Influence Of Twins And Texture On The Internal Friction Peak Of Mg-3Cu-1Mn Alloy

With high-speed and light-mass of the field of aircraft, aerospace and transportindustry, more demands have been proposed for materials to meet the highspeed parts invehicles. It demands that the material not only has excellent mechanical properties, butalso has better damping properties to reduce noise and vibration. Vibration and noiseseriously affect the quality of people’s live, meanwhile the life of the parts are greatlyshorten by them. At the same time, the contradiction between energy shortages andrapid development of the industrial becomes much prominent. Therefore, it is urgentlyto solve the problem of world-wide vibration, noise hazard, the energy shortage and soon. It is one of the most effective measures to prevent vibration, noise, reducing energyconsumption from the perspective of material, so the magnesium alloy with highdamping, low-density, high-specific strength has been focused on.However, the mechanical properties of the as-cast magnesium alloys can not meetthe needs of industrial development. When the plastic deformations are used tosignificantly improve the mechanical properties of magnesium alloy, the dampingproperties will be decreased. The twinning and texture organization are easy to form inmagnesium alloy with hexagonal close-packed (HCP) structure when it is in the processof plastic deformation. The influence of these organizations on the damping propertiesof the magnesium alloys has not been study clearly. Therefore, at present, researchingthe regulation of twinning and texture on the damping properties of magnesium alloybecomes a problem to be solved urgently for the material with high strength and highdamping integration function. It is noteworthy that the the mechanism of the damping inMg-3Cu-1Mn alloy contained a large number of twins did not fully comply with theG-L theory in some relevant research. Whether is worked of twins causing a lot ofattention of scholars.To solve the above problem, Firstly, the amount and distribution of tensiletwinning in Mg-3Cu-1Mn alloy were controlled by designing a once rolling at roomtemperature with small deformation in this paper. And it also Combined with heattreatment means to "purify" the dislocation to reduce its impact, and then analyze theeffect of tensile twinning on the temperature damping spectrum and damping propertiesat room temperature in the Mg-3Cu-1Mn alloy. The results show that the unstabletemperature damping peak P3become very inconspicuous with the twins disappearrapidly in the second temperature-damping spectrum, which doesn’t appear in the temperature-damping spectrum of Mg-3Cu-1Mn alloy as-Undeformed. In addition, thedamping properties of the as-rolled Mg-3Cu-1Mn alloy at room temperature gets asubstantial recovery with the disappearance of the tensile twins, which approaches thedamping properties of the alloy with on deformation. This phenomenon indicates thatthe tensile twins have bad affect on the strain-damping properties of Mg-3Cu-1Mnalloy.Secondly, the effect of deformation texture on the damping capacity of Mg-3Cu-1Mn alloy was analyzed in this paper. The Mg-3Cu-1Mn alloy was processed bysmall deformation of hot-rolled and different extrusion ratio, and then the dislocationand twins was purified thought heat treatment means. The typical basal panel textureand basal fiber texture formed in the alloys after those treatments. The results show that:(a) the amplitude-dependence of internal friction reduced with the basal panel textureenhanced.(b) the amplitude-dependence of internal friction increase as the angleexpanding with extrusion axis. It is suggested that: the amplitude-dependence ofinternal friction increase as the angle between the extrusion axis and the length directionof the damping samples get greater.Finally, in order to completely rule out the influence of dislocation density,twinning and grain boundary after plastic deformation, this experiment casts puremagnesium ingots with large columnar crystals and Mg-3Cu-1Mn alloy ingots withpreferred orientation grains by directional solidification technique. And then observe theC-axis direction of the single crystal and preferred orientation with XRD Single crystaltest and texture test to analysis the relationship between damping properties and grainorientation. The results show that: with the increase of angle between grain C-axis andthe sample length direction, consistent with the results of the preceding, theamplitude-dependence of internal friction of Mg-3Cu-1Mn alloy and pure magnesiumbecome smaller; The grains prefer to growth in the magnesium alloy by directionalsolidification, and the preferential direction deflects with the addition of alloyingelements; The damping property of pure magnesium casted by directional solidificationis significantly better than ordinary casting pure magnesium; The Mg-3Cu-1Mn alloyprepared by directional solidification technique also has excellent high-strain dampingproperties, which is not only more than10times better of ordinary castingMg-3Cu-1Mn alloys, but also much higher than ordinary casting pure magnesium athigh strain range..