基于人工神经网络的Mg-Zn-Zr-Ce合金热压缩变形研究

为研究含稀土元素铈的镁合金中高温流变行为,利用热模拟试验机对Mg-6Zn-0.5Zr-1.5Ce合金在变形温度523～673 K、应变速率0.001～1 s-1范围内进行热压缩实验.基于真应力真应变实验数据构建了单隐层前馈误差反向传播人工神经网络模型,利用该模型对ZK60-1.5Ce合金的流变应力行为进行预测,并分析了变形温度、应变速率与真应变对流变应力的影响.研究表明:Ce添加可显著细化晶粒;该镁合金的流变应力随变形温度降低和应变速率升高而增加;其流变应力行为可用双曲正弦函数进行描述,依据峰值应力拟合求得该合金的表观激活能为161.13 kJ/mol;变形温度和应变速率对流变应力的影响高于真应变.所建立的人工神经网络模型可以很好地描述该镁合金的流变应力,其预测值与实验数值吻合良好.

Microstructure and mechanical properties of high speed indirect-extruded Mg-5Sn-(1,2,4 )Zn alloys

The microstructural evolution and mechanical properties of high speed indirect-extruded Mg-5%Sn-(1, 2, 4) Zn(mass fraction, %) alloys were investigated by optical microscopy(OM), X-ray diffraction(XRD), scanning electron microscopy(SEM), differential thermal analysis(DTA) and a static tension tester. All the studied alloys can be extruded successfully at a high speed of 10 m/min. The grain size, area fraction of particles and tensile properties are found to be greatly affected by the extrusion speed and Zn content, resulting in tensile properties showing lower strength and ductility as the extrusion speed increases and Zn content decreases. The dependence of grain size and tensile properties on the second phase particles is also discussed.

Microstructure, texture and tensile properties of Mg-10Sn alloys extruded in different conditions

Indirect extrusion of Mg-10%Sn (mass fraction) alloys was performed at three different working temperatures. The effect of working temperature on the microstructure, texture and tensile properties of the extruded alloys was investigated by optical microscope (OM), scanning electronic microscope (SEM), X-ray diffraction (XRD) and a standard universal testing machine. Grain size, area fraction of second phase particles and texture of the alloys are found to be significantly influenced by working temperature. The grain size refinement is greatly dependent on processing conditions with the low working temperature being the most effective. While the high working temperature results in a coarser grain size and a stronger fiber texture and the reason for this phenomenon was examined in terms of second phase particle, grain type and dynamic recrystallization mechanism. Tested in the different conditions, the tensile strengths of the Mg-10Sn alloys extruded at the high working temperature are remarkably better than those of the other studied alloys. This significant improvement in tensile properties is mainly due to the particle strengthening and texture strengthening resulted from the more and finer primary dispersed particles and stronger texture, respectively.

反向挤压Mg-6Sn合金的组织、织构和拉伸性能与变形条件间的依赖关系(英文)

通过光学显微镜(OM)、扫描电子显微镜(SEM)、X射线衍射仪(XRD)和电子材料试验机研究了反向挤压Mg-6Sn合金的组织、织构和拉伸性能与挤压条件(挤压速度和初始坯料温度)间的依赖关系。研究结果表明:反向挤压Mg-6Sn合金的晶粒尺寸、再结晶体积分数和动态析出第二相体积分数在很大程度上取决于反向挤压参数,随着挤压速度和初始坯料温度的升高,合金的织构强度减弱。通过控制挤压速度和初始坯料温度,经高温挤压后的合金表现出最高的抗拉强度。对于商业AZ31镁合金而言,合金的强度随着挤压温度的升高而降低。本研究的Mg-6Sn合金经高温挤压后的抗拉强度和经低温挤压后的AZ31合金相当。上述研究结果表明Mg-6Sn合金是一种适合于高速度挤压的新型合金系。

超细晶反挤压Mg-8Sn-1Al-1Zn合金的组织和性能

采用OM、SEM、XRD、EBSD、TEM和电子材料试验机等手段研究了超细晶反挤压Mg-8%Sn-1Al-1Zn(质量分数)合金的组织和力学性能。结果表明:在250℃下,通过反挤压可以制备出具有超细晶组织的高强度Mg-8Sn-1Al-1Zn合金。在反挤压过程中,大部分粗大晶粒均通过动态再结晶转变为细小的等轴晶,其平均晶粒尺寸为1.92μm。另外,合金中存在大量的微米和纳米级Mg2Sn颗粒相。反挤压合金表现出典型的基面纤维织构。上述组织特征是动态再结晶、孪晶和第二相共同作用的结果。合金的室温抗拉屈服强度和压缩屈服强度分别为285和260MPa,合金的拉伸/压缩屈服点比率R高达0.91。合金的高强度和高R值主要归因于合金的细晶组织以及弥散分布的微纳米级第二相。