激光焊接及焊后热处理K439B合金的显微组织与力学性能

对应用于发动机涡轮上的新型镍基合金K439B进行激光焊接实验,研究焊后热处理对接头显微组织和力学性能的影响。半定量分析结果表明,热处理后接头各区域γ′相均发生长大,一次γ′相和二次γ′相半径分别约为25和150 nm。力学性能测试结果表明,焊后热处理可使焊缝区硬度提高约HV 100,由γ′相提供的临界恢复剪应力从4.8 MPa提高到92 MPa;另一方面,热处理后接头的抗拉强度和屈服强度与母材的相当,大量碳化物的存在导致接头在拉伸过程中优先断裂于母材处。

Microstructure characteristics and thermodynamic properties of A357-SiCp/A357 layered composites prepared by semi-solid vacuum stirring suction casting

A357-SiCp/A357 layered composites were prepared using a semi-solid vacuum stirring suction casting method.The microstructures,mechanical properties,and thermal conductivities of the composites fabricated under different suction casting processes were compared.Additionally,the microstructural evolution characteristics and performance enhancement mechanism of the A357-SiCp/A357 layered composites were discussed.The results demonstrate that suction casting at 610°C with a low solid phase ratio can significantly enhance the material density and reduce the agglomeration of SiCp.The A357-SiC_(p)/A357 interface is clear and straight with good bonding.With an increase in the suction casting temperature,the bending resistance and thermal conductivity of the A357-SiC_(p)/A357 layered composites exhibit a trend of significantly increase at first and then slowly decrease owing to casting defects,interface bonding,and SiCp distribution.Compared with SiCp/A357 composites,the bending strength,deflection,and thermal conductivity of the A357-SiCp/A357 layered composites increase from 257 MPa,1.07 mm,and 155.72 W·(m·K)^(-1) to 298 MPa,2.1 mm,and 169.86 W·(m·K)^(-1),respectively.This study provides a reference for improving the rheological casting of aluminum matrix layered composites.

Microstructure and mechanical properties of laser beam welded TC4/TA15 dissimilar joints

The microstructure and mechanical properties of laser beam welded dissimilar joints in TC4 and TA15 titanium alloyswere investigated. The results showed that the coarse columnar grains containing a large amount of acicular α and martensite α′ werepresent in the fusion zone (FZ), some residual α phases and martensite structure were formed in the heat-affected zone (HAZ) onTC4 side, and bulk equiaxed α phase of the HAZ was on TA15 side. An asymmetrical microhardness profile across the dissimilarjoint was observed with the highest microhardness in the FZ and the lowest microhardness in TA15 BM. The orders of yield strengthand ultimate tensile strength were as follows: TC4 BM > TC4/TC4 similar joint > TA15 BM > TA15/TA15 similar joint > TC4/TA15dissimilar joint, and increased while hardening capacity and strain hardening exponent decreased with increasing strain rate from1×10?4 s?1 to 1×10?2 s?1. The TC4/TA15 dissimilar joints failed in the TA15 BM, and had characteristics of ductile fracture atdifferent strain rates.

Experimental and Density Functional Theory Calculation Studies on Raman and Infrared Spectra of 1,1＇-Binaphthyl-2,2＇-diamine

The IR absorption, visible excited normal Raman, and UV-excited near-resonant Raman （UVRR） spectra of 1,1＇-binaphthyl-2,2＇-diamine （BINAM） were measured and analyzed. Density functional theory calculations were carried out to investigate its vibrational frequencies, infrared absorption, normal Raman, and near-resonance Raman intensities. The observed Raman and IR bands of BINAM were assigned with respect to the local vibrations of substituted 2-naphthylamine. Several Raman bands of BINAM were found selectively enhanced in the UVRR in comparison with the normal Raman spectrum. Possible excited state geometry distortion was discussed based on the resonance Raman intensity analysis.

KSSOLV-GPU:an Efficient GPU-Enabled MATLAB Toolbox for Solving the Kohn-Sham Equations within Density Functional Theory in Plane-Wave Basis Set

KSSOLV(Kohn-Sham Solver)is a MATLAB(Matrix Laboratory)toolbox for solving the Kohn-Sham density functional theory(KS-DFT)with the plane-wave basis set.In the KS-DFT calculations,the most expensive part is commonly the diagonalization of Kohn-Sham Hamiltonian in the self-consistent field(SCF)scheme.To enable a personal computer to perform medium-sized KS-DFT calculations that contain hundreds of atoms,we present a hybrid CPU-GPU implementation to accelerate the iterative diagonalization algorithms implemented in KSSOLV by using the MATLAB built-in Parallel Computing Toolbox.We compare the performance of KSSOLV-GPU on three types of GPU,including RTX3090,V100,and A100,with conventional CPU implementation of KSSOLV respectively and numerical results demonstrate that hybrid CPU-GPU implementation can achieve a speedup of about 10 times compared with sequential CPU calculations for bulk silicon systems containing up to 128 atoms.

Prevalence of osteoporotic vertebral fracture among community-dwelling elderly in Shanghai

To the Editor:Osteoporosis is becoming a common,serious,and costly health problem,which causes over nine million fractures annually worldwide.[1] Currently,osteoporotic fractures are a considerable burden to public health services and have fairly high morbidity and mortality.[2] Vertebral fractures are the most common osteoporotic fracture and may lead to a high risk of further fracture and could be prevalent in both females and males.[3] Ling et al[4] and Ms.OS studies[5] evaluated the prevalence of vertebral fractures in Beijing and Hong Kong,respectively.However,our knowledge of the descriptive epidemiology and risk factors for vertebral fracture in China still remains poor.

Consensus on clinical management of tumor-induced osteomalacia

Tumor-induced osteomalacia(TIO)is a rare paraneoplastic syndrome caused by excessive fibroblast growth factor 23(FGF23)production by a tumor,which often arises from a mesenchymal origin.[1-3]Most clinical symptoms of TIO are the consequences of prolonged FGF23-mediated hypophosphatemia as muscle weakness,bone pain,impaired mobility,and fractures.[4]Clinical diagnosis and management of TIO are challenging because knowledge about this condition is still restricted to a few specialized centers,leading to delay in diagnosis and appropriate treatment.The scope of the present consensus is to provide up-to-date guidance on the assessment and treatment of TIO.

Effects of molecular configuration of a chiral trimeric phenylene vinylene on its liquid crystalline properties

Based on an analysis of the 1H NMR,FT-IR,UV-vis spectra,a chiral trimeric phenylene vinylene derivative（ChTPV） synthesized by a Wittig reaction was determined to have a trans-cis configuration, and it could be isomerized to the trans-trans isomer when treated with iodine.The melting point of ChTPV with a trans-trans configuration increased by 162.1℃compared to the trans-cis isomer,and the ChTPV with trans-trans configuration exhibited the typical liquid-crystalline texture of the smectic A in the heating process.The results indicated that the molecular configuration can influence the formation of the liquid crystalline phase of ChTPV.

Synthesis,characterization,photophysical and electrochemical properties of oxygen bridged twisted heptatomic biphenyl substituted perylene diimides

The perylene diimide derivatives（s-THBPDI and d-THBPDI） bearing oxygen bridged twisty heptatomic biphenyl in the bay positions of the perylene core through acetylene bond were designed and synthesized.The photophysical properties of the functionalized dyes were investigated in solution and solid state by UV-vis and photoluminescence（PL） spectra.Their UV-vis and PL spectrum both exhibited the different concentration-dependent behaviors due to the difference of chemical structure.Moreover,cyclic voltammetry results indicated that the introduction of oxygen bridged twisted heptatomic biphenyl could decrease the LUMO energy level of the perylene diimide effectively and made it promising material in photoelectric devices.

Self-assembly behaviors of the cholesteryl trimeric-phenylene vinylene derivative in the H_2 O/THF system

Cholesteryl trimeric phenylene vinylene （ChoI-TPV） has been synthesized and characterized. The self- assembly behaviors of ChoI-TPV in THF/H20 system at different water content （water content： 40% and 80%） and different solute concentration （solute concentration： 1.0 ×10^-5 mol/L and saturated concentration） were studied using UV-vis spectrophotometry, photoluminescence spectrophotometry, and circular dichroism spectroscopy. Based on an analysis of the UV-vis and photoluminescence spectra, Chol-TPV shows the typical H-type aggregation at saturated concentration in 80% aqueous THF. However, ChoI-TPV shows the non-typical H-type aggregation under other conditions. The circular dichroism signal suggests that the Chol-TPV exists in the right handed helical architectures with high water content at a concentration of 1.0 × 10^-5 mol/L, and a helix inversion was found at saturated concentration.