Cr-Ni-Mn series stainless steel microstructure and properties of metal rubber ma

Metal rubber is a new type of elastic and porous materials which develop from metal materials. The macro-structure of metal rubber is reticular just as high polymer, made up of fine metal wires. When vibrating it dissipates energy so as to act as dampers. At the moment, studies about it is mainly on the absorption of vibration and macro structures, etc. However, no systematic research has been reported on the metal wires used for metal rubber from material aspects and the relation to amortization. As a result, in this dissertation, we studied the microstructure, properties, phase composition and corresponding change after different heat treatments of stainless steel wires. We started from the cold-drawn stainless steel wires used for metal rubber, did a series of experiments, and tried to understand the influence of changes of metal wires on the damp and fatigue properties of metal rubber. By means of microscopy and X-ray diffraction, the microstructure, mechanical properties, martensite transformation and corresponding changes after different heat treatments of cold-drawn stainless steel wires used for metal rubber were studied. The wire diameters were 0.4, 0.3, 0.2, and 0.15mm, respectively. The microstructure of metal rubber produced using these wires were found mainly consisting of martensite induced by cold deformation. The deformation-induced martensite content in the wires increased with the deformation rate, from 81.2% at 36% deformation. SEM observations showed that there were large quantities of voids parallel to the drawing direction, whose volume fractions increased with the deformation. Meanwhile, the tensile strengths of the wires were 1406～2244MPa, the elongations were 13.0%～8.9%. Therefore, we can conclude that the metal rubber produced by such wires should be ultrastrength materials and bear both micro- and macro-voids or porosities. The microstructures almost did not change after 350~500℃ tempering, but the tensile strengths decreased obviously, which were 1050~1804MPa, 1073~1251Mpa and 884~1257MPa after tempered for 30 min at 400℃，450℃ and 500℃, respectively, although at 350℃ the strength decreased only a little. The martensite content increased a little, but the dislocation densities decreased in tempered martensite. The cold-drawn wires recrystallized completely after annealed for 10s at 1050~1100℃ when the elongations of the wires were 18.6%～39.1%, the tensile strengths were973～1210MPa. Experiments show that the elastic modulus of stainless steel wires seems relevant to the dynamic average stiffness and the energy dissipation for friction of metal rubber elements, but the damp dissipation almost unchanged with the temperature. The main fracture way of metal rubber elements is the fractures of wires at stress concentration points. The microstructure of the stainless steel wires changed a little in the middle of the metal rubber samples, but no significant changes were observed in the central and outer parts. The fracture modes of wires were like wood grains, dimples and wheels according to different amplitudes and temperatures.？？