Zn-1.5Mg-l.4Cu-0.15Zr7085铝合金挤压材性能的影响.结果表明:常规固溶(470℃×2h)时效后合金的屈服强度与抗拉强度分别为458.5、522.5 MPa,而经强化固溶(470℃×2h+480℃×2h+490℃×2h)时效处理的合金为4523、517 MPa,表明固溶处理对合金的拉伸性能影响不大;时效制度对合金的硬度、电导率及抗腐蚀性能有较大影响.最后得出该成分合金的最佳热处理制度为强化固溶T76(121℃×5h+153℃×16h或121℃×5h+163℃×7h)时效处理,此时合金具有良好的综合性能,可以更好的运用于工业化生产.     

固溶处理工艺对7449铝合金组织和性能的影响

通过硬度、电导率、拉伸试验及金相分析,研究了在460、475、490℃分别保温30、60、120 min的固溶工艺对7449铝合金组织和性能的影响。结果表明,475℃×1 h是该合金最优的固溶工艺,此时合金的综合性能最佳;且固溶处理＋自然时效态合金的抗拉强度、屈服强度和伸长率分别为561．32 MPa、362．19 MPa、22．92％;合金的固溶处理过烧温度为490℃;在固溶处理中,固溶温度比保温时间对该合金性能的影响更大。     

铝合金搅拌摩擦焊异种焊接头的显微组织和力学性能

对8mm厚6082/5083铝合金进行了搅拌摩擦焊焊接,焊后通过金相分析、拉伸试验和断口形貌观察等方法研究了搅拌摩擦焊异种焊接头的显微组织和力学性能.研究结果表明:在旋转速度800 r/min、焊接速度120 mm/min工艺条件下,接头表面成形良好,内部无明显缺陷.焊核区是由细小的等轴晶组织构成;前进边和回转边的界面形态差异较为明显,前进边的组织形貌呈花纹状,由两种铝合金组织交互融合而成,但回转边组织形貌则呈曲线状,明显将两种组织分开.断口形貌分析显示,接头断裂模式为脆性断裂.     

铝合金壳体铸件翻转浇注工艺研究

翻转浇注是重力浇注的一种特殊形式,它有许多优点,有利于解决复杂铸件浇注过程产生的缩孔、缩松、气孔、夹杂等铸造缺陷.对航空用铝合金壳体铸件的浇注工艺进行了研究,分析了传统重力底注铝合金壳体铸造缺陷的原因,提出了翻转浇注工艺并进行了改进.结果表明,改进后的工艺使铝合金壳体铸件的合格率增至90％,获得了无夹渣和气孔的铸件.     

汽车发动机用6A02铝合金管材挤压速度仿真优化

如何实现6A02铝合金在汽车发动机上广泛使用对于汽车发动机发展有着重要作用.而合适的挤压速度范围是实现6A02铝合金管材挤压的关键因素之一.以6A02铝合金管材(φ29 mm×4.5 mm)挤压工艺过程为研究对象,基于DEFORM-2D软件模拟研究了挤压速度对载荷及模口坯料金属峰值温度的影响规律.获得了该规格6A02铝合金管材在250 kN挤压机上的合理挤压速度范围约为25～45 mm/s.     

铝合金激光拼焊应力场数值模拟

利用有限元分析软件ANSYS模拟铝合金激光拼焊时应力场的变化.选取的热源模型为高斯热源,利用ANSYS软件的APDL语言编写程序实现移动热源的加载.在模拟中不但要考虑一般激光焊接中参数对应力场的影响,还要考虑铝合金激光拼焊的特性.结果表明,在焊缝区工件处于拉应力状态,远离焊缝逐渐过渡到压应力状态.当激光功率3000～4500 W、焊接速度2～4 m/min时,随着激光功率增大和焊接速度降低,焊缝附近的拉应力峰值及应力分布范围增大.     

Al涂层对γ-TiAl合金高温抗氧化能力的影响

研究了多弧离子镀铝对γ-TiAl合金850℃、950℃恒温氧化性能的影响,同时分析讨论了镀铝层的氧化机制.结果表明:多弧离子镀铝后,形成的纯铝涂层均匀致密,无裂纹、孔洞,与基体结合良好.静态空气中,850℃氧化100 h后,形成了连续致密的Al2O3膜层及扩散层TiAl3相;950℃氧化100 h后,表面氧化膜由Al2O3及少量的TiO2组成,膜层中TiAl2为主要成膜相.多弧离子镀铝有效地提高了γ-TiAl合金高温抗氧化性能.