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Microstructure and Cracking Noise in High Entropy Alloys
Published in T.S. Srivatsan, Manoj Gupta, High Entropy Alloys, 2020
In 2013, Choudhary et al. [24] studied the serrated flow of 9Cr-1Mo steel and summarized the effects of temperature and strain rate on it. They believe that it is the repetitive and systematic fluctuation of the load on the stress-strain curve during plastic deformation. Different physical processes can cause different changes in the serrated flow characteristics. It is divided into seven categories: (1) sudden and instantaneous increase of movable dislocation density or velocity; (2) interaction of dislocation movement and solute atom diffusion; (3) order–disorder transition caused by dislocation movement; (4) continuous twinning deformation; (5) phase transition caused by stress; 6) local temperature rise resulting from adiabatic shear; (7) the yielding phenomenon of the fracture surface of the brittle material under specific stress state. The most widely recognized is the dynamic strain aging effect (DSA effect), that is, the dynamic interaction in the plastic deformation of the aggregation of solute atoms near dislocations, and the dislocation.
Microstructural Characteristics of Metals
Published in Vladimir B. Ginzburg, Metallurgical Design of Flat Rolled Steels, 2020
Caused by strain aging, this phenomenon leads to appearance of so called Lüder strain lines after subsequent deformation. Strain aging can occur during the tension test that is conducted within the temperature range from 150 °C to 350 °C (from 302 °F to 662 °F). This phenomenon is known as dynamic strain aging, or blue brittleness. Strain aging is commonly minimized by removal of nitrogen N. This is frequently accomplished, for instance, by adding aluminum A1 to the steel, so about 0.05% of aluminum is retained in the product, forming aluminum nitride (AIN).
Strengthening mechanisms
Published in Gregory N. Haidemenopoulos, Physical Metallurgy, 2018
In certain cases strain aging takes place during plastic deformation at relatively high temperatures. This phenomenon has been termed dynamic strain aging or Portevin Le Chatelier effect (PLC) and is associated with discontinuous plastic flow (Figure 8.11). The appearance of yield points is not limited to steels or other alloys containing interstitial solutes forming Cottrell atmospheres but it appears to other materials as well, such as Ge and LiF.
Constitutive modeling of dynamic strain aging in commercially pure bcc metals
Published in Mechanics of Advanced Materials and Structures, 2023
As stated earlier, dynamic strain aging occurs due to the interaction of impurity/solute atoms with the dislocations. These dislocations are pinned by the diffusion of solute atoms resulting in an increase in the waiting time required for their movement. When this waiting time becomes equal to the relaxation time needed for the solute atoms to diffuse over the average width of the obstacles, DSA is activated [2]. Now for further movement of dislocations, a higher stress is required and hence we observe an increase in the metal’s strength. Contemplating above, a simple demonstration of a metallic structure containing impurity and solvent atoms is shown in Figure 1. The solvent atoms are bonded to each other while the impurity atoms such as C, N and O are distributed in the structure in small quantities within the available interstitial sites. Since the metals have a closed pack structure, these are the only available sites for these impurity atoms. These atoms are stressed due to limited available space and will always move toward a larger site to lower their energy whenever possible.
Electroplasticity: A review of mechanisms in electro-mechanical coupling of ductile metals
Published in Mechanics of Advanced Materials and Structures, 2022
Nikolay K. Dimitrov, Yucheng Liu, M. F. Horstemeyer
In the EP literature, the concept of “Dynamic Strain Aging” (DSA) was introduced by Sprecher et al. [16] to explain irregularities in the EP behavior of FCC Nickel and HCP Titanium since DSA is a process where aging is sufficiently rapid to occur during straining and produce a variety of inhomogeneous deformations. Two recent works feature this concept but in a different connotation. Lee et al. [45] employed the DSA (not EP) to cover the gap between experimental results and thermal expansion/softening calculations. They concluded the DSA contribution was yet to be associated with the EP effect [45]. On the other hand, Wang et al. [46] treated the DSA separately from the EP effect with the latter considered insignificant. In their work, the calculated thermal expansion stress exceeded the experimentally obtained stress drop from the passing of a single electric pulse for the first time since the discovery of the EP phenomenon. Wang et al.’s [46] used the DSA terminology to explain their results in a manner, exactly opposite to the one employed in [45]. Clearly, future work is required to sort out the controversies in the DSA/EP relationship.
Influence of processing temperature on formability of thin-rolled DP590 steel sheet
Published in Materials and Manufacturing Processes, 2020
Sandeep Pandre, Ayush Morchhale, Nitin Kotkunde, Swadesh Kumar Singh
Ma et al.[17] performed the Nakazima test based on the ASTM E2218-15 standard for plotting FLD. They performed experiments for DP590 steel at room temperature (RT) and concluded that different types of fractures occurred in the two regions of FLD. Shear-induced fracture occurred in the T–C region with a sample of 10 mm width while dimple-dominant fracture occurred in the T–T region with a sample of 180 mm width. Sahu et al.[24] also performed Nakazima test on DP590 and found major strain to be varying between 2.5% and 8% and the minor strain to be varying between −1.25% and 5%. They further concluded that the applied pressure over die in the form of blank holding pressure (BHP) and the lubricant plays a very crucial role in deciding the limiting strains and preventing the occurrence of wrinkles on the finally formed product. Simsir et al.[25] plotted the FLD of DP590 steel for the temperature range of RT to 400°C. They found that there is significant decrement in the formability and the ductility of material within the temperature range of 200–300°C and concluded that it is because of the dynamic strain aging (DSA) effect. Pandre et al.[5] also reported DSA effect for DP590 within the same temperature range.