The surface and interior temperature-time curves of blocky cerium modified AZ91D magnesium alloy weremeasured during a non-protective heating and melting process. Two inflection points with rapid increase in temperatu...The surface and interior temperature-time curves of blocky cerium modified AZ91D magnesium alloy weremeasured during a non-protective heating and melting process. Two inflection points with rapid increase in temperaturewere found on both curves, which corresponded to the formation of "auliflower" oxide on the surface and the occurrenceof flame during melting. These two temperatures are therefore defined as oxidation point and ignition point, respectively.The interior temperature-time curve is similar to that measured on the surface except for a comparable time delay. Theoxidation and ignition temperatures increase with Ce content, an average increase of 33℃ and 61℃ was found whenCe addition was about 1.0 wt %. However, the increasing rate of the oxidation and ignition temperature decreases withincreasing Ce content. An addition of 0.6wt% Ce is recommended for ignition-resistant AZ91 magnesium alloy.展开更多
The microstructures and mechanical properties of 550 MPa grade lightweight high strength thin-walled H-beam steel were experimentally studied. The experimental results show that the microstructure of the air-cooled H-...The microstructures and mechanical properties of 550 MPa grade lightweight high strength thin-walled H-beam steel were experimentally studied. The experimental results show that the microstructure of the air-cooled H-beam steel sample is consisted of ferrite, pearlite and a small amount of granular bainites as well as fine and dispersive V（C,N） precipitates. The microstructure of the water-cooled steel sample is consisted of ferrite and bainite as well as a small amount of fine pearlites. The microstructure of the water-cooled sample is finer than that of the air-cooled sample with the average intercept size of the surface grains reaching to 3.5 gna. The finish rolling temperature of the thin-walled high strength H-beam steel is in the range of 750 ~C-850 ~C. The lower the finish rolling temperature and the faster the cooling rate, the finer the ferrite grains, the volume fraction of bainite is increased through water cooling process. Grain refinement strengthening and precipitation strengthening are used as major strengthening means to develop 550 MPa grade lightweight high strength thin- walled H-beam steel. Vanadium partially soluted in the matrix and contributes to the solution strengthening. The 550 MPa grade high-strength thin-walled H-beam steel could be developed by direct air cooling after hot rolling to fully meet the requirements of the target properties.展开更多
开发了一种高效、低成本的铝合金均匀凝固控制制备大体积半固态浆料工艺——气冷搅拌棒工艺(Air-cooled stirring rod process,ACSR),将该制浆工艺与压铸机衔接形成多条一体化智能流变压铸生产线进行铝合金大型薄壁件流变压铸高效制备...开发了一种高效、低成本的铝合金均匀凝固控制制备大体积半固态浆料工艺——气冷搅拌棒工艺(Air-cooled stirring rod process,ACSR),将该制浆工艺与压铸机衔接形成多条一体化智能流变压铸生产线进行铝合金大型薄壁件流变压铸高效制备。目前,ACSR工艺可实现在30 s内制备出40 kg固相率为25%~35%的大体积半固态浆料。该流变压铸工艺已在新能源汽车、5G通信等高品质铝合金大型薄壁件的制备领域得到产业化应用,制备的典型产品包括5G通信用散热壳体、滤波器壳体、天线机箱与新能源汽车用三电结构壳体、端盖、ABS系统阀体等。与传统压铸件相比,新工艺制备的铝合金铸件显微组织细小圆整、表面品质好、内部气孔少,且具有更为优异的力学性能和导热系数。展开更多
This paper studies the composition, quantity and particle size distribution of nano-scaled precipitates with size less than 20 nm in high strength low carbon (HSLC) steel and their effects on mechanical properties of ...This paper studies the composition, quantity and particle size distribution of nano-scaled precipitates with size less than 20 nm in high strength low carbon (HSLC) steel and their effects on mechanical properties of HSLC steel by means of mass balance calculation of nano-scaled precipitates measured by chemical phase analysis plus SAXS method, high-resolution TEM analysis and thermodynamics calculation, as well as temper rapid cooling treatment of ZJ330. It is found that there existed a large quantity of nano-scaled iron-carbon precipitates with size less than 18 nm in low carbon steel produced by CSP and they are mainly Fe-O-C and Fe-Ti-O-C precipitates formed below temperature A1. These precipitates have ob- vious precipitation strengthening effect on HSLC steel and this may be regarded as one of the main reasons why HSLC steel has higher strength. There also existed a lot of iron-carbon precipitates with size less than 36 nm in HSLA steels.展开更多
基金the Hi-Tech Research and Development Program of China (grant No.2002AA336080) the National Basic Research Program of China (grant No. G2000067202) and Jiangxi Provincial Department of Education.
文摘The surface and interior temperature-time curves of blocky cerium modified AZ91D magnesium alloy weremeasured during a non-protective heating and melting process. Two inflection points with rapid increase in temperaturewere found on both curves, which corresponded to the formation of "auliflower" oxide on the surface and the occurrenceof flame during melting. These two temperatures are therefore defined as oxidation point and ignition point, respectively.The interior temperature-time curve is similar to that measured on the surface except for a comparable time delay. Theoxidation and ignition temperatures increase with Ce content, an average increase of 33℃ and 61℃ was found whenCe addition was about 1.0 wt %. However, the increasing rate of the oxidation and ignition temperature decreases withincreasing Ce content. An addition of 0.6wt% Ce is recommended for ignition-resistant AZ91 magnesium alloy.
基金Funded by the "11th Five" National Science and Technology Support Project(No.2006BAE03A13)
文摘The microstructures and mechanical properties of 550 MPa grade lightweight high strength thin-walled H-beam steel were experimentally studied. The experimental results show that the microstructure of the air-cooled H-beam steel sample is consisted of ferrite, pearlite and a small amount of granular bainites as well as fine and dispersive V（C,N） precipitates. The microstructure of the water-cooled steel sample is consisted of ferrite and bainite as well as a small amount of fine pearlites. The microstructure of the water-cooled sample is finer than that of the air-cooled sample with the average intercept size of the surface grains reaching to 3.5 gna. The finish rolling temperature of the thin-walled high strength H-beam steel is in the range of 750 ~C-850 ~C. The lower the finish rolling temperature and the faster the cooling rate, the finer the ferrite grains, the volume fraction of bainite is increased through water cooling process. Grain refinement strengthening and precipitation strengthening are used as major strengthening means to develop 550 MPa grade lightweight high strength thin- walled H-beam steel. Vanadium partially soluted in the matrix and contributes to the solution strengthening. The 550 MPa grade high-strength thin-walled H-beam steel could be developed by direct air cooling after hot rolling to fully meet the requirements of the target properties.
基金Supported by the National Natural Science Foundation of China (Grant No. 50334010)the State Foundation for Key Projects: New Generation of Steels (Grant No. G1998061500)
文摘This paper studies the composition, quantity and particle size distribution of nano-scaled precipitates with size less than 20 nm in high strength low carbon (HSLC) steel and their effects on mechanical properties of HSLC steel by means of mass balance calculation of nano-scaled precipitates measured by chemical phase analysis plus SAXS method, high-resolution TEM analysis and thermodynamics calculation, as well as temper rapid cooling treatment of ZJ330. It is found that there existed a large quantity of nano-scaled iron-carbon precipitates with size less than 18 nm in low carbon steel produced by CSP and they are mainly Fe-O-C and Fe-Ti-O-C precipitates formed below temperature A1. These precipitates have ob- vious precipitation strengthening effect on HSLC steel and this may be regarded as one of the main reasons why HSLC steel has higher strength. There also existed a lot of iron-carbon precipitates with size less than 36 nm in HSLA steels.
