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The casting simulation software ProCAST was used to achieve the simulation of the filling and solidification process of the high Nb-TiAl alloy impeller investment casting. The influence of the casting and filling process on the filling and solidification characteristics of alloy melt filling, shrinkage cavity and porosity was studied, and the corresponding process was optimized. The casting test and the non-destructive testing analysis of the casting were carried out, and the anatomical analysis of the casting was performed to verify the distribution of the shrinkage cavity and porosity. The mechanical properties of the impeller at room temperature and high temperature were studied using attached test rods. The results show that ProCAST software is more accurate in predicting shrinkage cavity and porosity of the high Nb-TiAl casting, and the process scheme is optimized by simulation and prediction results to avoid the formation of large shrinkage cavity and porosity in casting, only micro shrinkage cavity less than 22 μm is existed in the final casting. All castings are fully filled, with the tensile strength about 580 MPa at room temperature and about 450 MPa at high temperature of 850 ℃.

In the high-speed railways equipped with CTCS-2 train control system, the cab signals serve as the running token, and affect train braking curve generation and over-speed protection, thus providing important guarantee for high-speed train operation. This paper analyzes several typical code missing cases of the cab signal system, and studies the software logic processing process of the onboard equipment. On this basis, it summarizes the on-site operation situation of typical fault cases and proposes the corresponding treatment measures. [ABSTRACT FROM AUTHOR]

Hybrid manufacturing of titanium alloys by investment casting and laser additive manufacturing (LAM) combines the advantages of both techniques and can further reduce the cost. In this study, microstructure evolution in the bonding zone and tensile property of the hybrid manufacturing Ti-6Al-4V alloy are carefully investigated. Results show that the hybrid sample consists of the LAM zone, the heat-affected zone (HAZ) and the base casting zone. A transition zone (TZ) forms within the HAZ close to the fusion line. Grains in the bottom of the LAM zone are much finer with a mixture of equiaxed grain and small columnar grain, and gradually coarsening to fully large columnar grains. Typical ultra-fine basket-wave microstructure forms in the LAM zone. In the TZ, the microstructure gradually changes from a fine basket-wave microstructure to a coarsened bimodal microstructure. The highest microhardness of the bonding zone is 491 HV. The fracture of the hybrid sample occurs in the casting half, and the tensile strength of the hybrid sample reaches (821 ± 31) MPa, which is higher than that of the pure casting sample ((778 ± 22) MPa). However, the elongation of the hybrid sample ((8.0 ± 0.5)%) is lower than that of the pure casting sample ((10.0 ± 1.7)%). [ABSTRACT FROM AUTHOR]

For a 230t large steel ingot which is firstly manufactured in one industrial plant, both of the analytical calculation and the numerical simulation methods were adopted to predict the total solidification time based on their own physical and mathematical models. The results showed that the total solidification time calculated by the analytical method was 46.0 h, and that was 40.2 h by the numerical method. Comparing with the actual stripping time of 45.8 h for the 230t large steel ingot, both of the estimated values agreed reasonably well with the actual one. For the purpose of practical utilization, the analytical method tends to be more convenient rather than the numerical one. This study can provide a kind of reference for the prediction on the total solidification time of large steel ingots. [ABSTRACT FROM AUTHOR]