Study Of The Impact Of Aging On Elastic Hysteresis Error Of Maraging Steel 00Ni18Co8Mo5TiAl

Maraging steel 00Ni18Co8Mo5 TiAl is a kind of high-alloy ultra-high strength steel. It has good formability before aging treatment and is almost no distortion during aging treatment, The one after aging treatment prossess high strength and toughness. Not only have been widely used in bombs, arrows, aerospace, pressure vessels, precision molds, but also used on the strain gauge balance material of the plane to measure aerodynamic loads nowadays. The elastic modulus and elastic hysteresis are the two major factors affecting the measurement accuracy and stabilization of the strain gauge balance. Proper and reasonable aging treatment can improve the elastic modulus and elastic hysteresis of the material. To study the impact of aging on elastic hysteresis error, the paper carried out following studies and obtained appropriate conclusions:According to the research of aging treatment process, the aging process of the maraging steel 00Ni18Co8Mo5 TiAl was confirmed. Aging at 460 ℃, 480 ℃ and 500 ℃, the higher aging temperature, the faster the hardness rising, the shorter time of reaching a peak required, the lower value of the peak hardness. There were Fe2 Mo and Ni3 Ti precipitated under peak aging. Fe2 Mo exerted spherical, of small amount, different sizes and the distribution of Fe2 Mo was ruleless. Ni3 Ti was strip, of small amount and randomly orientation. Martensite matrix had some refinement and lattice distortion. Aging at 480 ℃, high strength, good ductility, and elastic modulus was small and stable. Therefore, it is determined at 480 ℃ for heat preservation 8h was peak-aged condition.Using three parameters,inclued longitudinal wave attenuation coefficient, peak frequency and peak amplitude,the microstructure of materials under different aging states was characterized.The Young’s modulus are measured by ultrasonic method and then compared to the results obtained by tensile method. At 460 ℃, 480 ℃, 500 ℃, before and after the peak aging, because of a large number of Fe2 Mo precipitation in which intragranular(including grain boundaries) of 00Ni18Co8Mo5 TiAl enhanced ultrasound scattering when aging, so that longitudinal wave attenuation coefficient increased continually. The smaller size of the precipitates, the greater the number is and the interference would be more serious. With aging time increasing, peak frequency and peak amplitude of the amplitude spectrum would be significantly increased. Young’s modulus of 00Ni18Co8Mo5 TiAl measured by acoustic under different aging state was close to the values measured by tensile method. It is indicated that the ultrasonic method could be used to measure Young’s modulus of material.The paper researched the relationship between elastic hysteresis error and organizational structure under different aging treatment. Theoretical and experimental proved that elastic hysteresis error varied with load present parabolic relationship. By the hysteresis error of repeated cyclic loading-unload and the fifth cyclic loading-unload, it could be determined that elastic hysteresis error was minimized and relatively stable at 480 ℃ for heat preservation up to 8h. Formation of the hysteresis was mainly due to the micro plastic deformation lead by dislocation glide in internal material tissu when loaded below the yield strength. Precipitates would hinder dislocation glide and affect the stress-strain transferring which resulting hysteresis decreasing.