Aluminum-silicon （Al-Si） alloy is very difficult to machine and diamond tools are considered by far the best choice for the machining of these materials. Experimental results in the machining of the Al-Si alloy with...Aluminum-silicon （Al-Si） alloy is very difficult to machine and diamond tools are considered by far the best choice for the machining of these materials. Experimental results in the machining of the Al-Si alloy with diamond coated inserts are presented. Considering the fact that high adhesive strength and fine surface morphology play an importance role in the applications of chemical vapor deposition （CVD） diamond films, multilayer technique combining the hot filament CVD （HFCVD） method is proposed, by which multilayer diamond-coating on silicon nitride inserts is obtained, microcrystalline diamond （MCD）/ nanocrystalline diamond （NCD） film. Also, the conventional monolayer NCD and MCD coated inserts are produced for comparison. The as-deposited diamond films are characterized by field emission scanning electron microscopy （FE-SEM） and Raman spectrum. All the CVD diamond coated inserts and uncoated insert endure the aluminum-silicon alloy turning to estimate their cutting performances. Among all the tested inserts, the MCD/NCD coated insert exhibits the perfect behavior as tool wear due to its very low flank wear and no diamond peeling.展开更多
Dissolved hydrogen is harmful to mechanical properties of refinedhypereutectic aluminum-silicon alloys. In the present work, by using a stepped-form mold and thehydrogen-detecting instrument HYSCAN II, the relationshi...Dissolved hydrogen is harmful to mechanical properties of refinedhypereutectic aluminum-silicon alloys. In the present work, by using a stepped-form mold and thehydrogen-detecting instrument HYSCAN II, the relationship between the initial hydrogen content inthe melt and the refinement effect on the casting of hypereutectic aluminum-silicon alloy wasinvestigated. The experimental results show that the cooling rate, the hydrogen content and thegrain refinement effect are three interactive factors. When the hydrogen content is above 0.20mL/100 g and the cooling rate is lower than that in 50 mm-thick step, hydrogen dissolved in thealloy melt influences the grain refinement effect. With increasing the cooling rate, the criticalhydrogen content increases too. It is expected that much hydrogen in the melt make the netinterfacial energy larger than or equal to zero, resulting in the shielding of the particles AlPduring solidification and that the critical gas content is closely related to the critical radius ofembryo bubbles.展开更多
By making castings that pick up gas from moisture in red sand molds,the porosity generated at different cooling rates was discussed during solidification of hypereutectic Al-25%Si alloy without and with phosphorus add...By making castings that pick up gas from moisture in red sand molds,the porosity generated at different cooling rates was discussed during solidification of hypereutectic Al-25%Si alloy without and with phosphorus additions. The effect of phosphorus addition on hydrogen content in the melt was also studied. It was observed that the phosphorus addition made hydrogen content in alloy melts present a “see-saw' tendency.In addition to primary silicon refinement,the phosphorus promoted gas porosity formed not only in slowly cooled sections, but also in rapidly cooled sections. There was a small difference in density of full dense sample between P-refined and unrefined castings, with a larger density associated with phosphorous addition. The change of the surface tension seemed more reasonable to explain the mechanism of porosity behavior.展开更多
The difference of conductivity between primary iron-rich phases and aluminum melt has been used to separate them by electromagnetic force (EMF) which is induced by imposing a direct electric current and a steady magne...The difference of conductivity between primary iron-rich phases and aluminum melt has been used to separate them by electromagnetic force (EMF) which is induced by imposing a direct electric current and a steady magnetic field in molten Al-Si alloy. Theoretical analysis and experiments on self-designed electromagnetic separation indicates that primary needle-like β phases are difficult to separate; while primary α iron-rich phases can be separated by electromagnetic separation. Primary iron-rich phases have been removed from the melt successfully when the molten metal flows horizontally through separation channel. The iron content is reduced from 1.13% to 0.41%.展开更多
A high Fe containing aluminum matrix filler metal for hardfacing aluminum silicon alloys has been developed by using iron,nickel,and silicon as the major strengthening elements,and by measuring mechanical properties...A high Fe containing aluminum matrix filler metal for hardfacing aluminum silicon alloys has been developed by using iron,nickel,and silicon as the major strengthening elements,and by measuring mechanical properties,room temperature and high temperature wear tests,and microstructural analysis.The filler metal,which contains 3.0%-5.0% Fe and 11.0%-13.0% Si,exhibits an excellent weldability.The as cast and as welded microstructures for the filler metal are of uniformly distribution and its dispersed network of hard phase is enriched with Al Si Fe Ni.The filler metal shows high mechanical properties and wear resistance at both room temperature and high temperatures.The deposited metal has a better resistance to impact wear at 220℃ than that of substrate Al Si Mg Cu piston alloy;at room temperature,the deposited metal has an equivalent resistance to slide wear with lubrication as that of a hyper eutectic aluminum silicon alloy with 27% Si and 1% Ni.展开更多
采用熔体水淬法(水冷法)、气雾化法和单辊熔融纺丝技术(甩带法)制备不同冷却速率的快速凝固过共晶Al-50%Si合金,并通过扫描电子显微镜(scanning electron microscope,SEM)和X射线衍射仪(X-ray diffractometer,XRD)分析了快速凝固与常规...采用熔体水淬法(水冷法)、气雾化法和单辊熔融纺丝技术(甩带法)制备不同冷却速率的快速凝固过共晶Al-50%Si合金,并通过扫描电子显微镜(scanning electron microscope,SEM)和X射线衍射仪(X-ray diffractometer,XRD)分析了快速凝固与常规凝固的差异,以及快速凝固Al-50%Si合金微观组织的演变。结果表明:在水冷的Al-50%Si合金组织中观察到了树枝状的Al相,较大的过冷度导致这种亚共晶组织的形成,此组织属于非稳定状态,且共晶Si完全细化至纤维状;随着冷却速率的增加,在甩带试样中Al相的树枝状组织消失;通过甩带以及气雾化制备的Al-50%Si合金中,初晶Si颗粒被明显细化,由常规凝固的200μm细化至20μm左右,使Si在Al基体中的固溶度增大,造成Al基体晶格发生畸变。展开更多
基金Project(50975177)supported by the National Natural Science Foundation of China
文摘Aluminum-silicon （Al-Si） alloy is very difficult to machine and diamond tools are considered by far the best choice for the machining of these materials. Experimental results in the machining of the Al-Si alloy with diamond coated inserts are presented. Considering the fact that high adhesive strength and fine surface morphology play an importance role in the applications of chemical vapor deposition （CVD） diamond films, multilayer technique combining the hot filament CVD （HFCVD） method is proposed, by which multilayer diamond-coating on silicon nitride inserts is obtained, microcrystalline diamond （MCD）/ nanocrystalline diamond （NCD） film. Also, the conventional monolayer NCD and MCD coated inserts are produced for comparison. The as-deposited diamond films are characterized by field emission scanning electron microscopy （FE-SEM） and Raman spectrum. All the CVD diamond coated inserts and uncoated insert endure the aluminum-silicon alloy turning to estimate their cutting performances. Among all the tested inserts, the MCD/NCD coated insert exhibits the perfect behavior as tool wear due to its very low flank wear and no diamond peeling.
基金This work was financially supported by the National Natural Science Foundation of China (No.50071028)the Natural Science Foundation of Shandong Province in China (No. Z2001F02)
文摘Dissolved hydrogen is harmful to mechanical properties of refinedhypereutectic aluminum-silicon alloys. In the present work, by using a stepped-form mold and thehydrogen-detecting instrument HYSCAN II, the relationship between the initial hydrogen content inthe melt and the refinement effect on the casting of hypereutectic aluminum-silicon alloy wasinvestigated. The experimental results show that the cooling rate, the hydrogen content and thegrain refinement effect are three interactive factors. When the hydrogen content is above 0.20mL/100 g and the cooling rate is lower than that in 50 mm-thick step, hydrogen dissolved in thealloy melt influences the grain refinement effect. With increasing the cooling rate, the criticalhydrogen content increases too. It is expected that much hydrogen in the melt make the netinterfacial energy larger than or equal to zero, resulting in the shielding of the particles AlPduring solidification and that the critical gas content is closely related to the critical radius ofembryo bubbles.
文摘By making castings that pick up gas from moisture in red sand molds,the porosity generated at different cooling rates was discussed during solidification of hypereutectic Al-25%Si alloy without and with phosphorus additions. The effect of phosphorus addition on hydrogen content in the melt was also studied. It was observed that the phosphorus addition made hydrogen content in alloy melts present a “see-saw' tendency.In addition to primary silicon refinement,the phosphorus promoted gas porosity formed not only in slowly cooled sections, but also in rapidly cooled sections. There was a small difference in density of full dense sample between P-refined and unrefined castings, with a larger density associated with phosphorous addition. The change of the surface tension seemed more reasonable to explain the mechanism of porosity behavior.
文摘The difference of conductivity between primary iron-rich phases and aluminum melt has been used to separate them by electromagnetic force (EMF) which is induced by imposing a direct electric current and a steady magnetic field in molten Al-Si alloy. Theoretical analysis and experiments on self-designed electromagnetic separation indicates that primary needle-like β phases are difficult to separate; while primary α iron-rich phases can be separated by electromagnetic separation. Primary iron-rich phases have been removed from the melt successfully when the molten metal flows horizontally through separation channel. The iron content is reduced from 1.13% to 0.41%.
文摘A high Fe containing aluminum matrix filler metal for hardfacing aluminum silicon alloys has been developed by using iron,nickel,and silicon as the major strengthening elements,and by measuring mechanical properties,room temperature and high temperature wear tests,and microstructural analysis.The filler metal,which contains 3.0%-5.0% Fe and 11.0%-13.0% Si,exhibits an excellent weldability.The as cast and as welded microstructures for the filler metal are of uniformly distribution and its dispersed network of hard phase is enriched with Al Si Fe Ni.The filler metal shows high mechanical properties and wear resistance at both room temperature and high temperatures.The deposited metal has a better resistance to impact wear at 220℃ than that of substrate Al Si Mg Cu piston alloy;at room temperature,the deposited metal has an equivalent resistance to slide wear with lubrication as that of a hyper eutectic aluminum silicon alloy with 27% Si and 1% Ni.
文摘采用熔体水淬法(水冷法)、气雾化法和单辊熔融纺丝技术(甩带法)制备不同冷却速率的快速凝固过共晶Al-50%Si合金,并通过扫描电子显微镜(scanning electron microscope,SEM)和X射线衍射仪(X-ray diffractometer,XRD)分析了快速凝固与常规凝固的差异,以及快速凝固Al-50%Si合金微观组织的演变。结果表明:在水冷的Al-50%Si合金组织中观察到了树枝状的Al相,较大的过冷度导致这种亚共晶组织的形成,此组织属于非稳定状态,且共晶Si完全细化至纤维状;随着冷却速率的增加,在甩带试样中Al相的树枝状组织消失;通过甩带以及气雾化制备的Al-50%Si合金中,初晶Si颗粒被明显细化,由常规凝固的200μm细化至20μm左右,使Si在Al基体中的固溶度增大,造成Al基体晶格发生畸变。
