The effect of pouring temperature, electromagnetic stirring power and holding process on semi-solid A356 aluminum alloy slurry was investigated, then the slurry was squeeze-cast. The results show that when the pouring...The effect of pouring temperature, electromagnetic stirring power and holding process on semi-solid A356 aluminum alloy slurry was investigated, then the slurry was squeeze-cast. The results show that when the pouring temperatures are properly above the liquidus line, for example 630-650 ℃, the slurry with spherical primary α（Al） grains can be prepared under the stirring power of 1.27 kW. The slurry is then homogeneously held for a short time, and the primary α（Al） grains are further ripened and distributed evenly in the slurry. The results of the rheo-squeezed casting experiments show that the injection specific pressure has a great effect on the filling ability of the semi-solid A356 aluminum alloy slurry, and the higher the injection specific pressure is, the better the ability for the slurry to fill the mould cavity is. When the injection specific pressure is equal to or above 34 MPa, the whole and compact rheo-squeezed castings can be obtained. The microstructure of the castings indicates that the shape, size and numbers of the primary α（Al） grains in different parts of the castings are highly consistent. After being held at 535 ℃ for 5 h and then aged at 155 ℃ for 12 h, the ultimate strength of the rheo-squeezed castings can reach 300-320 MPa, the yield strength 230-255 MPa, and the elongation 11%-15%.展开更多
This paper discusses the technique of casting concrete ofmicropiles with pressures and the consequence of comparisons with normal way of casting concrete （casting with gravity）. Preliminary geotechnical studies have...This paper discusses the technique of casting concrete ofmicropiles with pressures and the consequence of comparisons with normal way of casting concrete （casting with gravity）. Preliminary geotechnical studies have been made in specific area in Sudan to predict the soil parameters and then an experimental work has been done for an estimated number ofmicropiles with different diameters and different techniques of placing concrete with various amount of pressure. This study was carried out to learn the usefulness of this technique in the field of structural foundations in Sudan. Capacities of micropiles were compared in cases of non-pressure casting （normal way of casting concrete） and pressure casting. Through the results, it was found that the entry of pressure factor in the operation of casting concrete increases the capacities of micropiles. The increased value of ultimate load depends on the amount of pressure applied.展开更多
基金Project(2006AA03Z115) supported by the National Hi-tech Research and Development Program of ChinaProject(2006CB605203) supported by the National Basic Research Program of ChinaProject(50774007) supported by the National Natural Science Foundation of China
文摘The effect of pouring temperature, electromagnetic stirring power and holding process on semi-solid A356 aluminum alloy slurry was investigated, then the slurry was squeeze-cast. The results show that when the pouring temperatures are properly above the liquidus line, for example 630-650 ℃, the slurry with spherical primary α（Al） grains can be prepared under the stirring power of 1.27 kW. The slurry is then homogeneously held for a short time, and the primary α（Al） grains are further ripened and distributed evenly in the slurry. The results of the rheo-squeezed casting experiments show that the injection specific pressure has a great effect on the filling ability of the semi-solid A356 aluminum alloy slurry, and the higher the injection specific pressure is, the better the ability for the slurry to fill the mould cavity is. When the injection specific pressure is equal to or above 34 MPa, the whole and compact rheo-squeezed castings can be obtained. The microstructure of the castings indicates that the shape, size and numbers of the primary α（Al） grains in different parts of the castings are highly consistent. After being held at 535 ℃ for 5 h and then aged at 155 ℃ for 12 h, the ultimate strength of the rheo-squeezed castings can reach 300-320 MPa, the yield strength 230-255 MPa, and the elongation 11%-15%.
文摘This paper discusses the technique of casting concrete ofmicropiles with pressures and the consequence of comparisons with normal way of casting concrete （casting with gravity）. Preliminary geotechnical studies have been made in specific area in Sudan to predict the soil parameters and then an experimental work has been done for an estimated number ofmicropiles with different diameters and different techniques of placing concrete with various amount of pressure. This study was carried out to learn the usefulness of this technique in the field of structural foundations in Sudan. Capacities of micropiles were compared in cases of non-pressure casting （normal way of casting concrete） and pressure casting. Through the results, it was found that the entry of pressure factor in the operation of casting concrete increases the capacities of micropiles. The increased value of ultimate load depends on the amount of pressure applied.
