Alloy Design Research Articles

Enhancing the plasticity of HfZrTiCr x alloys by forming single phase solid solutions via reducing Cr content

ABSTRACT The solid solution design strategy bolsters the comprehensive mechanical properties of high/medium entropy alloys (H/MEAs), yet its utilisation within hexagonal close-packed (HCP) H/MEAs remains notably limited. Here, exploring the impact of reduced Cr content (x = 0.3, 0.1, and 0) from the HfZrTiCr0.5 prototype alloy, our study successfully obtained a novel HCP single phase MEA and investigated the relationship between microstructure and mechanical properties. Decreasing Cr content led to the diminishing presence of the Laves phase, culminating in a single HCP phase solid solution at x = 0.1. The Laves phase, arising from negative enthalpy between Cr and other elements and lower atomic radius of Cr, acted as crack initiation sites, resulting in brittle fracture (x = 0.5) alloy and limited plasticity strain of 3.5% (x = 0.3). Conversely, the HfZrTiCr0.1 alloy exhibited impressive combined yield strength (1360 MPa) and plasticity strain (14.5%), attributed to prominent solid solution strengthening and enhanced dislocation movement within the solid solution structure. These findings offer insights into manipulating Cr content to form HCP solid solution structures, potentially broadening solid solution alloy design strategies for superior mechanical properties in HCP H/MEAs.

Exploring microstructure variations and hydrogen storage characteristics in TiVNbCrNi high-entropy alloys with different Ni incorporation

In recent years, high-entropy alloys (HEAs), as a novel class of hydrogen storage materials, have been deemed highly promising due to their extensive compositional tunability and the unique high entropy effects. This study aims to enhance the comprehensive hydrogen storage performance of the TiVNbCr-based HEA by introducing Ni. The effects of Ni addition on the microstructural evolution of the alloy and its impact on activation properties, hydrogen absorption and desorption kinetics, thermodynamics, and cycling performance under the complex physicochemical environment of multiple principal elements was systematically investigated. The findings indicate that Ni addition shortens the activation incubation period of the alloy but more Ni reduces the intrinsic hydrogen absorption kinetics. In the Ti25V30Nb10Cr33Ni2 alloy, a high reversible hydrogen storage capacity of up to 2.2 wt% at room temperature was achieved, surpassing most of the currently reported body-centered cubic (BCC)-structured high-entropy hydrogen storage alloys. Furthermore, the influence of Ni on the alloy's hydrogen desorption kinetics and cycling hydrogenation performance was studied. Results from 110 cycles of testing reveal that the introduction of Ni-induced Laves phases can act to relax stress, thereby reducing strain accumulation during the hydrogen absorption and desorption cycling process. This could provide guidance for the design of high-entropy hydrogen storage alloys with extended cycling lifetimes.

Thermal activation and dislocation dynamics in Ti–6Al–4V alloy

The tensile stress relaxation behaviour is experimentally investigated for Ti–6Al–4V alloy across a temperature range of −60, −30, 20, 120, and 230 °C. Interestingly, the results revealed that the alloy exhibited the lowest resistance to stress relaxation at 20 °C, i.e., room temperature. This resistance was found to increase with both increasing and decreasing test temperatures. The apparent activation volume values, which indicate the dislocation mean free path, increase with strain due to a decrease in activable dislocation segments. Furthermore, these values were found to be proportional to the test temperature, resulting from higher dislocation mobility at moderate temperatures (230 °C and 120 °C) than at lower temperatures. Our experimental and analysis results indicate that dislocation-mediated plastic deformation predominates in all tested temperature conditions. However, the transition from planar to wavy dislocation configuration, observed through Transmission Electron Microscopy (TEM) between temperatures of −30 and 20 °C, along with the change in activation volume, suggests a critical temperature at which dislocation mechanism changes in the Ti–6Al–4V alloy. A rapid exhaustion of a substantial amount of mobile dislocation density, which significantly contributes to time-dependent deformation was observed at 230 °C. These findings provide valuable insights into the mechanisms underlying the stress relaxation behaviour of Ti–6Al–4V alloy at different operational temperatures, offering practical implications for improved alloy design and manufacturing processes.

Understanding grain boundary segregation and solute drag using computational and machine learning studies

Grain boundary (GB) solute segregation has been used as a strategy to tailor the properties and processing pathways of a wide range of metallic alloys. GB solute drag results when segregated alloying elements exert a resistive force on migrating GBs hindering their motion. While GB segregation has been the subject of active research, a detailed understanding of solute drag and the migration kinetics of doped boundaries is still lacking, especially in technologically-relevant alloys. Through theoretical analysis, mesoscale modeling, and machine learning studies, we investigate GB segregation and solute drag and establish design maps relating drag effects to relevant alloy and GB properties, i.e., the complete alloy design space. We find that solute drag is dominant in immiscible alloys with far-from-dilute compositions in agreement with experimental observations of GB segregation in metallic alloys. Our analysis reveals that solute–solute interactions within the GB and the degree of segregation asymmetry greatly influence solute drag values. In broad terms, our work provides future avenues to employ GB segregation to control boundary dynamics during materials processing or under service conditions.

Research on Alloy Design and Process Optimization of Al–Mg–Zn-Cu-Based Aluminum Alloy Sheets for Automobiles with Secured Formability and Bake-Hardenability

In this study, the compositional design of high-formability, high-bake-hardening Al–Mg–Zn-Cu-based aluminum alloys was carried out, and process conditions were established to secure mechanical properties under harsh conditions for Al–Mg–Zn-Cu-based alloys. Using JMatPro13.0 for precipitation phase simulation, the optimal pre-aging temperature and time of the design composition were selected. Through the introduction of pre-aging, it was confirmed that no over-aging phenomena occurred, even after bake-hardening, and it was confirmed that it could have mechanical properties similar to those of test specimens subjected to traditional heat treatment. Through DSC (Differential Scanning Calorimetry) and TEM (Transmission Electron Microscope) analyses, it was found that pre-aging provided sufficient thermal stability to the GP (Guinier–Preston) zone and facilitated transformation to the η’-phase. In addition, it was confirmed that, even under bake-hardening conditions, coarsening of the precipitation phase was prevented and number density was increased, thereby contributing to improvements in the mechanical properties. The designed alloy plate was evaluated as having excellent anisotropy properties through n-value and r¯-value calculations, and it was confirmed that a similar level of formability was secured through FLC (Forming Limit Curve) comparison with commercial plates.

Substitution potential of La/Ce/Er for high-cost Sc in rare-earth Al alloys: A comprehensive first-principles study

Al–Sc alloys have high strength, plasticity, and corrosion resistance, making them ideal lightweight materials for the aerospace and automotive industries. However, the practical application of these alloys is constrained by the high cost of Sc. We investigate the substitution potential of lower-cost rare-earth elements X (X = La, Ce and Er) for the expensive Sc in Al–Sc alloys through first-principles calculations. Assessing substitution formation energy, substitutional segregation, and their impact on (001), (110), and (111) γ-Al/γ′-Al3Sc interfaces, results highlight Er as the most promising candidate among the three, thermodynamically replacing Sc in Al3Sc precipitates. Er atoms selectively segregate to γ-Al/γ′-Al3Sc interfaces, enhancing stability by reducing interface energies. The morphology of precipitates undergoes a transition from a truncated cuboctahedron to an {111}-faceted octahedron. Increased Er segregation further bolsters interfacial fracture strength, attributed to segregation-induced charge accumulation. Our work could offer reference for the design of rare-earth Al alloys with low-cost and high-performance.

Unveiling the Mo effect on the microstructural stability of L12-strengthened chemically complex alloys

The influence of Mo on the coarsening behavior of L12-precipitates in chemically complex alloys (CCAs) was thoroughly investigated. Mo addition significantly impacted the morphology, misfit, and microstructural stability of L12-precipitates during aging treatment. Mo incorporation into the B sublattice sites of L12-precipitates (along with Al and Ti) increased their volume fraction and solvus temperature. It also weakened the segregation of solutes between the FCC-matrix and L12-precipitates, resulting in reduced misfit. However, during the aging processing, the misfits in all three CCAs continuously increased. Quantitative analysis revealed that a misfit of approximately 0.5 % yielded cubic morphology of L12-precipitate for CCAs with positive misfits. Further coarsening kinetics studies unveiled a transition from initial matrix-diffusion controlled coarsening to interface-reaction controlled coarsening. Notably, Mo addition prolonged the matrix-diffusion controlled stage and delayed the transition to interface-reaction controlled coarsening. These findings provide valuable insights that can guide future alloy design and heat treatment strategies to optimize the high-temperature structural performance of L12-precipitate CCAs.

Alloying effects on the transport properties of refractory high-entropy alloys

Additive Manufacturing (AM) has opened new frontiers for the design of refractory high-entropy alloys (HEAs) for high-temperature applications. The thermal conductivity of the AM feedstock is among the most important thermo-physical properties that control the melting and solidification process. Despite its significance, there remains a notable gap in both computational and experimental research concerning the thermal conductivity of HEAs. Here, we use density functional theory (DFT) to systematically investigate the alloying effects on the transport properties of Ti-Cr-Mo-W-V-Nb-Ta RHEAs, including electrical and thermal conductivities and Seebeck coefficient. The relaxation time of charge carriers is a key underlying parameter determining thermal conductivity that is exceedingly challenging to predict from first principles alone, and we thus follow the approach by Mukherjee, Satsangi, and Singh [Chem Mater 32, 6507 (2022)] to optimize the relaxation time for RHEAs. We validated thermal conductivity predictions on elemental solids, binary and ternary alloys, and RHEAs and compared them against thermodynamic (CALPHAD) predictions and our experiments with good correlations. To understand observed trends in thermal conductivity, we assessed the phase stability, electronic structure, phonon, and intrinsic- and tensile strength of down-selected RHEAs. Our electronic structure and phonon results connect well with the observed compositional trends for thermal transport in RHEAs. Our DFT assessment and CALPHAD predictions provide a unique design guide for RHEAs with tailored thermal conductivity, a critical consideration for AM and thermal-management applications.

Design of hydrogen embrittlement resistant 7xxx-T6 aluminum alloys based on wire arc additive manufacturing: Changing nanochemistry of strengthening precipitates

In this work, atom probe tomography technique is used to investigate how wire arc additive manufacturing (WAAM) changes the nanochemistry of nanoprecipitates and grain boundaries after peak aging of a high strength Al-Zn-Mg-Cu alloy. The effect of the change in nanochemistry of nanoprecipitates on the hydrogen embrittlement of the additively manufactured aluminum alloy is investigated using a three-point bending test in humid air. The results show that the unique in-process heat treatment during WAAM, offers the possibility to modify the nanochemistry of nanoprecipitates and improve the resistance to hydrogen embrittlement of the Al-Zn-Mg-Cu alloys in the peak aged state without sacrificing mechanical performance. Density functional theory shows that the WAAM process transforms the interfaces between matrix and precipitate into a strong hydrogen trap, which can reduce the hydrogen content of grain boundaries and suppress hydrogen-induced intergranular fracture.

A novel Fe-Mn-Al-Ni-Ta-B superelastic polycrystalline alloy with high stability and low thermal hysteresis

The demand for advanced shape memory alloys, with good processability, high stability, and excellent superelasticity, is highly desirable in widespread practical applications. Here, we demonstrated a novel Fe-34Mn-12.5Al-7.5Ni-2.5Ta-0.05B (at%) polycrystalline alloy (FMAN-Ta-B) with good strain-recovery pseudoelastic behavior (5.68% at a compressive strain of 8%), ultra-low thermal hysteresis (∼81 K), and relatively high stability. In this alloy, highly ordered D03-structured precipitates (Ta-riched Fe3Al) (∼26.3 nm) coupled with B2 precipitates (NiAl) (∼19.6 nm), and dispersive distributed in the A2 (austenitic) matrix. On the one hand, D03-structured precipitates act as a connecting structure between B2 precipitates and the matrix, exhibiting low mismatch with the matrix and inducing a thermoelastic martensitic transformation and good strain recovery in the alloy. On the other hand, D03 nanoprecipitates with high structural and thermal stability limited the growth of B2 precipitates and reduced the size-dependence of the superelasticity for the B2 precipitate, thus elevating the aging temperature and enhancing the thermostability of superelasticity. The drastically improved superelasticity and low thermal hysteresis provide useful insights into the design of high-performance ferrous superelastic alloys.

Fluctuations in misfit volume by interstitial carbon atoms contribute to the unusual dislocation loop evolution in high-entropy alloys under irradiation

Dislocation loops play a pivotal role for the irradiation behavior and associated mechanical properties of materials. This study employs advanced transmission electron microscopy, nanoindentation and first-principles calculations to elucidate the impact of interstitial carbon atoms on the evolution of dislocation loops in an Fe49.5Mn30Co10Cr10C0.5 high-entropy alloy under ion irradiation at temperatures ranging from 420 °C to 540 °C with a peak dose of 50 DPA. Interstitial carbon atoms have been revealed to broaden the size distribution of dislocation loops, rendering their morphologies more jagged, and consequently inducing a more substantial pinning effect. These outcomes can be attributed to the enhancement of misfit volume fluctuations of the alloying elements, which drives more severe local lattice distortions and larger variation of local chemical environments. As a result, these fluctuations promote the local pinning of dislocation loops, lead to their rugged movement and contribute to the rise in hardening. Our findings bring previously unrecognized insights into the role of interstitial carbon atoms in influencing the nature of dislocation loops in high-entropy alloys, and provide important clues to the design of alloys for nuclear applications.

Tailoring the deformation mechanisms in a Ni-Co-based superalloy by controlling γ′ precipitate size

The role of micro-twins in the high-temperature deformation of superalloys is crucial and influenced by precipitates and deformation conditions. This study investigates the deformation mechanisms in a Ni-Co-based superalloy with γ′ precipitates varying from 31 to 122 nm under two compression conditions at 760 °C. The deformation mechanism exhibits a close correlation with the size of γ′ precipitates under 5 % stain, while the formation of micro-twins is relatively limited. Microtwinning becomes the predominant deformation mode when compressed to 20 %. The micro-twins reach the peak intensity for the alloy with 47 nm-sized γ′ precipitate. The optimizing of γ′ precipitate size can significantly enhance the formation of micro-twins in Ni-Co-based superalloys. This strategy of modulating the deformation mechanism through precipitate size regulation offers valuable insights for the design of advanced alloys.

Tensile Properties of a Non-Equiatomic Ni–Co–V Medium Entropy Alloy at Cryogenic Temperature

The development of strong and ductile alloys for application in cryogenic temperatures has long been sought after. In this work, we have developed a face-centered cubic Ni10Co56.5V33.5 multi-principal element alloy (MPEA) that exhibits a balanced combination of high strength and good ductility at 77 K, based on the considerations of large local lattice distortion (LLD) and low stacking fault energy. The small-grained Ni10Co56.5V33.5 MPEA exhibits a yield strength of 1400 MPa and an ultimate tensile strength of 1890 MPa, while preserving a good ductility of 23%. Moreover, precession electron diffraction and transmission electron microscopy revealed multiple deformation mechanisms, including wavy dislocations, atypically severely twisted dislocation bands, hierarchical stacking faults, and deformation twins, which are implicated in the alloy’s outstanding mechanical performance. These insights offer a strategic guide for the design of strong and ductile alloys, particularly for utilization in extreme environments.

Revealing the exceptional cryogenic strength-ductility synergy of a solid solution 6063 alloy by in-situ EBSD experiments

A solid solution 6063 aluminium alloy features an exceptional combination of strength and ductility at 77 K. Here, the deformation mechanisms responsible for superior strength-ductility synergy and excellent strain hardening capacity at a cryogenic temperature of the alloy were comparatively investigated by in-situ electron backscatter diffraction (EBSD) observations coupled with transmission electron microscopy (TEM) characterization and fracture morphologies at both 298 and 77 K. It is found that kernel average misorientation (KAM) mappings and quantified KAM in degree suggest a higher proportion of geometrically necessary dislocations (GNDs) at 77 K. The existence of orientation scatter partitions at 77 K implies the activation of multiple slip systems, which is consistent with the results of potential slip systems calculated by Taylor axes. Furthermore, dislocation tangles characterized by brief and curved dislocation cells and abundant small dimples have been observed at 77 K. This temperature-mediated activation of dislocations facilitates the increased dislocations, thus enhancing the strain hardening capacity and ductility of the alloy. This research enriches cryogenic deformation theory and provides valuable insights into the design of high-performance aluminium alloys that are suitable for cryogenic applications.

Compositional design of multicomponent alloys using reinforcement learning

The design of alloys has typically involved adaptive experimental synthesis and characterization guided by machine learning models fitted to available data. A bottleneck for sequential design, be it for self-driven or manual synthesis, by Bayesian Global Optimization (BGO) for example, is that the search space becomes intractable as the number of alloy elements and its compositions exceed a threshold. Here we investigate how reinforcement learning (RL) performs in the compositional design of alloys within a closed loop with manual synthesis and characterization. We demonstrate this strategy by designing a phase change multicomponent alloy (Ti27.2Ni47Hf13.8Zr12) with the highest transformation enthalpy (ΔH) -37.1 J/g (-39.0 J/g with further calibration) within the TiNi-based family of alloys from a space of over 2 × 108 candidates, although the initial training is only on a compact dataset of 112 alloys. We show how the training efficiency is increased by employing acquisition functions containing uncertainties, such as expected improvement (EI), as the reward itself. Existing alloy data is often limited, however, if the agent is pretrained on experimental results prior to the training process, it can access regions of higher reward values more frequently. In addition, the experimental feedback enables the agent to gradually explore new regions with higher rewards, compositionally different from the initial dataset. Our approach directly applies to processing conditions where the actions would be performed in a given order. We also compare RL performance to BGO and the genetic algorithm on several test functions to gain insight on their relative strengths in materials design.

Advancements in machine learning for predicting phases in high-entropy alloys: a comprehensive review

High entropy alloys (HEAs) are distinguished by their enhanced physicochemical properties, attributed to the formation of various phases such as solid solution (SS), intermetallic (IM), or a combination (SS + IM). These phases contribute distinctively to the microstructure of the alloys. A critical aspect of alloy design revolves around accurately predicting these phases, which has led to the integration of sophisticated data vetting methods and Machine Learning (ML) algorithms in recent research. This review paper aims to provide a comprehensive analysis of the advancements in phase prediction accuracy within HEAs, an essential component in the development of these alloys. HEAs are known for their intricate compositions, offering a wide spectrum of material properties, making them particularly relevant for applications aimed at future sustainability. Phase engineering in HEAs unlocks the potential for creating materials tailored to eco-friendly technologies and energy-efficient solutions. The challenge in predicting phase selection in HEAs is accentuated by the limited data available on these complex materials. This review delves into how advanced data vetting techniques and ML algorithms are being employed to overcome these challenges, thus contributing significantly to sustainable material design. The paper examines various algorithms used in HEA phase prediction, including KNN (K-Nearest Neighbors), SVM (Support Vector Machines), ANN (Artificial Neural Networks), GNB (Gaussian Naive Bayes), and RF (Random Forest). It discusses the testing accuracy of these algorithms in classifying HEA phases, revealing variations in their effectiveness. The review highlights the superior accuracy of ANNs, followed closely by KNN and SVM, while noting the comparatively lower accuracy of GNB. This comprehensive review synthesizes current research efforts in utilizing computational methods to design HEAs, underlining their broader implications in expediting the discovery and development of diverse metal alloys. These efforts are pivotal in meeting the evolving demands of modern engineering applications, thereby contributing to the advancement of materials science.

Compositional regulation in additive manufacturing of precipitation-hardening (CoCrNi)94Ti3Al3 medium-entropy superalloy: Cellular structure stabilization and strength enhancement

High or medium-entropy alloys that feature high thermal stability and excellent oxidation resistance are promising candidates for elevated temperature applications. The rapid softening of monolithic high or medium-entropy alloys with single face-centered cubic structure at elevated temperatures, however, is a main weakness. In this paper, we report new high strength γ′-hardened ((CoCrNi)94Ti3Al3)98Nb2 medium-entropy alloy through laser powder-bed fusion (L-PBF) followed by ageing. In particularly, the tensile strengths of the aged ((CoCrNi)94Ti3Al3)98Nb2 alloy at 20 °C and 700 °C can reach up to 1.93 GPa and 1.11 GPa, respectively, 112 % and 122 % stronger than the as-built CoCrNi alloy tested at the same condition. A new strengthening mechanism, i.e., elemental segregation induced the cellular structure stabilization, in tandem with other hierarchical microstructure features, including ultrafine γ′ precipitates, dense twin boundaries, and other types of crystallized defects, co-contribute to the superb tensile strength at room and elevated temperatures. Such a simple alloy design and processing strategy outlines a guideline for designing novel multicomponent alloys and/or composites with superior microstructural stability and mechanical response at room and elevated temperatures.

Simultaneous improvement of mechanical and castability properties of Al-Cu-Mn based alloys by Ca/Ni micro-alloying

Currently one major barrier for the design of cast high-strength and high-toughness Al alloys is hot tearing. In this work, a strategy of combination of squeeze casting and microalloying (Ca/Ni eutectic elements) in Al-Cu-Mn based alloys was employed to inherit the excellent mechanical properties of Al-Cu alloys whilst simultaneously reducing their tendency to hot tearing. The developed alloys exhibit comparable castability (fluidity and hot tear resistance) to A356, which is widely available commercially. However, their comprehensive mechanical properties far exceed those of A356. Trace Ca/Ni additions markedly reduce the grain size of the alloy and simultaneously increase the fraction of intergranular low melting point eutectic liquid phases, which is beneficial to the improvement of liquid feeding. The fine equiaxed grains have excellent thermal shrinkage coordination, while the high volume fraction eutectic liquid phase delays the development of grain cohesive skeleton. Accordingly, the localized shrinkage stress/strain at the hot spot is released timely, thus inhibiting the emergence and propagation of hot cracks in the brittle solidification interval. The diminished hot tearing susceptibility is attributed to the reduced load onset temperature and load values in the hot spot region. A new intergranular bridging mechanism is discovered in low-Ca alloys: based on compositional segregation-induced nucleation of an intergranular bridging skeleton, which strengthens the intergranular adhesive force and effectively reduces the hot tearing tendency of the alloys. The alloys with high-Ca/Ni additions, however, reduce the hot tearing tendency by healing cracks through eutectic liquid phase backfill. The results of the hot tearing experiments of the developed alloys are analyzed with the current hot tearing evaluation criteria. The results demonstrate that the predictions of the Kou's criterion provide guidelines for the design of alloys that are resistant to hot tearing.

Dynamic Marine Atmospheric Corrosion Behavior of AZ91 Mg Alloy Sailing from Yellow Sea to Western Pacific Ocean.

In this work, the dynamic marine atmospheric corrosion behavior of AZ91 Mg alloy sailing from Yellow Sea to Western Pacific Ocean was studied. The corrosion rates were measured using the weight loss method. The microstructure, phase, and chemical composition of corroded samples were investigated by SEM, EDS, XRD, and XPS. The results show that the evolution of corrosion rates of AZ91 Mg alloy was divided into three stages: rapidly increasing during the first 3 months, then remaining stable for the next three months, and finally decreasing after 6 months. The annual corrosion rate of Mg alloy reached 32.50 μm/y after exposure for 12 months in a dynamic marine atmospheric environment, which was several times higher than that of the static field exposure tests. AZ91 magnesium alloy was mainly subjected to localized corrosion with more destructiveness to Mg parts, which is mainly due to the synergistic effect of high relative humidity, the high deposition rate of chloride ion, sulfur dioxide acidic gas produced by fuel combustion, and rapid temperature changes caused by the alternating changes in longitude and latitude during navigation. As the exposure time increased, the corrosion pits gradually increased and deepened. The maximum depth of the corrosion pit was 197 μm after 12 months of exposure, which is almost 6 times the average corrosion depth. This study provides scientific data support for the application of magnesium alloys in shipborne aircraft and electronic equipment. The results could provide guidance for the design of new magnesium alloys and development of anti-corrosion technologies.

Highly efficient photocatalytic hydrogen generation of PtPdy nanoframe/2D-CdS: Shape-controlled preparation and property modulation

This work focuses on the structure design of Pt-based alloys, and their influences on 2D-CdS semiconductor photocatalyst in hydrogen (H2) generation reaction from water-splitting under visible light, using traditional experimental techniques and DFT calculations as Pd concave nanocube (Pd CNCs) as a template, PtPdx alloy with cuboctahedron core-shell structure (PtPdx NPs) and cuboctahedron nanoframe (PtPdy NFs) were successfully synthesized via wet chemical routes. The structure of Pt-based alloys was certified by XRD, HRTEM, XPS, and ICP. The Pt-based co-catalysts were photo-deposited on 2D-CdS in an aqueous solution of (NH4)2SO3 while the reaction for photo-generating of H2 occurred. The obtained photocatalysts show excellent activity towards hydrogen generation, i.e., in ascending order, Pd CNCs/2D-CdS (46.1 mmol/h/g) < PtPd1.8 NPs/2D-CdS (55.4 mmol/h/g) < PtPd0.2 NFs/2D-CdS (71.7 mmol/h/g, QE=61.46%, λ=420 nm). Photoelectrochemical tests, ESR, and work functions results indicate that PtPd0.2 NFs have excellent photoelectrochemical performance, the longest lifetime of electrons, and the highest work function, respectively. Moreover, DFT calculations unveil that PtPd0.2 has the largest surface energy and the lowest activation energy ΔGH* which results in the fast charge transfer rate at the PtPd0.2/2D-CdS interface. This work offers a novel thought into the structural design of Pt-based co-catalysts applied in photocatalytic hydrogen generation from water-splitting.