In this study, TiB + La2O3/Ti-6Al-4V composites were successfully prepared by in situ reaction using selective laser melting technology. The effect of LaB6 content on the fabrication quality, microstructure evolution and mechanical properties of the composite samples was investigated. The results show that the relative density of the sample gradually decreased from 98.56% to 96.57% as LaB6 content increased from 0 wt% to 3 wt%. With increasing LaB6 content, TiB precipitates gradually aggregated and grew from a discrete needle-like structure to a dendritic structure, before eventually developing a cell-like structure. The dislocations piled up around the TiB and La2O3 reinforcements, which impeded the motion of the dislocations and led to the enhancement of the tensile strength of the samples. Different from the addition of a single reinforcement due to the combined strengthening effect of the micrometer-scale and nanoscale reinforcements, the strength of the samples was increased significantly. The Ti-6Al-4V sample with 3 wt% LaB6 addition showed the most significant strengthening effect. Compared to the pure Ti-6Al-4V sample, the 3 wt% LaB6 addition sample gained a 35.71% increase in hardness and a 14.5% increase in tensile strength. Additionally, wear volume was reduced by 47.5%. The results revealed that the addition of LaB6 was a potential way to improve the mechanical performance of the titanium alloys in the additive manufacturing process.

e roof steel structure in the Terminal 2 building of YanCheng NanYang Airport has a large span and a considerably difficult construction. According to the project characteristics, the construction scheme of the roof steel structure follows the principle of subareas and substeps, with the truss lifting in segmentation. To ensure construction safety, a construction monitoring scheme was adopted in this project. According to the layout of the roof steel structure, a total of 10 monitoring points are arranged to monitor the stress of the roof steel structure during the construction process. is paper first gives a brief introduction to the general situation regarding the engineering, followed by a detailed description of the construction scheme of such a roof steel structure. en, the monitoring results, including monitoring of the main truss' stress and column head, are introduced. e monitoring results revealed that the variation of stress in monitoring points followed the same trend as the monitoring data. e maximum stress was 166.6 MPa according to the monitoring results, which indicate that the stress of the roof steel structure is in the elastic stage during the construction process and the construction scheme is feasible.

No abstract

Iron is an important metal material that supports the development of society and national economies. Due to the uneven distribution of resources, there is frequent trade around the world. Therefore, mastering the global flow path and trade pattern provides an essential basis for the sustainable utilization of iron and related products. Based on the artificial flow of iron in international trade, this study used the material flow analysis method to investigate this flow. Based on the data of China’s international iron trade from China Customs and the United Nations trade administration, this study systematically analyzed the structure, type, quantity, and value of iron-containing commodities in 2018. The results were as follows: (1) China was a net importer of iron and formed a trade structure of “import raw materials and export products.” (2) There was a large trade surplus in China’s iron international trade. The quality of iron exported by China was high, and the price is relatively low; therefore, countries around the world have a great dependence on the iron imported from China. (3) Compared with developed countries, China is in urgent need of high-end technologies and can only import high-tech iron products from abroad. Therefore, the value of China’s exports of iron-containing commodities is relatively low, while that of its imports is relatively high.

is paper presents the results of a numerical and analytical study to investigate the effect of adhesive interface on the ultimate capacity of a new composite sandwich shear wall: double-superposed shear wall. e effect of adhesive interface on the ultimate capacity of two different wall configurations under different axial compression ratios was studied. e results indicate that, for the two different wall configurations, the bond strength of adhesive interface has a negligible effect on ultimate bearing capacity. As a result of the different intensity grades between cast-in-situ concrete wythe and precast concrete wythe, the double-superposed shear wall with precast boundary elements (wall configuration W3) yields a higher ultimate bearing capacity than that with castin-place boundary elements (wall configuration W2), when the axial compression ratio exceeds 0.2, which is contrary to the results under 0.1 axial compression ratio. A new calculation method for ultimate bearing capacity is proposed to take into account the different intensity grades, and the calculation results show a very good agreement with the numerical simulation results.