Papers by Keyword: Planar Slip

Abstract: To explore the role of dislocation slip mode playing in the size effect of mechanical behavior of metallic materials, the tensile behavior of Cu-5at.%Mn and Cu-20at.%Mn alloys with thickness (t) spanning from 0.1 to 2.0 mm is investigated. The results reveal that the yield strength σ_YS of Cu-5at.%Mn alloy displays an independence of thickness, whereas the ultimate tensile strength σ_UTS and the uniform elongation δ show an obvious size effect. The σ_UTS and δ first slightly decrease as t is reduced from 2.0 to 0.5 mm, but evidently drop when t is below 0.5 mm. A similar size effect is also exhibited in Cu-20at.%Mn alloy; however, the variation trend of “the smaller the weaker” in size effect can be weakened by the planar slip of dislocations occurring during the deformation of this alloy.

Abstract: nconel 718 is an age hardenable nickel base supper alloy with high strength at elevated temperatures, and excellent creep properties. It is used extensively in turbine discs, blades where components experience elevated temperatures for prolonged duration, leading to coarsening of the microstructure. To evaluate the life of such components after prolonged exposure to service conditions, LCF properties at such large grain sizes are essential. For this purpose, low cycle fatigue (LCF) behavior of forged Inconel 718 turbine rotor disc having large grain size was studied at room temperature. Total strain controlled fatigue tests were conducted in air at ambient temperature on this alloy in solution treated and aged condition. The results indicated that the material exhibits cyclic strain softening and the cyclic yield strength is lower by 40% compared to the monotonic yield strength. The deformation takes place by multiple planar slip.

Abstract: Tensile deformation behavior of the high-nitrogen austenitic Fe-18Cr-14Mn-4Ni-3MoxN steel with various nitrogen contents has been studied. The nitrogen content of the steel varied from 0.28 to 0.88 wt. %. Nitrogen atoms in high nitrogen steel (HNS) make an interstitial solid solution by being scattered in the steel constituting a short-range order. They strengthen the austenite matrix without deteriorating ductility of the steel. The present investigation was carried out to elucidate the hardening and plasticizing role of the nitrogen in the HNS by analyzing tensile deformation behavior of the steel containing various nitrogen contents. Tensile tests of the steel specimens were performed at room temperature with a constant strain rate of 5x10-5/sec. Microstructure of the tested specimens was analyzed to explore the deformation mechanism of the HNS as a function of nitrogen contents. The flow stress of the steel increased with the increase of the nitrogen content; however, the specimen with the highest nitrogen content (0.88 wt. %) showed saturated strength and reduced ductility. The superior mechanical property of the HNS was explained by the low stacking fault energy and the twin-induced plasticity provoked by the nitrogen.

Abstract: Both tensile and strain controlled low cycle fatigue (LCF) tests were conducted for 316L and 316LN at 550oC and 600oC to investigate the nitrogen effect on the deformation behavior of type 316L stainless. The waveform of LCF was a symmetrical triangle with a constant strain rate of 4×10-3/s was employed for most tests. It shows that the addition of nitrogen in the alloy results in an increase in tensile strength but a decrease in ductility. Both the alloys exhibited cell structure after severe tensile deformation. However, after low cycle fatigue, only planar slip band is observed in 316LN, whereas cell structure is still the main feather of microstructure in 316L. This is due to the strong interstitial-substitutional Mo-N pairs and various stress strain conditions.