Papers by Keyword: Dynamic Strain Aging

Abstract: In the present work, uniaxial tension tests have been conducted to study the mechanical response of a commercial Al4.5wt%Mg alloy (AA5182). The measurements range from the strain rate of 10^-4 to 10⁰ s^-1 at room temperature. Digital image correlation (DIC) is also utilized to characterize the heterogeneous deformation of PLC localization. An extremely high camera frame rate (1000Hz) is applied to accurately measure the critical strain of instabilities, especially for tests at high strain rates (>10^-1 s^-1). The objective of this work has been to evaluate currently existing constitutive and physically based models to see to which extent they can match the experimental findings related to dynamic strain aging, i.e. stress-strain curves, work hardening behavior and critical strain behavior.

Abstract: The uniaxial tensile tests were conducted at different temperatures to explore the coupled influence of stacking fault energy (SFE) and short-range clustering (SRC) on the plastic deformation behavior of Cu-Ni alloys. The results demonstrate that the ultimate tensile strength and uniform elongation decrease with increasing temperature due to the competitive influence of SFE and SRC. Dynamic strain aging (DSA) effect is observed at 200 and 250°C, and such an effect becomes more notable with increasing Ni content. The occurrence of DSA effect is thought to be caused by pinning of moving dislocations by SRC and diffusing solute atoms. The plastic deformation mechanisms for Cu-Ni alloys is mainly governed by wavy slip of dislocations at different temperatures, since the SFE of Cu-Ni alloys are very high especially at high temperatures, and the effect of SRC can be nearly ignored.

Abstract: The manifestation of dynamic strain aging (DSA) in Inconel 718 is reported in this work. Analysis were performed in the material with different microstructures resulting from solution anneal and aging treatment. Tensile tests were made under secondary vacuum with temperature ranging between 200 and 950°C and strain rates of 3.2 x 10^-3 to 3.2 x 10^-5 s^-1. Results showed the range of DSA occurrence. Analysis indicates that at lower temperatures, from approximately 200 to 450°C, serrations are controlled by the diffusion of carbon. At higher temperatures, until 800°C, DSA coincided with the occurrence of other thermally activated phenomena: dynamic precipitation, especially γ’’, and Oxidation Assisted Intergranular Cracking (OAIC). It was observed that competitive phenomena affect DSA manifestation directly due to the availability of niobium in solid solution.

Abstract: The paper considers the features of the manifestation of dynamic strain aging (DSA) effect during severe plastic deformation processing via equal-channel angular pressing of low-carbon steel 10 and during the deformation processing via rolling of steel 20Kh. The deformation mechanisms under different regimes of deformation processing are analyzed. The temperature ranges for the manifestation of the DSA effect during the deformation by rolling of steel 20Kh and by equal-channel angular pressing of steel 10 are established. It is demonstrated that the deformation of low-carbon steels in the temperature range of DSA leads to further structure refinement and, as a consequence, to the enhancement in strength properties.

Abstract: The influence of excess Mg on the Mode I propagation of fatigue crack was examined in newly developed precipitation-hardened Al alloy containing Zr and excess Mg. The aim of this study was to evaluate the underlying factor affecting fatigue crack growth rate in the stage II region. For this purpose, the rotating bending fatigue tests were performed in constant amplitude loading, and replication technique with an optical microscope was used to measure the crack growth in the Al alloys. Through analyses of the crack propagation on the specimen surface and striation formation of the fracture surface, the effects of excess Mg in the Al alloys were clarified to promote the occurrence of mode I fatigue crack, and decelerate the fatigue crack propagation. These facts suggest that the dynamic strain aging of Mg induces the formation of fatigue striation and reduce the driving force of the crack propagation. The findings were supported by the fractographic observations in the fatigue crack propagation region.

Abstract: Ratcheting is the progressive directional accumulation of deformation due to asymmetric loading in structures. Coffin-Manson plots derived from ratcheting experiments conducted at temperatures over the range, 823-923 K showed anomalous behavior at 873 K and 923 K in the form of dual slope and positive slope respectively, which was attributed to a change in the deformation mechanism during ratcheting in the above temperature domain. This was also reflected in the transition in the fracture mode from fatigue to creep at 873 and 923 K.