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
将添加稀土元素Nd后的Al-18Si-3Mg合金使用强流脉冲电子束(high-current pulsed electron beam,HCPEB)处理,以达到改善微观组织结构以及提升合金性能的目的.本实验利用扫描电子显微镜(scanning electron microscope,SEM),X射线衍射(X-ra...将添加稀土元素Nd后的Al-18Si-3Mg合金使用强流脉冲电子束(high-current pulsed electron beam,HCPEB)处理,以达到改善微观组织结构以及提升合金性能的目的.本实验利用扫描电子显微镜(scanning electron microscope,SEM),X射线衍射(X-ray diffraction,XRD),显微硬度计等一系列检测手段研究了添加Nd元素对Al-18Si-3Mg合金的组织结构及力学性能的影响.SEM结果表明,Nd元素能够起到细化初晶硅的作用,同时可有效消除熔坑结构.XRD结果表明,将Nd元素添加到铝硅合金中,没有相变产生,衍射峰随脉冲次数的增加将出现一定程度宽化和偏移现象.显微硬度测试结果表明,Nd元素的添加会导致硬度降低,同时通过控制脉冲次数的增加,合金显微硬度也会递增.另外,通过往复摩擦试验发现,Nd元素能够提升合金的耐磨性.稀土元素Nd的添加能够明显改善电子束处理形成的熔坑结构,并且使用电子束处理添加金属Mg和稀土Nd过共晶铝硅合金,能有效提升合金的机械性能.展开更多
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.
文摘将添加稀土元素Nd后的Al-18Si-3Mg合金使用强流脉冲电子束(high-current pulsed electron beam,HCPEB)处理,以达到改善微观组织结构以及提升合金性能的目的.本实验利用扫描电子显微镜(scanning electron microscope,SEM),X射线衍射(X-ray diffraction,XRD),显微硬度计等一系列检测手段研究了添加Nd元素对Al-18Si-3Mg合金的组织结构及力学性能的影响.SEM结果表明,Nd元素能够起到细化初晶硅的作用,同时可有效消除熔坑结构.XRD结果表明,将Nd元素添加到铝硅合金中,没有相变产生,衍射峰随脉冲次数的增加将出现一定程度宽化和偏移现象.显微硬度测试结果表明,Nd元素的添加会导致硬度降低,同时通过控制脉冲次数的增加,合金显微硬度也会递增.另外,通过往复摩擦试验发现,Nd元素能够提升合金的耐磨性.稀土元素Nd的添加能够明显改善电子束处理形成的熔坑结构,并且使用电子束处理添加金属Mg和稀土Nd过共晶铝硅合金,能有效提升合金的机械性能.
