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• The hugoniot elastic limit (HEL) and the spalling strength (σ sp) were measured as 7.09 GPa and 2.28 GPa. • The failure mode changed from spallation to fragmentation caused by the combination of spalling cracks and longitudinal cracks. • The elastic wave front causes pre-damage to the BMG, leading to a decrease in its spalling strength. Dynamic response and damage evolution of Zr 70 Cu 13 Ni 9.8 Al 3.6 Nb 3.4 Y 0.2 bulk metallic glass (Zr-based BMG) under impact pressure ranging from 4.03 GPa to 27.22 GPa were studied. The Hugoniot Elastic Limit (HEL) and the spalling Strength (σ sp) were measured as 7.09 GPa and 2.28 GPa, and the curve of impact velocity (D) and particle velocity (u) were also obtained. Under the strain rate of ~105 s−1, local crystallization phenomenon was observed. As increasing the impact pressure, the failure mode of Zr-based BMG changed from spallation to fragmentation caused by the combination of spalling cracks and longitudinal cracks. Cone-cup structures were also observed in the internal spalling zone via nano-CT characterization. When increasing the impact pressure, the thickness of Zr-based BMG increased after impact and the remelting and cladding layers were also observed on the fracture surfaces. The fragments of the specimen were welded after impact due to the high temperature remelting, which causes plastic deformation of Zr-based BMG under shock loading. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Beta phase to omega and martensitic transformation through mechanical form of driving force. • Deformation through activation of slips and twins after quasi-static and dynamic compression. • Crystal rotation, grain boundary sliding, spalling & cracking, and shear band formation. Most of the structural alloys' applications are under static, dynamic, and cyclic forms of loading. Ti-5553 alloy in the beta phase field is being investigated to confirm the mechanism of deformation and phase transformation upon quasi-static and dynamic compression. The Ti-5553 alloy was heat-treated at 900 °C (almost 50 °C above beta transus temperature) for one hour of soaking time followed by air quenching to achieve a fully β phase field. After that, Dynamic compression (DC) by Split Hopkinson Pressure Bar (SHPB) and Quasi-static compression (QSC) were performed at a strain rate of ̴103/s and 10−3/s, respectively. Recovered specimens were thoroughly examined by using different tools, such as an Optical microscope (OM), Scanning electron microscope (SEM), High-resolution transmission electron microscope (HRTEM), and Electron backscatter diffraction (EBSD) to get the reliable data for justification of logical conclusions. It is found that the dominating mode of deformation was dislocation slip along with twinning ({332} <113>) to some extent in both of QSC and DC, but sliding & spalling of the grain boundary is observed more in the former. Stress-induced phase transformation, i.e., β to α" and β to ω, took place in the grains saturated with dislocation slips, where the former transformation occurred simultaneously with {332} <113> twinning, while β to ω transformation was completed when a set of two adjacent (110)ᵦ planes covered ±1/6th of the total separation distance between two (next to each other) (111)ᵦ planes, by equal but opposite shear in (111)ᵦ direction, and it caused 3% shrinkage of two closed packed (110)ᵦ planes after transformation. [ABSTRACT FROM AUTHOR]

Most recently, high-entropy alloys (HEAs) with 5 or more elements open a new area for materials exploration with substantial mechanical properties. The large composition space and numerous structures of HEAs bring significant difficulties for phase design and determination of mechanical property. Machine learning, one of most rapidly growing scientific and technical field, meets at the intersection of computer science and materials science, and at the center of artificial intelligence. Machine learning provides the opportunity to build up the relationship between multiple physical properties and mechanical properties. The fast changes of this field call for significant practice for materials community to utilize it as a more efficient, accurate and interpretable tool. In this review, we summarize the most promising machine learning models, combined with high-throughput simulation and experimental screening, to predict and fabricate HEAs with desired superb mechanical properties.

In this paper, the mechanical properties, work hardening characteristics and deformation mechanism of lean duplex stainless steel (LDSS) S32101 produced by direct cold rolling were studied under different temperature conditions. The yield strength (YS) and tensile strength (TS) of S32101 decreased with the increase of deformation temperature, while the elongation increased first and then decreased. The TS of S32101 at -70 °C was 1052.6 MPa, the elongation remained 57.2%, and the product of strength and elongation (PSE) was as high as 60.2 GPa·%, which was mainly due to the synergistic strengthening of transformation induced plasticity (TRIP) and twinning-induced plasticity (TWIP) effects in austenite at cryogenic temperatures. The efficiency of grain refinement at cryogenic temperature was improved by TRIP effect and deformation twins (DTs), indicating that it had the potential to be applied at low temperature (-70 ∼ -30 °C). Moreover, the high density nanotwins and the strong interaction between the dislocation and nanotwin bundles also contributed to strain hardening at low temperatures and thus better comprehensive mechanical properties could be achieved.

Fe on CeO2, inheriting the oxygen storage/release capacity of ceria and the catalytic activity of Fe with various d orbitals, has been widely used in heterogeneous catalysis. To explore the morphological and electronic structures of the ceria supported iron model catalyst, we employed X-ray photoelectron spectroscopy (XPS), synchrotron radiation photoemission spectroscopy (SRPES), scanning tunneling microscopy (STM), and low energy electron diffraction (LEED) to comprehensively investigate the growth, structure, and thermal stability of Fe deposited onto 3 nm thick well-ordered CeO2(111) thin films grown on Cu(111) at room temperature. At low coverage, Fe clusters tend to a two-dimensional random growth on CeO2(111). Charge transfer occurs between Fe and CeO2(111), leading to the oxidation of Fe to Fe2+and reduction of Ce4+to Ce3+. The average charge per Fe atom and local surface dipole indicate the formation of Fe–O–Ce mixed oxides instead of FeO at the interface. Notably, an unprecedented (2/3× 2/3)-R30° wetting layer can be identified at high Fe coverage at 420 K. The evolutions of electronic and morphological structures of Fe on CeO2(111) provide deep insight into the metal–support interactions.

Al-Mg-Si alloys fabricated by additive manufacturing (AM) are known to suffer from the coarse columnar microstructure, which usually causes severe hot cracking and anisotropy in mechanical properties. Introducing potent nucleants to promote columnar to equiaxed transition (CET) is an efficient method to solve this problem. However, nanoscale nucleant particles are prone to agglomerate and form clusters during high-temperature AM, which are detrimental to the ductility. In this work, in the AA6061 fabricated by directed energy deposition (DED), we designed a novel approach to alleviate the agglomeration of TiB2particles by adopting interlayer pause (IP) strategy on the basis of TiB2nucleant addition. Resultantly, due to the discontinuous heat input interrupted by IP and thus a reduced heat accumulation, dispersed fine TiB2particles can be achieved, which reduce the stress concentration and allow for a good metallurgical binding. Moreover, these dispersed fine TiB2particles, (a) effectively promote the CET by providing numerous heterogeneous nucleation sites, resulting in an ultra-fine fully-equiaxed grain microstructure (~ 21 μm) with a reduced texture; (b) significantly inhibit the formation of pores, reducing both their density and size. Consequently, crack-free high-performance DEDed AA6061 without anisotropy in mechanical properties are successfully fabricated, achieving high strength and high ductility at T6-treated state along both the vertical direction (YS: 266 ± 2MPa, EL: 8 ± 1%) and the horizontal direction (YS: 262 ± 2MPa, EL: 7 ± 1%), simultaneously. This combination of nucleant addition and deliberately-controlled IP strategy is expected to be applicable to a wide range of wrought aluminum alloys (e.g. 2xxx and 7xxx) fabricated by AM.

Bimetallic catalysts typically exhibit superior activity and selectivity compared to single-component catalysts when optimized, inspiring a detailed understanding of the properties of the complex system. Herein, we employed high-resolution X-ray (including synchrotron-based) photoelectron spectroscopy and infrared reflection absorption spectroscopy measurements using CO as the probing molecule to investigate the surface structure of ceria-supported CoCu bimetallic nanoparticles. We found that Co deposition on a Cu-precovered CeO2surface induces Cu migration to the surface, accompanied by ceria reduction and interfacial Co/CeO2formation. The lower surface energy of copper than that of cobalt and the stronger interaction of CeO2with Co than with Cu are possibly responsible for this surface dynamic evolution. This surface structure can be modulated by the introduction of oxygen. A small amount of oxygen exposure effectively promotes the reconstruction of the surface structure by Co migration to the surface of Co/Cu/CeO2, forming cobalt oxides. Our combined spectroscopic results provide direct evidence of the surface structure evolution of CeO2-supported bimetallic nanoparticles under certain conditions.