The hydrogen embrittlement (HE) resistance of a fine-grained equiatomic CoCrFeNi high-entropy alloy (HEA) is investigated via tensile testing under electrochemical H charging. The HE behavior is ...compared with that of HEA specimens charged with 100 MPa of H gas. The fine-grained HEA shows > 40% elongation with a tensile strength of ~800 MPa under electrochemical H charging. Meanwhile, H gas-charged specimens with a uniform distribution of H show deformation twin-related intergranular cracks, whose initiation length decreases owing to grain refinement. Such small cracks, which feature blunted tips, do not significantly affect the fracture of the specimens. The electrochemically H-charged specimens exhibit numerous surface cracks because of their higher surface H content compared with that of the H gas-charged specimens. Nevertheless, similar to the case of the H gas-charged specimens, most of the cracks do not propagate significantly. In conclusion, fine-grained HEA exhibits remarkable resistance to H-related crack growth.
A multi-pass caliber rolling has attracted attentions as an alternative to severe plastic deformation processes. The present study enhanced strength and ductility of AZ31 Mg alloy simultaneously ...through the application of caliber rolling. The improving trends in tensile properties were interpreted with various caliber-rolling strains. The oval/circular-shaped calibers imposed a high plastic strain at the center of cross-section, leading to effective grain refinement to submicron scale. This work also confirmed the texture randomizing effect of caliber rolling. Such microstructural evolutions gave rise to the fabrication of high-strength material. Moreover, the caliber-rolled AZ31 Mg alloys exhibited an improvement in ductility as compared to the as-received sheet-rolled material. This was discussed in terms of activation of non-basal slip systems and suppression of mechanical twinning. This study successfully proved the possibility of caliber rolling to produce a bulk Mg rod with enhanced tensile properties.
•Annealing effect was studied with respect to caliber-rolled AZ31 Mg alloys.•Low-temperature annealing gave rise to trade-off of strength and ductility.•High-temperature annealing led to simultaneous ...deterioration in strength and ductility.•The deterioration is attributed to a grain growth and resultant mechanical twinning.
Recently, multi-pass caliber rolling has been shown to be effective for Mg alloys. This study investigated the effect of subsequent annealing on the mechanical properties of a caliber-rolled AZ31 Mg alloy to modulate the strength-ductility relationship. This annealing gave rise to different trends in mechanical properties depending on the temperature regime. Low-temperature annealing (T ≤ 473 K) exhibited a typical trade-off relationship, where an increase in annealing temperature resulted in increased ductility but decreased strength and hardness. Such a heat treatment did not degrade the high strength-ductility balance of the caliber-rolled alloy, suggesting that the mechanical properties could be tailored for different potential applications. In contrast, high-temperature annealing (T > 473 K) caused a simultaneous deterioration in strength, hardness, and ductility with increasing annealing temperature. These differences are discussed in terms of the varying microstructural features under the different investigated annealing regimes.
The hydrogen embrittlement (HE) resistance of a fine-grained equiatomic CoCrFeNi high-entropy alloy (HEA) is investigated via tensile testing under electrochemical H charging. The HE behavior is ...compared with that of HEA specimens charged with 100 MPa of H gas. The fine-grained HEA shows ˃ 40% elongation with a tensile strength of ~800 MPa under electrochemical H charging. Meanwhile, H gas-charged specimens with a uniform distribution of H show deformation twin-related intergranular cracks, whose initiation length decreases owing to grain refinement. Such small cracks, which feature blunted tips, do not significantly affect the fracture of the specimens. The electrochemically H-charged specimens exhibit numerous surface cracks because of their higher surface H content compared with that of the H gas-charged specimens. Nevertheless, similar to the case of the H gas-charged specimens, most of the cracks do not propagate significantly. In conclusion, fine-grained HEA exhibits remarkable resistance to H-related crack growth.
This study investigated a caliber-rolled Mg–6Zn-0.5Zr (ZK60) alloy as part of an effort to achieve enhanced mechanical properties and bulk dimension out of lab scale. The caliber-rolled ZK60 alloy ...presented a high fraction of dynamically recrystallized (DRXed) grains with submicron sizes. The alloy also exhibited simultaneous improvements in strength and ductility in comparison to commercially extruded ZK60 alloys. The ultrafine-grained (UFG) structure and enhanced mechanical properties were attained while maintaining bulk dimension, which was difficult with severe plastic deformation processes. Furthermore, caliber rolling gave rise to nearly symmetric behavior in terms of yielding. These mechanical improvements in the caliber-rolled ZK60 alloy were interpreted in light of its microstructural characteristics, such as UFG structure, DRX, precipitates, basal texture with tilting of c-axes, and activation of mechanical twinning.
•A caliber-rolled ZK60 alloy was investigated for the first time.•It showed a high frequency of dynamic recrystallization comprising ultrafine grains.•It showed the enhanced strength-ductility balance and yield symmetry.•Effective grain refinement and dynamic recrystallization led to the improvements.•Suppressed activation of extension twinning also contributed to the improvements.
In this study, high strength CuAg foils with nano-lamellar structures were prepared using a pulse electrodeposition method in an environmental-friendly methanesulfonic acid (MSA)-based solution. In ...an MSA-based bath, the Ag+ ion acted as the source for solute atoms and as a brightening agent, which allowed the formation of compact and bright CuAg structures in an additive-free bath. The application of pulse plating led to the formation of a nano-lammellar structure, in which Cu-rich and Ag layers were repeatedly stacked. Because of the contribution of the Ag layer, the as-deposited CuAg foil exhibited a high ultimate tensile strength (927 MPa) even at a low Ag content (2.37 wt%). The strength of the CuAg foil was further improved with annealing at 100–250 °C owing to the stabilization of the phase boundary. Despite a high fraction of the phase boundary, the nanostructure was stably maintained even after annealing at 250 °C for 1 h.
•We fabricated CuAg foils via electrodeposition in a methanesulfonic acid-based bath.•Ag+ ion acts as solute source and brightening agent improving CuAg foil compactness.•The CuAg/Ag nano-lamellar structure is formed via a pulse plating technique.•The Ag layer in the nano-lamellar structure contributes to CuAg strengthening.•The nano-lamellar structure is more thermally stable than nanocrystalline ones.
In this paper, we first propose a scalable transformer network-based reinforcement learning (RL) method for power supply induced jitter (PSIJ) optimization in high bandwidth memory (HBM). The ...proposed method can provide an optimal power distribution network (PDN) decoupling capacitor (decap) design to satisfy the target PSIJ with the minimum number of NMOS decaps. For the given number of decaps, the network is trained to maximize the impedance reduction from 10 MHz to 20 GHz compared to the initial PDN. Also, the network has scalability on the number of decap assignments. Therefore, for given any number of decaps, the scalable network can provide minimized PDN impedance profiles by one inference without re-training. Then, by increasing the decap assignments, the network can find out the minimum number to meet the given target PSIJ. For verification, the proposed network is applied to the HBM2 I/O interface. The network successfully provides the optimized decap designs to satisfy the given target PSIJ values.
In this paper, the coaxial and shielded-twisted pair (STP) cables with intra-pair skew was analyzed by frequency domain analysis method by the equations in close-to-real intra-pair skew setup for ...high definition multimedia interface (HDMI) interface. For the high-speed interface, the intra-pair skew has become critical factor in terms of signal integrity. Heretofore, the intra-pair skew has not been commonly investigated in frequency domain for the high-speed data rate. To verify the intra-pair skew impact on the high-speed interface, the intra-pair skew location was distributed in the coaxial and STP cable assemblies for the real cable setup. Next, the skew impact was verified using frequency domain analysis and the eye-diagram. As the result, by the frequency-domain analysis, the differential loss and the mode conversion of coaxial cable assembly deteriorated due to the intra-pair skew, but STP did not deteriorate. Furthermore, the eye-diagram of the coaxial cable assembly with skew had smaller opening than without any skew, but of STP had little change.
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