Influence Of Strain Rate On The Tensile Deformation Behavior Of GH4169 Alloy

The development of superalloys is closely related to modern aerospace technology, for example, in advanced aircraft engines, superalloy materials are accounted for 40% to 60% of total engine. Due to the importance in defense industry, superalloys become an important symbol of national technology level. GH4169 alloy shows good overall performance range from-253 to 700?. Because of good fatigue resistance, anti-radiation performance, oxidation resistance and corrosion resistance, superalloys are widely used, accounting for 65% the total industrial output of nickel-base superalloys.GH4169 alloy is usually used in dynamic environments, but the existing mechanical properties and deformation behavior parameters of GH4169 alloy are mostly got in static or quasi-static conditions. It has been found that when strain rate exceeds 10s-1, the mechanical properties and deformation behavior change significantly. Therefore it is necessary to study how the strain rate affect deformation behavior of GH4169 alloy, because it has practical significance for design calculations and evaluation of its overall performance.This paper studies the influence of strain rate on tensile deformation behavior of solid solution and aged state GH4169 alloy. After solution processing, got four grain sizes solid solution GH4169 alloy tensile specimens, then study tensile deformation behavior when strain rates are 10-3s-1,101s-1 and 103s-1. Aging Oh, 100h,200h,500h and 1000h to obtain four groups aged GH4169 alloy tensile specimens, then study tensile deformation behavior when strain rates are 10-3s-1,10-2s-1,10-1s-1,101s-, 102s-1 and 103s-1.The results show that when strain rates range from 10-3s-1 to 103s-1, both of yield strength and tensile strength of solid solution GH4169 alloy increase rapidly with the strain rate growing, this phenomenon can be explained by strain rate hardening theory. With strain rate increasing, tensile elongation gets its minimum value when strain rate is 10-1s-1, then has a dramatic rising, this is because the main way of plastic deformation is dislocation gliding under standard static condition, but under dynamic condition, besides dislocation sliding, there are lots of deformation twinnings. Analysis fitting Hall-Petch relationship of solid solution GH4169 alloy, ?0 has accelerating increasing trend with the strain rate increasing, mainly because P-N force increases with strain rate growing significantly, K shows an overall increasing trend, mainly because the critical shear stress of movement of dislocations increases with strain rate growing.With strain rate increasing, both of yield strength and tensile strength of aged GH4169 alloy increase, which can be explained by strain rate hardening theory. Elongation shows clear downward trend, the weekness of larger size precipitates is gradually emerging under high strain rates, deformation coordination ability is more poor, the probability of cracks appearance increases, ductility drops. When the strain rate is low, with the increasing of the average size of precipitates, the way of islocation moves through precipitation phases changes from cut-off mechanism to passing mechanism of aged GH4169 alloy. When the strain rate is high, the deformation behavior changes significantly, dislocations cut through strengthening phase. Fracture fractal dimension of aged GH4169 alloy goes upward with strain rate increasing, shows path of main crack is more complex. This is because under high strain rates, the overall tensile deformation is faster, relatively weakness areas are more difficult to get up with the whole deformation, larger cracks form in many places in a short time, these large cracks connect with each other to cause fracture, the influence of secondary cracks on the movements of main crack is more obvious, leading to the path of main crack is more random.