阻尼镁合金的研究现状与发展趋势

阐明了镁合金的阻尼机理及应变振幅、频率、温度对镁合金阻尼性能的影响。综述了当前改善镁合金阻尼性能的主要方法,如添加合金元素、控制变形工艺、热处理、控制晶粒尺寸和取向、添加增强相。指出通过添加新的增强相和合金元素,引入位错阻尼之外新的阻尼产生机制,解决阻尼性能与力学性能的矛盾,将是未来高性能阻尼镁合金材料研究的重要方向,而且,产品外形结构设计与阻尼性能的关系也是值得关注的一个新研究方向。

阻尼镁合金的研究现状及发展趋势

阐述了镁合金的阻尼机理及其不足。从合金化、先进的制备技术、镁基复合材料及热处理方面综述了镁合金的研究现状。指出从阻尼机制、组织、制备、热处理四方面综合考虑制备兼顾力学性能的高阻尼镁合金是阻尼镁合金的发展方向。其中,利用先进的制备技术制备多元镁合金是未来阻尼镁合金的一个重要领域。

阻尼镁合金的研究与应用综述

镁具有高的导热导电性、电磁屏蔽性、无磁性和无毒性等特点,是具有高阻尼性能和低密度的工程结构材料。随着航空、航天、建筑、汽车等振动和噪声较为严重的行业对轻质、高强、高阻尼结构材料需求日益增加,阻尼镁合金材料必将成为镁合金研究开发的重要发展方向之一。文章对阻尼镁合金的研究现状和应用进展以及发展趋势进行了综述,重点介绍了Mg-Zr、Mg-Ni、Mg-Cu、Mg-Al、Mg-Zn、Mg-Si、Mg-Li、Mg-RE、镁基复合材料、多孔镁系阻尼镁合金。文章分析指出:镁合金的阻尼机制主要是位错机制,除了刃位错之外,还应加强研究螺位错对阻尼机理的影响;通过添加新的增强相和合金元素从根本上解决阻尼性能和力学性能的矛盾,使设计出的产品外形结构适合减振降噪也是值得关注的一个新方向。

新型镁合金的研究开发与应用

本文详细介始了上海交通大学轻合金精密成形国家工程研究中心开发研制的新型高性能低成本耐热镁合金、阻燃镁合金、高性能阻尼镁合金及高强度高韧性镁合金的显微组织、机械性能、物理化学特性、工艺性能及实际应用效果。此外,还介绍了本研究中心在镁合金成形技术(压铸)、表面处理等方面的开发研究进展。

Damping properties of as-cast Mg-xLi-1Al alloys with different phase composition

Three kinds of different phases of Mg-xLi-1Al alloys with x=5 （full α LA51）, 9 （dual-phase LA91）, and 14 （rich-βLA141） were prepared by vacuum melting method. Their microstructure and damping capacities were investigated by optical microscopy, X-ray diffractometry, and dynamic mechanical analysis. The results show that the addition of Li changes the crystal structure of the alloys and causes new damping mechanisms to emerge. And the appearance of BCC structure makes the damping performance improved remarkably. The lower the elastic modulus is, the smaller the strain is and even the slower the acceleration is. The dual-phase alloy shows a better damping capacity while the temperature changes. Furthermore, all three alloys have two significant peaks：P1 caused by the movement of dislocations on the basal planes and P2 caused by the sliding of grain boundaries.

High damping capacities of Mg-Cu based alloys

The dynamic mechanical analyzer(DMA)was applied to investigate the damping properties of Mg-Cu based alloys.The results show that the as-cast hypoeutectic Mg-Cu binary alloys exhibit ultra-high damping capacities,while the eutectic Mg-Cu alloy exhibits low damping capacity.The strain amplitude dependent damping performance reveals that the dislocation damping mainly dominates in Mg-Cu alloys.Furthermore,the influence of eutectic phase on damping mechanisms of Mg-Cu binary alloys was discussed in detail and the effect of Si addition on the damping of Mg-1%Cu based alloy was also reported.Two damping peaks are observed on the temperature dependent spectrum of Mg-Cu based alloys.One is located at room temperature,which is dislocation related peak;and the other is located at moderate temperature,which is caused by the grain boundary sliding.

Effect of long period stacking ordered phase on damping capacities of as-cast Mg-Zn-Y alloys

The microstructure and damping capacities of MgZnxYi.33x(x=l-4at.%)alloys were discussed and researched.The main phase composition of the alloys consists of a_Mg and long-period stacking ordered(LPSO)phase.Due to increasedLPSO phase,grain size was refined.LPSO phase was advantageous to the damping properties of the Mg-Zn-Y alloys.Mg-7%Zn-12.8%Y has the highest damping capacity up to0.04.Due to stacking fault probability,the LPSO phase in the Mg-Zn-Yalloys could be new damping source to dissipate energy so as to contribute to the improvement of damping capacities.

Effects of Y and Zn on mechanical properties and damping capacity of Mg-Cu-Mn alloy

Optical microscope,X-ray diffractometer,scanning electron microscope,tensile tester and dynamic mechanical analyzer(DMA) were applied to investigate the effects of Y and Zn additions on microstructure,mechanical properties and damping capacity of Mg-3Cu-1Mn(CM31) alloy.The results show that with the increase of Y and Zn contents,the secondary dendrite arm spacing of alloys is reduced;meanwhile,the yield strength is increased.In low strain amplitude,the damping capacity of alloys with Y and Zn addition is lower than that of CM31 alloy.However,in strain amplitude over 5×10-3,the damping capacity of alloy with a trace of Y and Zn addition(1%Y and 2%Zn,mass fraction) increases abnormally with the increase of strain amplitude and is near to that of pure Mg,probably due to the increase of dislocation density caused by the precipitation of secondary phase.The temperature dependence of damping capacity of above alloy was also tested and discussed.

Influence of impurities on damping properties of ZK60 magnesium alloy

The influence of impurities on damping capacities of ZK60 magnesium alloys in the as-cast,as-extruded and T4-treated states was investigated by dynamically mechanical analyzer at room temperature.Granato and Lucke dislocation pinning model was employed to explain damping properties of the alloys.It is found that reducing impurity content can decrease the amount of second-phase particles,increase grain size and improve damping capacity of the as-cast alloy slightly.The as-extruded alloy with lower impurity content is found to possess obviously higher damping capacity in the relatively high strain region than that with higher impurity concentration,which appears to originate mainly from different dislocation characteristics.The variation tendency of damping property with change of impurity content after solution-treatment is also similar to that in the as-extruded and as-cast states. Meanwhile,the purification of the alloy results in an evident improvement in tensile yield strength in the as-extruded state.

Effects of Y on mechanical properties and damping capacity of ZK60 magnesium alloys

The microstructure,mechanical properties and damping capacity of ZK60-xY(x=0,1.5%,2.5%,4.0%,mass fraction) magnesium alloys were investigated by using the optical microscope(OM),X-ray diffractometer(XRD),universal tensile testing machine and dynamic mechanical analyzer(DMA).The mechanisms for damping capacity of referred alloys were discussed by Granato-Lücke theory.The results show that Y additions remarkably reduce grain size(the average grain size is 21.6,13.0,8.6 and 4.0μm,respectively),and the tensile properties are enhanced with grain refining(the yield tensile strength increases to 292 MPa from 210 MPa and ultimate tensile strength increases to 330 MPa from 315 MPa).For the ZK60-xY(x=0,1.5%,4.0%)alloys,the damping capacity decreases with the increase of Y content.However,for the ZK60-xY(x=2.5%)alloy,the damping capacity improves abnormally,which is possibly related to the formation of Mg3Y2Zn3(W)FCC phase in this alloy.