Study Of Damping Performance And Mechanism Of Ultrafine-grained Pure Magnesium

The vigorous development of aerospace industry has brought mankind not only convenience but also noise and vibration problems.Pure magnesium has the best damping performance among metal materials.However,the mechanical properties of pure magnesium are poor and its strength is low at room temperature,which leads to great constraints on its application in industrial fields.Generally,high mechanical properties can be achieved by adding alloy elements and reinforcements.However,it also weakens its intrinsic performance to varying degrees,such as the damping performance and corrosion resistance.Therefore,how to balance the mechanical properties and damping properties has always been the interest of the scientific community.In this paper,the extruded bars of pure magnesium with grain size of 15μm,11μm,560 nm,98nm and 20 nm were prepared by high energy ball milling and hydrogenationdehydrogenation processing.The mechanical properties and damping properties were studied respectively.The results show that the tensile strength and yield strength of the material increase gradually with the decrease of grain size.The yield strength and tensile strength of the sample with grain size of 20 nm reach 224 MPa and 290 MPa,respectively.The damping curves of all samples conform to G-L theory and dislocation damping mechanism.With the decrease of grain size,the damping properties increase first and then decrease.The strain amplitude damping of the sample with grain size of560 nm is the best.It can be seen from the temperature damping spectrum that there is only one internal friction peak for the samples ball-milled for 0 h and 10 h,which is located at 136℃ and 147℃,respectively.In addition,there are two internal friction peaks for the samples ball-milled for 50 h and 100 h.The internal friction peaks of the sample ball-milled for 50 h are located at 130℃ and 283℃ while those of the sample ball-milled for 100 h are located at 113℃ and 267℃.Besides,only the first peak located at 164℃ appears in sample prepared by hydrogenation-dehydrogenation processing.Commonly,the first peak is called P1 peak,which is related to the interaction of dislocations or surface defects such as grain boundaries and point defects.And the second peak is called P2 peak,which is mainly related to grain boundaries.The pure magnesium extruded bar with a grain size of 560 nm can achieve a better balance between mechanical properties and damping properties,and obtain good comprehensive properties.