Aiming at the question of improvement expansive soil in Nanyang area, the composite improvement method of lignin and cement was adopted. Based on the unconfined compressive strength test, the variation law of unconfined compressive strength of improved expansive soil with different lignin content, different compaction degree and different curing age was studied. The test results show that the composite of lignin and cement can effectively improve the unconfined compressive strength of expansive soil. The unconfined compressive strength of L-C (lignin and cement) improved expansive soil reaches the maximum when the cement content is fixed at 4% and the lignin content is 1%. The unconfined compressive strength of L-C improved soil increases with the increase of compaction degree and curing age, and the strength growth mainly concentrated in the first 7 days of curing age. From the point of improvement mechanism, the hydration and gelation reaction of cement occur in expansive soil, and gel material with higher strength is formed to enhance the strength of expansive soil. The appropriate amount of lignin can fill the pores between soil particles and make the connection between soil particles more closely, so as to improve the strength of expansive soil.
As a high‐efficiency laser additive manufacturing technology, laser powder bed fusion (LPBF) has unparalleled advantages in the manufacture of titanium matrix composites. In this work, the effect of laser energy density (LED) on the forming quality, microstructure evolution, and corrosion resistance of LPBF‐fabricated nanographene oxide reinforced titanium matrix nanocomposites (GO/TC4) was investigated. The results show that the optimal surface roughness and relative density of GO/TC4 nanocomposites fabricated by LPBF are 11.8 μm and 99.40%, respectively. The microstructure is mainly acicular α/α′‐Ti, accompanied by a small amount of β‐phase grain boundaries. When the LED is increased to 58.33 J/mm3, the self‐corrosion potential of GO/TC4 sample reaches 0.345 V in 3.5 wt% NaCl solution, and the GO/TC458.33 nanocomposite exhibits the highest corrosion resistance. The results revealed that the corrosion products on the surface of the samples were mainly composed of a passivation film of TiO2 and a small amount of Al2O3.
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