The hot deformation behaviors of Al–Mg–Mn 5xxx alloys with different Mn contents (0.1–1 wt.%) were studied by carrying out uniaxial compression tests over the temperature and strain rate ranges of ...350–500 °C and 0.001–1.0 s−1, respectively. In the pre-deformed state, Mn dispersoids appeared in the α-Al matrix once the Mn content reached 0.4%. The density of these dispersoids increased with a further increase in the Mn content. The peak flow stress gradually increased with an increase in the Mn content under a given deformation condition owing to the strong strengthening effect of the dispersoids, and the activation energy of hot deformation also increased with increasing Mn content. The deformed microstructures were analyzed using the electron backscatter diffraction technique, and the dominant restoration mechanisms were classified based on the Zener-Hollomon parameter (Z). Under low-Z deformation conditions, continuous dynamic recrystallization (CDRX) was the principal softening mechanism. At intermediate Z values, CDRX was partially accompanied by particle-stimulated and discontinuous DRX. At higher Z values, dynamic recovery was the only softening mechanism, which was mainly dominated by work hardening.
In the present work, the effects of magnesium and silicon addition on microstructure, elevated-temperature yield strength and creep resistance of Al-Mn-Mg 3xxx alloys were investigated. The ...microstructure evolution under as-cast and heat-treated conditions was quantitatively evaluated by optical and electron microscopy. Results revealed that both magnesium and silicon had an important influence on the distribution and volume fraction of precipitated dispersoids in 3xxx alloys. Without Mg or Si addition, dispersoids could hardly form during the precipitation heat treatment; hence, the alloys free of Mg or Si possessed low yield strength and creep resistance at elevated temperature. A significant improvement in elevated-temperature yield strength and creep resistance was obtained over a wide range of Mg (0.5–1.5wt%) and Si (0.25–1wt%) content studied due to the precipitation of a large number of dispersoids. The best combination of yield strength and creep resistance at 300 ℃ was obtained by the alloy containing 1.0wt% Mg and 0.25wt% Si with the maximum volume fraction of dispersoids and the minimum volume fraction of dispersoid free zone. The effects of dispersoid strengthening, solid solution strengthening and grain size on yield strength and creep resistance were discussed based on experimental results.
We investigate the current-induced switching of the Néel order in NiO(001)/Pt heterostructures, which is manifested electrically via the spin Hall magnetoresistance. Significant reversible changes in ...the longitudinal and transverse resistances are found at room temperature for a current threshold lying in the range of 10^{7} A/cm^{2}. The order-parameter switching is ascribed to the antiferromagnetic dynamics triggered by the (current-induced) antidamping torque, which orients the Néel order towards the direction of the writing current. This is in stark contrast to the case of antiferromagnets such as Mn_{2}Au and CuMnAs, where fieldlike torques induced by the Edelstein effect drive the Néel switching, therefore resulting in an orthogonal alignment between the Néel order and the writing current. Our findings can be readily generalized to other biaxial antiferromagnets, providing broad opportunities for all-electrical writing and readout in antiferromagnetic spintronics.
Ten years have passed since the conception of what was termed Lewis pair polymerization (LPP) that employs Lewis acid and base in pairs to not only activate monomers but also effect chain initiation, ...propagation, and transfer events. Compared to other polymerization methodologies, LPP’s cooperative and synergistic two-component catalytic mechanism empowers several unique or advantageous features, including extraordinary tunability of catalyst/initiator systems, compounded thermodynamic and kinetic control over comonomer sequences in one-pot LPP of monomer mixtures for highly resolved block copolymers, complete chemoselectivity in LPP of multifunctional vinyl monomers, independent tuning of polymerization activity and target polymer molecular weight, controlled heat dissipation in bulk polymerization with unactivated monomers functioning as solvent molecules, and coupled selectivity and livingness with immortality of the active species to produce ultrahigh molecular weight polymers and block copolymers with record-number (53) blocks. Focusing on four fundamental attributes of any polymerization methodologymechanism, kinetics, control, and selectivitythis Perspective narrates the growth and development of LPP, tracing each innovation back to fundamental principles so that each concept can be strategically applied, and describes new frontiers fertile for future research.
Precision synthesis of cyclic polymers with predictable molecular weight and low dispersity is a challenging task, particularly concerning cyclic polar vinyl polymers through a rapid chain-growth ...mechanism and without high dilution. Harder yet is the precision synthesis of cyclic block copolymers (cBCPs), ideally from comonomer mixtures. Here we report that Lewis pair polymerization (LPP) capable of thermodynamically and kinetically compounded sequence control successfully addressed this longstanding challenge. Thus, LPP of acrylate/methacrylate mixtures under ambient temperature and normal concentration conditions rapidly and selectively affords well-defined cBCPs with high molecular weight (M n = 247 kg/mol) and low dispersity (Đ = 1.04) in one step. Such cBCPs have been characterized by multiple techniques, including direct structural observation by imaging.
Various surface characterization techniques were used to study the modified surface chemistry of superhydrophobic aluminum alloy surfaces prepared by immersing the substrates in an aqueous solution ...containing sodium hydroxide and fluoroalkyl-silane (FAS-17) molecules. The creation of a rough micronanostructure on the treated surfaces was revealed by scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) and infrared reflection absorption spectroscopy (IRRAS) confirmed the presence of low surface energy functional groups of fluorinated carbon on the superhydrophobic surfaces. IRRAS also revealed the presence of a large number of OH groups on the hydrophilic surfaces. A possible bonding mechanism of the FAS-17 molecules with the aluminum alloy surfaces has been suggested based on the IRRAS and XPS studies. The resulting surfaces demonstrated water contact angles as high as ∼166° and contact angle hystereses as low as ∼4.5°. A correlation between the contact angle, rms roughnesses, and the chemical nature of the surface has been elucidated.
Coordination polymerization of polar vinyl monomers by single-site metal catalysts is discussed. This process has resulted in precise control of molecular structure, along with the creation of new ...classes of materials.
Triple-negative breast cancer (TNBC) is a collection of biologically diverse cancers characterized by distinct transcriptional patterns, biology, and immune composition. TNBCs subtypes include two ...basal-like (BL1, BL2), a mesenchymal (M) and a luminal androgen receptor (LAR) subtype. Through a comprehensive analysis of mutation, copy number, transcriptomic, epigenetic, proteomic, and phospho-proteomic patterns we describe the genomic landscape of TNBC subtypes. Mesenchymal subtype tumors display high mutation loads, genomic instability, absence of immune cells, low PD-L1 expression, decreased global DNA methylation, and transcriptional repression of antigen presentation genes. We demonstrate that major histocompatibility complex I (MHC-I) is transcriptionally suppressed by H3K27me3 modifications by the polycomb repressor complex 2 (PRC2). Pharmacological inhibition of PRC2 subunits EZH2 or EED restores MHC-I expression and enhances chemotherapy efficacy in murine tumor models, providing a rationale for using PRC2 inhibitors in PD-L1 negative mesenchymal tumors. Subtype-specific differences in immune cell composition and differential genetic/pharmacological vulnerabilities suggest additional treatment strategies for TNBC.
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