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In the present study, the densification behavior, microstructural evolution, mechanical properties, and friction behavior of a TiB2/Al8SiCu composite and Al8SiCu alloy manufactured by laser powder-bed fusion (PBF-LB) were systematically investigated. The results confirm that the addition of in situ TiB2 particles into Al8SiCu alloys reduce the volumetric energy density required for a high-density TiB2/Al8SiCu composite. The TiB2 particles promoted a transformation of columnar to equiaxed crystals and the formation of high-angle grain boundaries. The grains on the vertical direction of the PBF-LBed TiB2/Al8SiCu composite were much finer than those of the PBF-LBed Al8SiCu alloy. The addition of TiB2 promoted the grain refinement of the Al8SiCu alloy, of which the average grain size decreased from 15.31 μm to 7.34 μm. The yield strength (YS), ultimate tensile strength (UTS), and elongation (El) of the PBF-LBed Al8SiCu alloy were 296 ± 6 MPa, 517 ± 6 MPa, and 11.7 ± 1.0%, respectively. The PBF-LBed TiB2/Al8SiCu composite achieved a balance between strength and ductility with a yield strength of 328 ± 8 MPa, an ultimate tensile strength of 541 ± 3 MPa, and an elongation of 9.1 ± 0.7%. The increase in strength mainly resulted from grain boundary strengthening, dislocation strengthening, load-bearing strengthening, solid-solution strengthening, and Orowan strengthening, of which the dislocation strengthening and Orowan strengthening were critical. The enhanced hardness associated with the grain refinement and the formation of the in situ TiB2 particles also led to an enhanced tribological performance, of which reductions in the average friction coefficient from 0.655 to 0.580 and wear rate from 1.76 × 10−3 mm3/Nm to 1.38 × 10−3 mm3/Nm were found. [ABSTRACT FROM AUTHOR]

Purpose: The incorporation of ryegrass (Lolium multiflorum Lam.; RG), a winter manure, could partly replace chemical N and reduce N loss during the succeeding rice seasons, but little is known about its impact on greenhouse gas emission. This study investigated the effect of different RG-urea substitution ratios (0% RG and 100% urea, 25% RG and 75% urea, 50% RG and 50% urea, 75% RG and 25% urea, 100% RG and 0% urea,) on net C and N mineralization, CH4 and N2O emissions in a paddy soil. Methods: Gas samples for CH4 and N2O fluxes were collected by using a closed chamber and determined by chromatograph method. Net C and N mineralization from the incorporated RG residue were tested by a mesh bag method. Results: Net C and N mineralization from RG followed a single exponential decay model, with 95.5%-97.8% of the original C and 98.7%-99.3% of N released during 192 days. The RG-urea substitution ratio increased CH4 emission, but was negatively correlated with N2O emission. In comparison with 0% substitution, global warming potential (GWP) and greenhouse gas intensity (GHGI) were not significantly different for the 25% and 50% RG substitutions, but were significantly higher for the 75% and 100% substitutions (P < 0.05). Soil redox, C and N remaining in litter residue were key characteristics explaining CH4 emission, while NH4+-N and NO3−-N were correlated with N2O emission. Conclusion: The increased GWP by CH4 emission after RG incorporation could be offset by N2O reduction when RG-urea substitution ratio was 50% or less. [ABSTRACT FROM AUTHOR]