A rapid aging treatment method of Al-7Si-0.55Mg alloy using electric pulse, namely electric pulse aging treatment, is explored in this study. The effect of electric pulse assisted aging on microstructure and properties of Al-7Si-0.55Mg alloy are investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), tensile tests and hardness tests. The results show that the microstructure of the Al-7Si-0.55Mg alloy is effectively refined, and the morphology of eutectic Si changes from long and thin strip to a spherical shape or short rod. The elongation of the Al-7Si-0.55Mg alloy is significantly improved after electric pulse assisted aging, albeit it did slightly compromise the tensile strength. It is important to reduce the aging time by 3 h, saving energy. According to classical nucleation theory, the formula of the phase nucleation rate promoted by an electric pulse was determined. The application of an electric pulse can accelerate the nucleation of phase transformation by decreasing the thermodynamic energy barrier, which increases the nucleation rate and significantly improves the properties of the alloy. It provides an experimental and theoretical basis for the Al-7Si-0.55Mg alloy to obtain good mechanical properties and industrial applications.

Shrinkage greatly influences the mechanical and fatigue properties of compacted graphite iron and it is necessary in order to study the causes of shrinkage in compacted graphite iron and to predict it effectively. In this paper, a kind of cylindrical necking test sample was designed to evaluate the shrinkage in compacted graphite iron, and a method to calculate the size of shrinkage was proposed. By observing the microstructure around the shrinkage zone, it is concluded that concentrated shrinkage mainly appears in the solidification region where the dendritic gap is closed, and the isolated shrinkage mainly occurs in the final solidification region, and the supersaturated carbon elements are gathered on the surface of the shrinkage. The cause of shrinkage in compacted graphite iron is caused by its solidification method, where the austenite dendrites and the eutectic clusters are generated close to the melt zone during the solidification process, leading to the inability to feed the shrinkage. Based on the thermodynamic analysis, the equations between the volume change of each phase, solid phase rate, and time during solidification of compacted graphite iron were established to theoretically explain the formation mechanism of the shrinkage. Taking nine parameters such as the chemical elements and characteristic values of thermal analysis as the input nods, a four-layer BP neural network model for predicting the size of shrinkage in compacted graphite iron was constructed, and the R-squared of the model reached 97%, which indicates it could be used to predict the shrinkage tendency.

The effects of electro-pulse on microstructure and mechanical properties of Al-Cu-Mn-Zr-V alloy were investigated, and the ageing mechanism was analyzed. As the current density increases, the size and quantity of precipitates gradually transit from continuous aggregation to dispersion at grain boundaries, and the mechanical properties are improved. When the current density is 15 A·mm⁻², the precipitates are smallest and the mechanical properties are best. The tensile strength is 443.5 MPa and the elongation is 8.1%, which are 51.7% and 42.1% higher than those of conventional ageing treatment, respectively. Once the current density exceeds 15 A·mm⁻², the precipitates will increase again and gather at grain boundaries, and the mechanical properties also decrease. An additional electrical free energy arising from an electro-pulse provides thermodynamic and kinetic conditions for the ageing precipitation of second phases. The electro-pulse can enhance the ageing diffusion coefficient, being improved by 34 times for 15 A·mm⁻². The electro-pulse improves the nucleation rate and decreases the critical nucleation radii of second phases. However, it also accelerates the grain growth, making the second phases become coarse. An electro-pulse with a current density of 15 A·mm⁻² can rapidly nucleate the second phase at 463 K while the precipitates are relatively small after growth.

To address high-precision robotic abrasive belt grinding of 42CrMo steel, this study adopted the orthogonal central composite design with grinding force, feed rate, and rotational speed as key parameters, establishing and verifying regression models for material removal depth (MRD) and surface roughness (Ra). Results showed that the models’ relative errors are within 6% (MRD) and 10% (Ra). Grinding force and feed rate exert a strong coupling effect on MRD, while feed rate–rotational speed and grinding force–feed rate interactions significantly influence Ra, with “saddle-shaped” response surfaces. Grey relational analysis determined the optimal parameters: 75 N grinding force, 22.4 mm·s⁻¹ feed rate, and 3261 rpm rotational speed, achieving a maximum MRD of 1.975 mm and a minimum Ra of 3.506 μm. The tolerance range of the optimal parameters is F = 70–80 N, v_f = 20–24 mm·s⁻¹, and ω = 3000–3500 rpm. This research provides robust support for process parameter prediction and optimization in high-precision robotic abrasive belt grinding of 42CrMo steel.

The moisture of green sand mainly refers to the water that can be got rid of at the temperature of 105℃-110℃, and it is affecting sand quality, one of the most important and sensitive parameters that affect the quality of green sand. At present, the methods for measuring the moisture content can be divided into two categories of direct and indirect methods. The precision of the direct method is high while the measurement period is long, so it does not suits to online measurement, and is often used to calibrate the indirect methods. In the indirect methods, the moisture content can be online obtained by measuring the physical parameters or performance indexes related to the moisture. They mainly include the resistance method, capacitance method, inductive method, microwave method, infrared spectrometry method, and nuclear magnetic resonance method.