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Effect of Co element on the microstructure and mechanical properties of maraging steel is studied and summarized. The microstructure and mechanical properties of five different compositions of maraging steels were characterized and tested in three heat treatment states, with the heat treatment schemes of homogenization treatment at 1300 °C × 10h, solution treatment at 800 °C × 2h, and aging treatment at 480 °C × 5h. The research has discovered that increasing the Co content in three different heat treatment states can lead to a reduction in the size of the original austenite grains and the width of martensite laths. In the aged state, higher Co content causes the precipitation phase to transform from an ellipsoidal Mo-rich phase to a needle-like Ni3(Mo, Ti) phase. These changes in the size, shape, and density of the precipitated phases result in a more pronounced effect of precipitation strengthening, leading to a significant increase in the material's strength.

This article is aimed at finding the feasible measures to reduce the early plastic crack of cement concrete, by means of field test and simulating test from laboratory. This essay discusses the advantages and disadvantages of various conservation measures (Including spray all kinds of curing agent; Coverage; Early spray; Secondary cement-plastering), Distinguishes effective control measures. According to the test results this paper puts forward effective construction method and construction material of timely maintenance of new concrete, provides reference ideas for the future engineering construction.