Zhaoping Lu

Phase‐Transformation Ductilization of Brittle High‐Entropy Alloys via Metastability Engineering

High-entropy alloys (HEAs) in which interesting physical, chemical, and structural properties are being continuously revealed have recently attracted extensive attention. Body-centered cubic (bcc) HEAs, particularly those based on refractory elements are promising for high-temperature application but generally fail by early cracking with limited plasticity at room temperature, which limits their malleability and widespread uses. Here, the metastability-engineering strategy is exploited in brittle bcc HEAs via tailoring the stability of the constituent phases, and transformation-induced ductility and work-hardening capability are successfully achieved. This not only sheds new insights on the development of HEAs with excellent combination of strength and ductility, but also has great implications on overcoming the long-standing strength-ductility tradeoff of metallic materials in general.

Microstructural Control via Copious Nucleation Manipulated by In Situ Formed Nucleants: Large-Sized and Ductile Metallic Glass Composites

A novel strategy to control the precipitation behavior of the austenitic phase, and to obtain large-sized, transformation-induced, plasticity-reinforced bulk metallic glass matrix composites, with good tensile properties, is proposed. By inducing heterogeneous nucleation of the transformable reinforcement via potent nucleants formed in situ, the characteristics of the austenitic phase are well manipulated.

Shock compression response of high entropy alloys

ABSTRACT In this work, we studied the shock response of two typical equiatomic high entropy alloys (HEAs) (i.e. FCC-structured CrMnFeCoNi alloy and BCC-structured NiCoFeCrAl alloy). The experimental results show that these two HEAs exhibit a relatively high Hugoniot elastic limit and high-phase transition threshold stress. We attribute this anomalous dynamic response of HEAs to their intrinsic chemically disordered structures. This work may provide new insight into shock compression behavior of HEAs. IMPACT STATEMENT This is the first work to demonstrate that high entropy alloys (HEAs) behave ‘super-stably’ under shock loading, which may provide new insight into shock compression behavior of HEAs. GRAPHICAL ABSTRACT

Thermoelectric performance of PbSnTeSe high-entropy alloys

ABSTRACT In our study, we designed the PbSnTeSe high-entropy alloy (HEA) and investigated its microstructure and thermoelectric properties. It was found that the PbSnTeSe HEA has a simple face-centered cubic structure and possesses quite low lattice thermal conductivity at low temperatures, which could be ascribed to the strong phonon scattering due to its severe lattice-distortion. Minor additions of La not only enhanced both Seebeck coefficient and electrical conductivity at high temperatures, but also suppressed the bipolar effect to some degree. Our results indicate that the HEA concept could be applied for developing promising thermoelectric materials, which merits further investigation. GRAPHICAL ABSTRACT IMPACT STATEMENT The high-entropy alloy-design concept was employed to develop novel thermoelectric materials. Our findings indicate that this strategy effectively reduced the lattice thermal conductivity, which have important implications for the field.

Coating thickness control in continuously fabricating metallic glass-coated composite wires

A continuous production process was developed for coating bulk metallic glasses on the metallic wire surface. The effects of processing parameters, including the drawing velocity and coating temperature, on the coating thickness were investigated. It is found that the coating thickness increases with the increase in drawing velocity but decreases with the increase in coating temperature. A fluid mechanical model was developed to quantify the coating thickness under various processing conditions. By using this theoretical model, the coating thickness was calculated, and the calculated values are in good agreement with the experimental data.

High-performance hybrid electrode decorated by well-aligned nanograss arrays for glucose sensing

The worldwide boost in glucose related diseases such as diabetics over the last decade leads to an overwhelming demand for development of advanced electrochemical glucose sensors with high sensitivity, fast response and excellent selectivity. Herein we report a novel freestanding microelectrode comprising well-aligned Cu(OH)2 nanograss arrays and uniform nanoporous copper (NPC) substrate. Such a cost-effective hierarchical hybrid structure entails a unique combination of good conductivity of NPC and high electrocatalytic activity of Cu(OH)2. As a result, the glucose sensor based on the hybrid nanostructure exhibits extraordinary performance towards the oxidation of glucose with a high sensitivity of ~2.09mAcm-2mM-1, wide linear range of 0.2-9mM, low detection limit of 197nM, fast response time of less than 1s and excellent selectivity. The current work not only provides novel hybrid materials with great potential to be commercialized in blood glucose sensing, but also has important implications for designing enhanced nanostructured electrocatalysts for engineering applications in general.

Delayed plasticity during nanoindentation of single-phase CoCrFeMnNi high-entropy alloy

ABSTRACT Spherical nanoindentation was performed at room temperature to characterize the time-dependent plasticity behavior of the single-phase CoCrFeMnNi high-entropy alloy (HEA). It was observed that incipient plasticity occurred after a period of waiting time in the apparent elastic regime. Through the experimental data, an activation energy ∼0.74u2009eV and an activation volume ∼1.54b3 (bu2009=u2009Burgers vector) were extracted for the delayed plasticity. Our results indicate that heterogeneous dislocation nucleation governs the delayed plasticity in the single-phase CoCrFeMnNi, and also provide quantitative insights into viscoplastic behavior and creep mechanisms in HEAs. GRAPHICAL ABSTRACT IMPACT STATEMENT The delayed plasticity behavior was studied in single-phase FCC CoCrFeMnNi HEA. Our results indicate that heterogeneous dislocation nucleation governs the delayed plasticity behavior.

Influences of Au ion radiation on microstructure and surface-enhanced Raman scattering of nanoporous copper

In this work, effects of Au ion irradiation on microstructure and surface-enhanced Raman scattering (SERS) performance of nanoporous copper (NPC) were investigated. It is found that the microstructure of NPC could be tailored by the ion irradiation dose, i.e., the pore size decreases while the ligament size significantly coarsens with the increase of the irradiation dose. In addition, the SERS enhancement for rhodamine 6G molecules was improved by Au ions irradiation at an appropriate dose. The underlying mechanism of the increase of SERS enhancement resulted from ion irradiation was discussed. Our findings could provide a new way to tune nanoporosity of nanoporous metals and improve their SERS performance.

Ion Irradiation-Enhanced Raman Scattering on Nanoporous Copper

Nanoporous copper (NPC) is the potential affordable surface-enhanced Raman scattering (SERS) substrate in practical use, although restricted by a relatively small enhancement factor. In this report, Cu ion irradiation is applied to effectively increase the enhancement factor of NPC. Two levels of surface roughness in NPC after ion irradiation are proposed to account for the improved SERS effect by careful characterization of microstructures. This study provides a new strategy to acquire a higher Raman enhancement factor in NPC, which perhaps can be extended to other SERS substrate systems.