Semi-solid squeeze casting（SSSC） and liquid squeeze casting（LSC） processes were used to fabricate a ZL104 connecting rod, and the influences of the process parameters on the microstructures and mechanical properti...Semi-solid squeeze casting（SSSC） and liquid squeeze casting（LSC） processes were used to fabricate a ZL104 connecting rod, and the influences of the process parameters on the microstructures and mechanical properties were investigated. Results showed that the tensile strength and elongation of the SSSC-fabricated rod were improved by 22% and 17%, respectively, compared with those of the LSC-fabricated rod. For SSSC, the average particle size（APS） and the shape factor（SF） increased with the increase of re-melting temperature（Tr）, whereas the tensile strength and elongation increased first and then decreased. The APS increased with increasing the mold temperature（Tm）, whereas the SF increased initially and then decreased, which caused the tensile strength and elongation to increase initially and then decrease. The APS decreased and the SF increased as squeezing pressure（ps） increased, and the mechanical properties were enhanced. Moreover, the optimal Tr, ps and Tm are 848 K, 100 MPa and 523 K, respectively.展开更多
Daytime activity budgets of feral goats （ Capra hircus ） were studied in 1981, 1982 and 2000 on the Isle of Rum, northwest Scotland. This paper analyzes the influence of key weather variables （temperature and rainf...Daytime activity budgets of feral goats （ Capra hircus ） were studied in 1981, 1982 and 2000 on the Isle of Rum, northwest Scotland. This paper analyzes the influence of key weather variables （temperature and rainfall） and seasonal variations in daylength on daytime activity budgets. This study showed that the percentage of daytime spent in feeding by feral goats on Rum Island decreased with average monthly temperature, while the percentage of daytime spent in lying increased and rainfall had no significant effects on the percentage daytime spent in feeding or lying. The daylength varied greatly from January to December with the longest daylength being in June and July, and the shortest one in December and January. The amount of daytime spent feeding decreased from summer to winter, although the percentage of daytime spent feeding increased greatly from summer to winter. The seasonal variations in daylength seem to be an important factor in constraining feral goats＇ activity, especially in the cold and wet winters when forage biomass and quality are both at their lowest level. We discuss the influence of such constraining effects on the forage intake of these goats and their winter survival rate, as well as its implication for population regulation of these goats.展开更多
To obtain magnesium alloys with a low density and improved mechanical properties,Y element was added into Mg−4Li−3Al(wt.%)alloys,and the effect of Y content on microstructure evolution and mechanical properties was in...To obtain magnesium alloys with a low density and improved mechanical properties,Y element was added into Mg−4Li−3Al(wt.%)alloys,and the effect of Y content on microstructure evolution and mechanical properties was investigated by using optical microscopy,scanning electron microscopy and tensile tests.The results show that mechanical properties of as-cast Mg−4Li−3Al alloys with Y addition are significantly improved as a result of hot extrusion.The best comprehensive mechanical properties are obtained in hot-extruded Mg−4Li−3Al−1.5Y alloy,which possesses high ultimate tensile strength(UTS=248 MPa)and elongation(δ=27%).The improvement of mechanical properties of hot-extruded Mg−4Li−3Al−1.5Y alloy was mainly attributed to combined effects of grain refinement,solid solution strengthening and precipitation strengthening.展开更多
Mg-4 Li-3(Al-Si),Mg-8 Li-3(Al-Si)and Mg-12 Li-3(Al-Si)alloys based on theα-Mg,α-Mg+β-Li,β-Li phases,respectively,were produced to investigate the effect of alloying with Al-Si eutectic on the microstructure and me...Mg-4 Li-3(Al-Si),Mg-8 Li-3(Al-Si)and Mg-12 Li-3(Al-Si)alloys based on theα-Mg,α-Mg+β-Li,β-Li phases,respectively,were produced to investigate the effect of alloying with Al-Si eutectic on the microstructure and mechanical properties of the three alloys.Alloying with the Al-Si eutectic of Mg-xLi(x=4,8 and 12 wt.%)alloys caused the formation of different types of Al-Li precipitates:Al3Li,AlLi and Li3Al2,respectively.Also,considerable quantities of Mg2Si phase particles were found in the three alloys.The results of tensile tests showed that the Mg-4Li-3(Al-Si)alloy exhibited the highest ultimate tensile strength(UTS)of 249 MPa but the lowest elongation of 6.3%.The Mg-12Li-3(Al-Si)alloy had the highest elongation of 26%but the lowest UTS of 173 MPa.The different mechanical properties were attributed to the different crystal structures of the three alloys and the precipitate with different type,morphology and distribution.展开更多
基金Project(51335009)supported by the National Natural Science Foundation of ChinaProject(2014JQ7273)supported by the Natural Science Foundation of Shaanxi Province of ChinaProject(CXY1514(1))supported by the Xi’an Science and Technology Plan Projects,China
文摘Semi-solid squeeze casting（SSSC） and liquid squeeze casting（LSC） processes were used to fabricate a ZL104 connecting rod, and the influences of the process parameters on the microstructures and mechanical properties were investigated. Results showed that the tensile strength and elongation of the SSSC-fabricated rod were improved by 22% and 17%, respectively, compared with those of the LSC-fabricated rod. For SSSC, the average particle size（APS） and the shape factor（SF） increased with the increase of re-melting temperature（Tr）, whereas the tensile strength and elongation increased first and then decreased. The APS increased with increasing the mold temperature（Tm）, whereas the SF increased initially and then decreased, which caused the tensile strength and elongation to increase initially and then decrease. The APS decreased and the SF increased as squeezing pressure（ps） increased, and the mechanical properties were enhanced. Moreover, the optimal Tr, ps and Tm are 848 K, 100 MPa and 523 K, respectively.
文摘Daytime activity budgets of feral goats （ Capra hircus ） were studied in 1981, 1982 and 2000 on the Isle of Rum, northwest Scotland. This paper analyzes the influence of key weather variables （temperature and rainfall） and seasonal variations in daylength on daytime activity budgets. This study showed that the percentage of daytime spent in feeding by feral goats on Rum Island decreased with average monthly temperature, while the percentage of daytime spent in lying increased and rainfall had no significant effects on the percentage daytime spent in feeding or lying. The daylength varied greatly from January to December with the longest daylength being in June and July, and the shortest one in December and January. The amount of daytime spent feeding decreased from summer to winter, although the percentage of daytime spent feeding increased greatly from summer to winter. The seasonal variations in daylength seem to be an important factor in constraining feral goats＇ activity, especially in the cold and wet winters when forage biomass and quality are both at their lowest level. We discuss the influence of such constraining effects on the forage intake of these goats and their winter survival rate, as well as its implication for population regulation of these goats.
基金The work was supported by the National Natural Science Foundation of China(No.51401115)the Promoted Research Fund for Excellent Young and Middle-aged Scientists of Shandong Province,China(No.BS2013CL034)partially by the Fundamental Research Funds of Shandong University,China(2016JC016).
文摘To obtain magnesium alloys with a low density and improved mechanical properties,Y element was added into Mg−4Li−3Al(wt.%)alloys,and the effect of Y content on microstructure evolution and mechanical properties was investigated by using optical microscopy,scanning electron microscopy and tensile tests.The results show that mechanical properties of as-cast Mg−4Li−3Al alloys with Y addition are significantly improved as a result of hot extrusion.The best comprehensive mechanical properties are obtained in hot-extruded Mg−4Li−3Al−1.5Y alloy,which possesses high ultimate tensile strength(UTS=248 MPa)and elongation(δ=27%).The improvement of mechanical properties of hot-extruded Mg−4Li−3Al−1.5Y alloy was mainly attributed to combined effects of grain refinement,solid solution strengthening and precipitation strengthening.
基金Projects(51971040,51701029,51671041,51531002) supported by the National Natural Science Foundation of ChinaProject(2016YFB0301100) supported by the National Key Research and Development Program of China+2 种基金Projects(2018T110943,2017M620410) supported by the China Postdoctoral Science FoundationProject(Xm2017010) supported by the the Chongqing Postdoctoral Scientific Research Foundation,ChinaProject(2018CDGFCL005) supported by the Fundamental Research Funds for the Central Universities,China
文摘Mg-4 Li-3(Al-Si),Mg-8 Li-3(Al-Si)and Mg-12 Li-3(Al-Si)alloys based on theα-Mg,α-Mg+β-Li,β-Li phases,respectively,were produced to investigate the effect of alloying with Al-Si eutectic on the microstructure and mechanical properties of the three alloys.Alloying with the Al-Si eutectic of Mg-xLi(x=4,8 and 12 wt.%)alloys caused the formation of different types of Al-Li precipitates:Al3Li,AlLi and Li3Al2,respectively.Also,considerable quantities of Mg2Si phase particles were found in the three alloys.The results of tensile tests showed that the Mg-4Li-3(Al-Si)alloy exhibited the highest ultimate tensile strength(UTS)of 249 MPa but the lowest elongation of 6.3%.The Mg-12Li-3(Al-Si)alloy had the highest elongation of 26%but the lowest UTS of 173 MPa.The different mechanical properties were attributed to the different crystal structures of the three alloys and the precipitate with different type,morphology and distribution.
