Glass Forming Ability of Metallic Glasses Evaluated by a New Criterion

The glass-forming ability （GFA） of Cu-Zr binary alloys is evaluated using the existing criteria based on calorimetric parameters, and poor relations are found. Therefore, another parameter Tτκ defined as Tκ/Tl, in which Tκ is the Kauzmann temperature and Tl the equilibrium liquidus temperature, is proposed. It exhibits good agreements with the experimental data of the Cu-Zr system and other representative bulk metallic glass formers so long as classifying them into strong or fragile category. It is suggested that kinetic effects are irrelevantly incorporated in the GFA analysis in the previous work.

Structural,curvature and electronic properties of Rh adsorption on armchair single-walled carbon nanotube

This paper systematically studies the rolling effects of the （n, n） single-wall carbon nanotubes （SWCNT） with different curvatures on Rh adsorption behaviours by using density functional theory. The outside charge densities of SWCNTs are found to be higher than those inside, and the differences decrease with the increase of the tube radius. This electronic property led to the discovery that the outside adsorption energies are higher than the inside ones, and that the differences are reduced with the increase of the tube radius. Partial density of states and charge density difference indicate that these strong interactions induce electron transfer between Rh atoms and SWCNTs.

Finite size effect on the Raman frequency of phonons in nano-semiconductors

A comprehensive study on Raman spectroscopy with different excitation wavelengths, sample sizes, and sample shapes for optic phonons （OPs） and acoustic phonons （APs） in polar and non-polar nano-semiconductors has been performed. The study affirms that the finite size effect does not appear in the OPs of polar nano-semiconductors, while it exists in all other types of phonons. The absence of the FSE is confirmed to originate from the long-range FrShlieh interaction and the breaking of translation symmetry. The result indicates that the Raman spectra of OPs cannot be used as a method to characterize the scale and crystalline property of polar nano-semiconductors.

Novel Co-free high performance TRIP and TWIP medium-entropy alloys at cryogenic temperatures

Recently,high-and medium-entropy alloys(HEAs and MEAs) have been found to exhibit excellent cryogenic mechanical properties,but most of them contain high-priced Co element.Therefore,developing HEAs or MEAs with high strength and ductility and relatively low cost is urgent.In this work,novel Cofree Fex Mn(75-x) Ni(10)Cr(15)(x=50 and 55 at.%) MEAs were developed,which exhibit a good combination of low cost,high strength and ductility at cryogenic temperature.It was found that the Fe(50)Mn(25)Ni(10)Cr(15)MEA exhibits a combination of cryogenic tensile strength of^0.98 GPa and ductility of^83 %.The excellent cryogenic mechanical properties were attributed to joint of twinning-induced plasticity(TWIP) and transformation-induced plasticity(TRIP) effects.The present study sheds light on developing low cost MEAs with high perfo rmance for cryogenic-tempe rature applications.

Tunability of the mechanical properties of(Fe_(50)Mn_(27)Ni_(10)Cr_(13))_(100-x)Mo_(x) high-entropy alloys via secondary phase control

The single-phase face-centered cubic(fcc)-structured Fe_(50)Mn_(27)Ni_(10)Cr_(13) high entropy alloy(HEA)exhibits good ductility but low strength,which presents a challenge.By Mo-alloying and thermomechanical treatments,we have designed the(Fe_(50)Mn_(27)Ni_(10)Cr_(13))_(100-x)Mo_(x)(x=0-6 at.%)alloy series with a wide range of mechanical properties.The careful control of secondary phases introduced in the cold-rolled and annealed(Fe_(50)Mn_(27)Ni_(10)Cr_(13))Mo_(2) sample resulted in an enhanced tensile strength from 250 MPa to 665 MPa,still having~25%ductility.TEM investigations of this alloy revealed the presence of deformation twins,dislocation cells,and ordered bcc na no-pa rticles embedded in the ductile fcc matrix post-deformation.The observed deformation structures are an indication of succes s ful cooperation between deformation twinning and precipitation strengthening in enhancing the tensile strength at maintained ductility compared to its cast counterpart.This work provides insight into the tunability of the mechanical properties of non-equiatomic HEAs via alloying and thermomechanical processing.

High pressure X-ray diffraction study of CaMnO_3 perovskite

Using a diamond anvil cell device and synchrotron radiation,the in-situ high-pressure structure of CaMnO3 has been investigated.In the pressure up to 36.5 GPa,no pressure-induced phase transition is observed.The pressure dependence on the lattice parameters of CaMnO3 is reported,and the relationship of the axial compression coefficients is βa 〉 βc 〉 βb.The isothermal bulk modulus K298=224（25） GPa is also obtained by fitting the pressure-volume data using the Murnaghan equation of state.

Toughening FeMn-based high-entropy alloys via retarding phase transformation

Various high entropy alloys(HEAs)with improved mechanical properties were developed by reducing the phase stability and then promote the phase transformation.The promotion of deformation-induced ma rtensitic transformation from face-centered cubic(fcc)to hexagonal close-packed(hcp)mostly focuses on overcoming the trade-off of strength-ductility of HEAs at room temperature.However,the hcp phase is brittle at cryogenic-temperature,and thus the enhancement of cryogenic ductility of these HEAs still remains a challenge.Here,we present a concept to toughening Fe50Mn30Co10Cr10 HEAs at cryogenictemperature via retarding phase transformation.The retarded but more persistent phase transformation at high strain level was realized via tailoring the grain size.To further verify the effect of phase transformation rate on ductility of HEAs,the mechanical properties of Fe40Mn40Co10Cr10 HEAs with higher stacking fault energy were tested at room and cryogenic temperature,respectively.The present study sheds light on developing high perfo rmance HEAs,especially for alloys with brittle phase transformation products.

High pressure X-ray diffraction study of SrMnO_3 perovskite

Using a diamond anvil cell device and synchrotron radiation, the in-situ high-pressure structure of SrMnO 3 has been investigated. At pressure up to 28.6 GPa, no pressure-induced phase transition is observed. The lattice parameters as a function of pressure is reported, and the relationship of the axial compression coefficients is β a 〉 β c . The isothermal bulk modulus K 298 =266（4） GPa is also obtained by fitting the pressure- volume data using the Murnaghan equation of state.

Mechanical property and structural changes by thermal cycling in phase-separated metallic glasses

Nondestructive cryogenically thermal cycling has been a simple but effective treatment to enhance mechanical properties of glassy materials.However,how the structural heterogeneities on nanometer scales are affected by thermal cycling is still an issue.Here,we report the response of spatial heterogeneities in three selected Ti_(41)Zr_(25)Be_(28)Fe_(6),Zr_(56)Co_(14)Cu_(14)Al_(16)and Zr_(42)Y_(14)Co_(22)Al_(22)(at.%)metallic glasses(MGs)with different compositions to the thermal cycling,which show significantly different structure and properties after the same treatments and could be ascribed to the joint contribution of relaxation and rejuvenation induced by thermal cycling.The rejuvenation is initially prevailed in a Zr-Y-containing MG,whereas the relaxation is dominant in a Cu-Co-containing MG,both eventually entering into a dynamic equilibrium state.By employing nanometer-scale structural models,the intrinsic correlation between the spatial heterogeneity and thermal cycling is proposed.The discovery could provide the fundamental understanding of the role of spatial heterogeneity in influencing the macroscopic properties of MGs via thermal cycling and help design high-performance glassy materials by tailoring their atomic structures with suitable thermal treatments.