Preparation of high strength and electrical conductivity copper-chromium pseudobinary alloy by cold-rolling of a billet produced by laser additive manufacturing

A new method to prepare large Cu–Cr alloy with both high strength and high conductivity has been developed. Cu–Cr billets are produced efficiently by laser additive manufacturing, and the microstructure of the alloy is changed by severe plastic deformation caused by large cold rolling ratio. The strength of the alloy can be significantly increased to 677 MPa by eliminating pores, introducing texture and refining grain. The deformation twins caused by plastic deformation processing make up for the plasticity loss caused by grain refinement. With the increase of density and the deformation of Cr particles, the electrical conductivity of the alloy is increased to 28.7 MS/m. Our findings not only deepen the understanding of laser additive manufacturing of highly reflective metals, but also provide a new idea for the preparation of high-strength and high-conductivity Cu alloy workpieces

Build an Integrated Scene Teaching System for Additive Manufacturing Based on the Integration of Production and Education

Additive manufacturing, also known as 3D printing, is known as one of the subversive intelligent manufacturing technologies that can lead industrial transformation. It has significant advantages in personalized customization and preparation of complex structural components, and is having an important impact on traditional manufacturing process, factory production and processing mode and the entire manufacturing industry chain. At present, the talent gap of additive manufacturing and related specialties in China exceeds 10 million, of which the manufacturing industry has the largest demand for additive manufacturing application talents. It is estimated that the talent gap will be 8 million by 2025. The construction of scenario based teaching system of additive manufacturing integrated courses based on the integration of production and education. At present, it is urgent for universities and vocational education to fully integrate the “research” and “technology” of universities and vocational education institutions with the “production” of enterprises to build a scenario of production and education integration education that suits students. By creating real and vivid scenes for students, Help students get familiar with the background and business operation process of the integrated operation of additive manufacturing, strengthen students’ ability to integrate theoretical knowledge, and apply what they have learned in combination with practice

Structural and magnetic characterization of Al microalloying nanocrystalline FeSiBNbCu alloys

The magnetic properties of nanocrystalline Fe77Si10B9Cu1Nb3-xAlx (x = 0 and 1) alloys have been investigated and their structural and electromagnetic parameters have been quantitatively studied by X-ray diffraction, transmission electron microscopy and Mossbauer spectra under one-step and two-step annealing processes. The nanocrystalline structure consists of single alpha-Fe(Si) phase embedded in a residual amorphous phase. Both saturation magnetic flux density (B-s) and permeability (mu) of the nanocrystalline alloys are increased by substituting 1 at% Al for Nb and one-step annealing, from B-s= 1.41 T to 1.47 T and from mu = 18,000 to 23,000 at 1 kHz, respectively. The two-step annealing has little effect on the B-s, coercivity (H-c) and grain size of the nanocrystalline alloys, but greatly improves the mu of the Al-doped alloy, reaching up to 28,000 at 1 kHz. The improved mu can be attributed to the increased magnetic moment and exchange stiffness constant, homogeneous chemical structure and reduced magnetostriction. The Al-doped nanocrystalline alloy with high B-s, high mu, low H-c and good frequency stability are good candidates for magnetic shielding pieces of wireless charging

Resolving aging dynamics of a 3D colloidal glass

Physical aging is an inherent property of glassy matter, but understanding its microscopic mechanism remains a challenge particularly at the particle level. In this work, we use a confocal microscope to in-situ trace the particle trajectories in a 3D colloidal glass for 73000 s, aiming at resolving the aging dynamics. By calculating the mean square displacement of particle motions, we find that the glass aging with time can be divided into three stages: beta relaxation, alpha relaxation and free diffusion. The system's mean square displacement at each aging state is quantitatively resolved into three contributions of particle dynamics modes: vibration within the nearest-neighbor cages, hopping between cages and cooperative rearrangement. We further calculate the particle's free volume and find that the beta-to-alpha transition is accompanied by the temporary increase of the system-averaged free volume due to pronounced hops of particles. Nevertheless, the temporal autocorrelation of the free volume spatial distribution still obeys a monotonically stretched exponential decay with an exponent of 0.76, which is related to the sub-diffusion dynamics of cooperative rearrangements and hops mixed in alpha relaxation. According to the resolved vibrational displacements, we calculate the vibrational density of states of this 3D glass, and the characteristic boson peak is reproduced at low frequencies. Our findings shed insight into the particle-level aging dynamics of a real glass under purely thermal activation

Roles of interface engineering in performance optimization of skutterudite‐based thermoelectric materials

Abstract Interface engineering has prevailed in the thermoelectric field for decades, and related performance has achieved great progress. Therefore, an in‐depth understanding of the impacts of the interface effect on the thermoelectric transport parameters is of vital importance. In this paper, taking skutterudite‐based thermoelectric materials as typical examples, the formation mechanism and preparation process of various interface types, including 1D dislocations, 2D grain refinement, 3D nanocomposites, and micro‐nanopores, are briefly summarized. In addition, we also systemically highlight recently striking achievements related to interfacial design to reveal the distinctive effect of each interface structure on the transport behavior of carriers and phonons. Finally, existing challenges in the thermoelectric performance optimization achieved by interface engineering are pointed out, and an outlook for further thermoelectric research is presented

A Comparative Study on the K-ion Storage Behavior of Commercial Carbons

Potassium-ion battery, a key analog of lithium-ion battery, is attracting enormous attentions owing to the abundant reserves and low cost of potassium salts, and the electrochemically reversible insertion/extraction of the K-ion within the commercial graphite inspires a research spotlight in searching and designing suitable carbon electrode materials. Herein, five commercially available carbons are selected as the anode material, and the K-ion storage capability is comparably evaluated from various aspects, including reversible capacity, cyclability, coulombic efficiency, and rate capability. This work may boost the development of potassium-ion batteries from a viewpoint of practical applications