The effect of the Mg/Si ratio of Al-2.5Li-1Cu-0.8Mg-0.8Si,Al-2.5Li-1Cu-1.6Mg-0.8Si,and Al-2.5Li-1Cu-2.4Mg-0.8Si alloys on the microstructure evolution and mechanical properties was investigated.The results show that t...The effect of the Mg/Si ratio of Al-2.5Li-1Cu-0.8Mg-0.8Si,Al-2.5Li-1Cu-1.6Mg-0.8Si,and Al-2.5Li-1Cu-2.4Mg-0.8Si alloys on the microstructure evolution and mechanical properties was investigated.The results show that the primary phases and their morphologies in the as-cast alloys are found to vary with the Mg/Si ratio.The improvement of Mg/Si ratio of as-cast alloys promotes the formation of Mg_(2)Si primary phase at the expense of the AlLiSi primary phase.Moreover,a tiny amount of T_(B)-Al_(7.5)Cu_(4)Li phase transforms into S-Al_(2)CuMg phase with the increase of Mg content.In addition,the increase of Mg/Si ratio also causes the Cu-rich intergranular phase distributed along crystal boundary to Si-rich intergranular phase.After ageing treatment,the precipitation sequence as a function of Mg/Si ratio is as follows:δ/δ'+AlLiSi(Mg/Si is~1)→δ/δ'+β'-Mg_(2)Si+AlLiSi(Mg/Si is~2)→δ/δ'+β'-Mg_(2)Si(Mg/Si is~3).A good combination of strength and ductility can be obtained in Al-2.5Li-1Cu-2.4Mg-0.8Si alloy after solution and ageing.The rod-likeβ'-Mg_(2)Si precipitate has a positive influence on the comprehensive mechanical properties of the alloy.展开更多
The effect of adding 0.03wt%Ni on the microstructure and mechanical properties of Al–Mg–Si–Cu–Zn alloys was systematically studied.The results reveal that the number density of spherical Fe-rich phases within grai...The effect of adding 0.03wt%Ni on the microstructure and mechanical properties of Al–Mg–Si–Cu–Zn alloys was systematically studied.The results reveal that the number density of spherical Fe-rich phases within grains increases with the addition of Ni,accompanied by the formation of Q(Al3Mg9Si7Cu2)precipitates around the spherical Fe-rich phases.Additionally,Ni addition is beneficial to reducing the grain size in the as-cast state.During the homogenization process,Q phases could be completely dissolved and the grain size could remain basically unchanged.However,compared with the Ni-free alloy,the Fe-rich phase in the Ni-containing alloy is more likely to undergo the phase transformation and further form more spherical particles during homogenization treatment.After thermomechanical processing,the distribution of Fe-rich phases in the Ni-containing alloy was further greatly improved and directly resulted in a greater formability than that of the Ni-free alloy.Accordingly,a reasonable Ni addition positively affected the microstructure and formability of the alloys.展开更多
This study is a contribution to improving rice productivity on acidic plateau soils of the tropical rainforest zone. It is based on taking into account the cationic balances of the soil in order to optimize the phosph...This study is a contribution to improving rice productivity on acidic plateau soils of the tropical rainforest zone. It is based on taking into account the cationic balances of the soil in order to optimize the phosphorus (P) nutrition of rice on these acidic soils, where this nutrient constitutes a limiting factor for agricultural production. Three (3) pot trials were conducted in Adiopodoumé in the forested south of Côte d’Ivoire. The interactive effects of calcium carbonate (0, 25, 50 and 75 kg Ca ha<sup>−1</sup>) and magnesium sulfate (0, 25, 50 and 75 kg Mg ha<sup>−1</sup>) were evaluated on the response of NERICA 5 rice at doses 0, 25, 50 and 75 kg P ha<sup>−1</sup> of natural phosphate from Togo, applied only once at the start of the experiment. Additional fertilizers of nitrogen (N) (100 kg N ha<sup>−1</sup>) and potassium (K) (50 kg KCl ha<sup>−1</sup>) were added to each of the tests in a split-plot device. The test results revealed a paddy production potential of approximately 3 to 5 t⋅ha<sup>−1</sup> for NERICA 5 on an acidic soil, under the effect of the interaction of P, Ca and Mg. The quadratic response of rice yield to the doses of these fertilizers would be more dependent on their balance, itself influenced by Ca nutrition. For the sustainability and maintenance of rice production in agro-ecology studied, it was recommended doses of 38 kg Ca ha<sup>−1</sup>, 34 kg Mg ha<sup>−1</sup> in a Ca/Mg ratio (1/1) with intakes of 41 kg P ha<sup>−1</sup>, overall in a ratio 1/1/1 (P/Ca/Mg) more favorable to the availability of free iron considered a guiding element of mineral nutrition. Thus, these promising results should be confirmed in a real environment for better management of the fertilization of rice cultivated on acidic plateau soils in Côte d’Ivoire.展开更多
Al-Mg-Si-Sc alloys with different Mg/Si ratio(<1.73 in wt.% vs>1.73 in wt.%) and different grain size(coarse grains vs ultrafine grains) were prepared, which allowed to investigate the grain size-dependent Mg/Si...Al-Mg-Si-Sc alloys with different Mg/Si ratio(<1.73 in wt.% vs>1.73 in wt.%) and different grain size(coarse grains vs ultrafine grains) were prepared, which allowed to investigate the grain size-dependent Mg/Si ratio effect on the microstructural evolution and concomitantly on the hardness and electrical conductivity when subjected to aging at 200℃. In the coarse-grained Al-Mg-Sc-Sc alloys, the β" precipitation within the grain interior and also the precipitation hardening were highly dependent on the Mg/Si ratio,while the electrical conductivity was slightly affected by the Mg/Si ratio. A promoted β" precipitation was found in the case of Si excess(Mg/Si ratio <1.73), much greater than in the case of Mg excess(Mg/Si ratio>1.73). While in the ultrafine-grained Al-Mg-Si-Sc alloys, the electrical conductivity rather than the hardness was more sensitive to the Mg/Si ratio. The alloy with Si excess displayed electrical conductivity much higher than its counterpart with Mg excess. This is rationalized by the grain boundary precipitation promoted by Si, which reduced the solute atoms and precipitates within the grain interior. Age softening was found in the ultrafine-grained alloy with Si excess, but the ultrafine-grained alloy with Mg excess held the hardness almost unchanged during the aging. The hardness-conductivity correlation is comprehensively discussed by considering the coupling effect of Mg/Si ratio and grain size. A strategy to simultaneously increase the hardness/strength and electrical conductivity is proposed for the Al-Mg-SiSc alloys, based on present understanding of the predominant factors on strengthening and conductivity,respectively.展开更多
基金financially supported by the National Natural Science Foundation of China(51774105)Touyan Innovation Team Program(XNAUEA5640208420)。
文摘The effect of the Mg/Si ratio of Al-2.5Li-1Cu-0.8Mg-0.8Si,Al-2.5Li-1Cu-1.6Mg-0.8Si,and Al-2.5Li-1Cu-2.4Mg-0.8Si alloys on the microstructure evolution and mechanical properties was investigated.The results show that the primary phases and their morphologies in the as-cast alloys are found to vary with the Mg/Si ratio.The improvement of Mg/Si ratio of as-cast alloys promotes the formation of Mg_(2)Si primary phase at the expense of the AlLiSi primary phase.Moreover,a tiny amount of T_(B)-Al_(7.5)Cu_(4)Li phase transforms into S-Al_(2)CuMg phase with the increase of Mg content.In addition,the increase of Mg/Si ratio also causes the Cu-rich intergranular phase distributed along crystal boundary to Si-rich intergranular phase.After ageing treatment,the precipitation sequence as a function of Mg/Si ratio is as follows:δ/δ'+AlLiSi(Mg/Si is~1)→δ/δ'+β'-Mg_(2)Si+AlLiSi(Mg/Si is~2)→δ/δ'+β'-Mg_(2)Si(Mg/Si is~3).A good combination of strength and ductility can be obtained in Al-2.5Li-1Cu-2.4Mg-0.8Si alloy after solution and ageing.The rod-likeβ'-Mg_(2)Si precipitate has a positive influence on the comprehensive mechanical properties of the alloy.
基金financially supported by the National Key Research and Development Program of China(No.2016YFB0300801)the National Natural Science Foundation of China(Nos.51871029,51571023,and 51301016)+2 种基金Beijing Natural Science Foundation(No.2172038)Beijing Laboratory of Metallic Materials and Processing for Modern Transportation(No.FRF-SD-B-005B)The China Scholarship Council for financial support to M.X.Guo
文摘The effect of adding 0.03wt%Ni on the microstructure and mechanical properties of Al–Mg–Si–Cu–Zn alloys was systematically studied.The results reveal that the number density of spherical Fe-rich phases within grains increases with the addition of Ni,accompanied by the formation of Q(Al3Mg9Si7Cu2)precipitates around the spherical Fe-rich phases.Additionally,Ni addition is beneficial to reducing the grain size in the as-cast state.During the homogenization process,Q phases could be completely dissolved and the grain size could remain basically unchanged.However,compared with the Ni-free alloy,the Fe-rich phase in the Ni-containing alloy is more likely to undergo the phase transformation and further form more spherical particles during homogenization treatment.After thermomechanical processing,the distribution of Fe-rich phases in the Ni-containing alloy was further greatly improved and directly resulted in a greater formability than that of the Ni-free alloy.Accordingly,a reasonable Ni addition positively affected the microstructure and formability of the alloys.
文摘This study is a contribution to improving rice productivity on acidic plateau soils of the tropical rainforest zone. It is based on taking into account the cationic balances of the soil in order to optimize the phosphorus (P) nutrition of rice on these acidic soils, where this nutrient constitutes a limiting factor for agricultural production. Three (3) pot trials were conducted in Adiopodoumé in the forested south of Côte d’Ivoire. The interactive effects of calcium carbonate (0, 25, 50 and 75 kg Ca ha<sup>−1</sup>) and magnesium sulfate (0, 25, 50 and 75 kg Mg ha<sup>−1</sup>) were evaluated on the response of NERICA 5 rice at doses 0, 25, 50 and 75 kg P ha<sup>−1</sup> of natural phosphate from Togo, applied only once at the start of the experiment. Additional fertilizers of nitrogen (N) (100 kg N ha<sup>−1</sup>) and potassium (K) (50 kg KCl ha<sup>−1</sup>) were added to each of the tests in a split-plot device. The test results revealed a paddy production potential of approximately 3 to 5 t⋅ha<sup>−1</sup> for NERICA 5 on an acidic soil, under the effect of the interaction of P, Ca and Mg. The quadratic response of rice yield to the doses of these fertilizers would be more dependent on their balance, itself influenced by Ca nutrition. For the sustainability and maintenance of rice production in agro-ecology studied, it was recommended doses of 38 kg Ca ha<sup>−1</sup>, 34 kg Mg ha<sup>−1</sup> in a Ca/Mg ratio (1/1) with intakes of 41 kg P ha<sup>−1</sup>, overall in a ratio 1/1/1 (P/Ca/Mg) more favorable to the availability of free iron considered a guiding element of mineral nutrition. Thus, these promising results should be confirmed in a real environment for better management of the fertilization of rice cultivated on acidic plateau soils in Côte d’Ivoire.
基金financially supported by the Fundamental Research Funds for the Central Universities,China(No.2020CDJDPT001)the Chongqing Natural Science Foundation,China(No.cstc2021jcyj-msxm X0699)。
基金financially supported by the National Natural Science Foundation of China (No. 51771147)
文摘Al-Mg-Si-Sc alloys with different Mg/Si ratio(<1.73 in wt.% vs>1.73 in wt.%) and different grain size(coarse grains vs ultrafine grains) were prepared, which allowed to investigate the grain size-dependent Mg/Si ratio effect on the microstructural evolution and concomitantly on the hardness and electrical conductivity when subjected to aging at 200℃. In the coarse-grained Al-Mg-Sc-Sc alloys, the β" precipitation within the grain interior and also the precipitation hardening were highly dependent on the Mg/Si ratio,while the electrical conductivity was slightly affected by the Mg/Si ratio. A promoted β" precipitation was found in the case of Si excess(Mg/Si ratio <1.73), much greater than in the case of Mg excess(Mg/Si ratio>1.73). While in the ultrafine-grained Al-Mg-Si-Sc alloys, the electrical conductivity rather than the hardness was more sensitive to the Mg/Si ratio. The alloy with Si excess displayed electrical conductivity much higher than its counterpart with Mg excess. This is rationalized by the grain boundary precipitation promoted by Si, which reduced the solute atoms and precipitates within the grain interior. Age softening was found in the ultrafine-grained alloy with Si excess, but the ultrafine-grained alloy with Mg excess held the hardness almost unchanged during the aging. The hardness-conductivity correlation is comprehensively discussed by considering the coupling effect of Mg/Si ratio and grain size. A strategy to simultaneously increase the hardness/strength and electrical conductivity is proposed for the Al-Mg-SiSc alloys, based on present understanding of the predominant factors on strengthening and conductivity,respectively.
