10 results about "Grain boundary migration" patented technology

This invention belongs to the field of heat exchanger technology, specifically relating to a heat treatment enhancement method and system for heat exchangers. The invention employs a three-stage magnetic field design, applying specific types, parameters, and directions of magnetic fields at three key stages: 200-400℃, 600-900℃, and 900-1100℃. In the low-temperature stage, an alternating magnetic field at a 30-60° angle to the heat transfer path is used to uniformly eliminate residual stress. In the medium-temperature stage, a high-energy pulsed strong magnetic field drives dislocation movement and grain boundary migration. In the high-temperature stage, a uniformly rotating magnetic field achieves uniform distribution of the temperature and electromagnetic fields across the entire domain. This solves the problems of stress concentration, uneven recrystallization, and abnormal grain growth caused by the single direction of the magnetic field in traditional processes. It significantly optimizes the microstructure of the substrate and effectively improves the uniformity of the austenite structure and the grain refinement effect.

The present disclosure provides a method for regulating dynamic recrystallization of NiTi alloy by Ti2Ni phase, comprising: after open-die forging of the as-cast NiTi alloy, performing staged thermal mechanical treatment, first performing first-stage thermal deformation, then performing second-stage thermal deformation, and rapidly water cooling after deformation; by regulating the two-stage variable-temperature and variable-strain rate, Ti2Ni, which is originally considered as a harmful phase, is converted into a micro tool for controlling grain boundary migration; by using Ti2Ni to induce particle-induced nucleation in the low-temperature region, the critical strain required for complete recrystallization is reduced, and the limitation of traditional single thermal coupling driving is broken; this innovative mechanism not only promotes the occurrence of austenite grain dynamic recrystallization process by increasing nucleation sites, but also inhibits the organization coarsening caused by high-temperature grain boundary migration by using the pinning effect of the second phase particles, so as to realize the precise regulation of the uniformity of the organization under a lower deformation amount.

This invention belongs to the field of powder metallurgy technology, and relates to a high-strength and tough multi-scale hierarchical aluminum-based composite material and its powder metallurgy preparation method. The composite material uses aluminum powder, silicon powder, titanium powder, and TiO2 as raw materials. Through a combination of low-temperature powder metallurgy preparation and heat treatment, a multi-scale hierarchical microstructure is generated in situ using solid-state diffusion reactions between the components to produce micron-nano Ti5Si3 particles at grain boundaries and nano-Al2O3 particles within the grains. The preparation method includes: weighing raw materials, graded ball milling and mixing, assembling, degassing and sealing, hot isostatic pressing densification, heat treatment, and machining. This invention achieves stable synthesis of Ti5Si3 and Al2O3 particles through solid-state powder metallurgy; the load-bearing effect of micron-sized Ti5Si3 at grain boundaries and the enhancement of dislocation multiplication and storage capacity by nano-sized Ti5Si3 at grain boundaries and nano-Al2O3 within the grains hinder grain boundary migration and dislocation movement under room temperature / high temperature conditions, synergistically improving the room temperature strength, toughness, and high-temperature performance of the composite material.

This invention relates to a machine learning potential function construction method for Mg-Al-Ca and Mg-Al-Zn magnesium alloy systems. The method includes: constructing an atomic-level initial configuration dataset covering solid solutions, dislocations, grain boundaries, stacking faults, twins, precipitates, and free surfaces; performing first-principles calculations to obtain energy, atomic forces, and stress tensors; converting the data format; training a machine learning potential function model using a deep potential energy method; and verifying the accuracy to a root mean square error of less than 5 × 10⁻⁶. ‑ ²eV / atom, root mean square error of force less than 1×10 ‑ ¹eV / Å. The potential function constructed in this invention combines first-principles accuracy with molecular dynamics efficiency, accurately describing the interatomic interactions of complex defects and precipitates. It can be used to study microscopic mechanisms such as solute segregation and grain boundary migration, providing computational tools for magnesium alloy composition design and process optimization.

This invention provides a refining-strengthening agent, its preparation method, and its application, belonging to the field of aluminum alloy technology. The refining-strengthening agent provided by this invention comprises the following components by mass percentage: 5-15% nano-ceramic particles, 1-3% rare earth elements, 1-3% Zr, and the balance Al; the nano-ceramic particles include ZrB2, TiB2, and Al2O3. In this invention, the nano-ceramic particles ZrB2, Al2O3, and TiB2 can act as heterogeneous nucleation cores for α-Al within aluminum grains, pinning grain boundaries and hindering grain boundary migration. During deformation, they also impede dislocation movement, simultaneously forming fine recrystallized grains, thereby improving the refining and strengthening effects. The addition of rare earth elements enables the nanoparticles to achieve both refining and strengthening effects. The combination of Zr and rare earth elements provides excellent anti-coarsening properties, thus enabling the refining-strengthening agent to exhibit good strengthening effects at both high and room temperatures.

This invention discloses an efficient magnetic domain refinement method for ultra-low loss oriented silicon steel, relating to the field of steel material technology. The method includes: raw material preparation; hot rolling and final rolling; multi-stage thermomechanical processing; controlled suppression phase formation; secondary re-junction and magnetic field-induced selective growth; surface microstructure fabrication; low-temperature domain refinement annealing and alternating magnetic field coupling; segmented cooling and quality inspection. This invention, through controlled nanoscale suppression phase engineering, forms a high-density and uniform nanoscale suppression phase within the matrix, serving as pinning sites for grain boundaries and subgrain boundaries. This controls grain boundary migration dynamics during high-temperature secondary re-junction, overcoming the problems of abnormal grain growth and microstructure instability caused by uneven distribution and large size dispersion of traditional suppression phases. This avoids the root cause of large magnetic domains, improves the controllability and repeatability of the secondary re-junction process, obtains a more uniform orientation grain size distribution, and reduces localized magnetic domain enlargement and iron loss fluctuations caused by uneven grain size.

The application discloses a preparation method for improving the strength performance of 7xxx series aluminum alloy and belongs to the technical field of aluminum alloy material preparation. The application uses homogenization treatment + fast cooling cycle to make Zn, Mg, Cu and Cr micro-alloying elements uniformly distributed in the alloy, and CrAl7 intermetallic compound is generated in the microstructure and has a pinning effect, so that the grain boundary migration is difficult, and the recrystallized grains hinder the nucleation and growth of recrystallization. Then, a medium average strain rate and a proper hot rolling temperature are selected for rolling to obtain an organization structure in which the coarse grains are embedded in the fine grains. Finally, the material performance is further improved through pre-deformation and regression re-aging heat treatment. Through the synergistic effect of micro-alloying, homogenization treatment + fast cooling treatment, hot rolling treatment, pre-deformation and regression re-aging heat treatment, the proportion of the organization structure in which the coarse grains are embedded in the fine grains is improved, so that the strength and corrosion resistance of the 7xxx series aluminum alloy are improved.

This invention discloses an ultrafine-grained cemented carbide cutting tool material and its preparation method, belonging to the field of powder metallurgy technology. Addressing the technical contradictions in existing technologies where liquid-phase sintering densification inevitably leads to grain coarsening, and the addition of grain growth inhibitors results in decreased toughness, this invention employs a time-differentiated confined liquid-phase sintering strategy combined with in-situ vanadium element interface control. A vanadium-containing coating layer is formed on the surface of WC powder through precursor conversion. After pressing, a pre-sintering process is performed at 1280℃ to 1300℃ for 30 to 60 minutes to form a confined liquid phase, achieving a relative density of over 95% and grain size less than 0.25 micrometers. A final sintering process is then performed at 1350℃ to 1400℃ for 10 to 30 minutes to complete full densification. The solute dragging effect of vanadium grain boundary segregation is utilized to suppress grain boundary migration. Without adding external inhibitors, an ultrafine-grained cemented carbide with an average grain size of less than 0.3 micrometers and a fracture toughness greater than 15 MPa square kJ is obtained, suitable for high-speed cutting of titanium alloys and nickel-based high-temperature alloys.

The application provides a crystal plasticity-cellular automaton coupling multiscale framework for simulating dynamic recrystallization behavior of nickel-based superalloy, which is used for accurately predicting microstructure-mechanical coupling evolution of dynamic recrystallization of the nickel-based superalloy, and overcomes the fundamental incompatibility between the state transition of CA mutation and the continuous field variable of CPFE by introducing a continuous transformation fraction, and steps include: based on experimental data and statistical analysis, establishing a representative volume element (RVE), at each increment step k, solving a balanced mechanical field according to a boundary condition in a CPFE module, mapping key variables to a CA module, updating recrystallization cell state variables and feeding back to the CPFE module after nucleation and grain boundary migration judgment in the CA module, and iterating until the deformation is finished. The framework can accurately predict grain structure evolution, stress-strain response, dislocation density and texture evolution, and is suitable for nickel-based superalloy, titanium alloy and the like, and provides support for microstructure design and performance control of metal hot working.

This invention discloses a carbon-coated Li5AlO4, its preparation method, and its applications, belonging to the field of lithium supplementation technology. The preparation method includes the following steps: S1: mechanically mixing a lithium source, an aluminum source, and a carbon source to obtain a mixture; heat-treating the mixture under an inert atmosphere to obtain a precursor; S2: mechanically mixing the precursor and the carbon source to obtain a carbon-coated Li5AlO4 under an inert atmosphere. The carbon source introduced in the Li5AlO4 synthesis stage of this invention effectively suppresses particle coarsening during crystal sintering; while in the precursor carbon coating process, the presence of the carbon source hinders grain boundary migration and particle agglomeration during high-temperature treatment. The synergistic effect of these dual carbon regulation mechanisms allows this invention to directly obtain small-particle, uniformly carbon-coated Li5AlO4 products without relying on post-processing techniques such as ball milling or airflow crushing.