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1、SjScie neeEMEVIER PressAvailable online at Scie nceDirectTransactions of Nonferrous Metals Society of ChinaTrans. Nonferrous Met. Soc. China 22(2012) 1907-1911Low frequency damping capacities of commercial pure magnesiumHU Xiaoshi WANG Xiao-jun1, HE Xiao-dong2, WU Kun1, ZHENG Ming-yi11. School of Ma
2、terials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China;2. Center for Composite Materials and Structures, Harbin Institute of Technology, Harbin 150001, ChinaReceived 10 November 2011; accepted 11 Jane 2012Abstract: The amplitude-dependent and temperaturc-dcpendcnt low
3、frequency damping capacities of magnesium with 99.96% purity were studied by a dynamic mechanical analyzer. The pure magnesium alloys include CPM1 and CPM2 castings having textures of columnar grains which extraordinarily influence the damping behaviours The commercial pure magnesium alloy CPM was r
4、emelted to obtain equiaxed grains, which could remove the effect of texture orientation on the damping behaviours of these pure magnesium alloys. The results of strain amplitudc-dependcnt damping spectrums of these pure magnesium alloys show that the pure magnesium with equiaxed grains possesses the
5、 highest damping capacity. In temperature -dependent damping plot for all these three pure magnesium alloys, (here are two damping peaks and P2 located at 80 and 230 Ct respectively. These two damping peaks arc considered to be caused by the interaction between dislocation and point defects, and the
6、 movement of grain boundaries, respectively.Key words: commercial pure magnesium; crystal orientation; damping capacity; casting texture; aging; crystal defects1 IntroductionMagnesium alloys are very attractive in the applications for aerospace, automotive and other transport industries due to their
7、 low density, high specific strength and high damping capacity. As known, the cast polycrystalline pure magnesium and some magnesium alloys such as Mg-Zr, Mg-Ni and Mg-Si alloys exhibit extraordinary high damping capacity 1.The damping capacity of metallic materials is considered to be connected wit
8、h the presence, movement and interaction of crystal defects, such as dislocations, grain boundaries, secondary phases and impurity atoms 2-4. The amount of these crystal defects and their movability codetermine the damping capacity of a metallic material under certain vibration conditions For Mg all
9、oys, at room temperature, the key damping mechanism is the movement of dislocations, and at higher temperature, there must be some other crystal defects activated to contribute for the damping capacities of the alloys 5-7.The damping capacities of magnesium alloys have been recognized to be dependen
10、t on the maximum strain amplitude and considered to be caused by the movement of dislocations which are pinned by impurity atoms, second phases and nodes of dislocation network on the basal plane 8-11. Normally two different stages of damping in amplitude-dependent damping curves of magnesium alloys
11、 could be clearly observed Therefore, the type, amount and distribution condition of dislocations and point defects in magnesium alloys, and crystal orientations could dramatically influence their damping capacities. For the research of the mechanism of the damping capacities of magnesium alloys, mo
12、re emphasises should be paid to the basic study of very simple structures (such as pure magnesium alloy) with no (or very less) solute and un-solute atoms, second phases, deformation induced crystal defects and so on. In the present study, the damping behaviours of commercial pure magnesium (CPM) al
13、loys CPM1 and CPM2 with purity of 99.96% cut from different directions of the commercial pure magnesium ingot, which has different columnar grain orientations, and the as-cast pure magnesium CPM with equiaxed grains, were studied.Foundation item: Project (50801017) supported by the National Natural
14、Science Foundation of China; project (20080440843) supported by Postdoctoral Science Foundation China; Project (H1T.NSRIF.2009028) supported by the Natural Scientific Research Innovation Foundation of Harbin Institute of Technology. ChinaCorresponding author: HIJ Xiao-shi; Tel: 86-451-86402291; Fax: 4 86-451-86413922; E-mail: huxiaoshi DOI: 10.10161003-6326(1 IXl406-4