对触头材料的熔渗机理、熔渗过程进行了详细的分析 ,并以制造 Cu Cr50和 Cu W系触头为例 ,提出了确定触头材料熔浸过程工艺参数的原则和方法 :确定烧结工艺参数时要兼顾氧化膜的去除、保证骨架强度和孔隙通道 ,要考虑不同粉末粒径及生...对触头材料的熔渗机理、熔渗过程进行了详细的分析 ,并以制造 Cu Cr50和 Cu W系触头为例 ,提出了确定触头材料熔浸过程工艺参数的原则和方法 :确定烧结工艺参数时要兼顾氧化膜的去除、保证骨架强度和孔隙通道 ,要考虑不同粉末粒径及生坯特性 ;而确定熔渗工艺参数时则要考虑骨架金属粉末的粒径、生坯的高度、牌号及熔渗剂熔点。展开更多
In fabricating magnesium-matrix composites, an easy and cost-effective route is to infiltrate the ceramic preform with molten Mg without any external pressure. However, a rather well wettability of molten Mg with cera...In fabricating magnesium-matrix composites, an easy and cost-effective route is to infiltrate the ceramic preform with molten Mg without any external pressure. However, a rather well wettability of molten Mg with ceramic reinforcement is needed for this process. In order to improve the wettability of the metal melt with ceramic preform during fabricating composites by metal melt infiltration, a simple and viable method has been proposed in this paper where a small amount of metal powder with higher melting point is added to the ceramic preform such that the surface tension of the Mg melt and the liquid-solid interfacial tension could be reduced. By using this method, boron carbide particulate-reinforced magnesium-matrix composites （B4C/Mg） have been successfully fabricated where Ti powder immiscible with magnesium melt was introduced into B4C preform as infiltration inducer. The infiltration ability of molten Mg to the ceramic preform was further studied in association with the processing conditions and the mechanism involved in this process was also analyzed.展开更多
C/C composites with banded structure pyrocarbon were fabricated by fast chemical vapor infiltration（CVI）,with C3H6 as carbon source,N2 as carrier gas,and three-dimensional（3D） 12K PAN-based carbon fabric with high...C/C composites with banded structure pyrocarbon were fabricated by fast chemical vapor infiltration（CVI）,with C3H6 as carbon source,N2 as carrier gas,and three-dimensional（3D） 12K PAN-based carbon fabric with high density of 0.94 g/cm3 as preform.Experimental results indicated that the fracture characteristics of C/C composites were closely related to the frequency of high-temperature treatment（HTT） at the break of CVI process.According to the load？displacement curves,C/C composites showed a pseudoplastic fracture after twice of HTT.After three times of HTT,load？displacement curves tended to be stable with a decreasing bending strength at 177.5 MPa.Delamination failure and intrastratal fiber fracture were observed at the cross-section of C/C composites by scanning electronic microscope.Because the content of pyrocarbon and fibers has a different distribution in layers,the C/C composites show different fracture characteristics at various regions,which leads to good toughness and bending strength.展开更多
文摘对触头材料的熔渗机理、熔渗过程进行了详细的分析 ,并以制造 Cu Cr50和 Cu W系触头为例 ,提出了确定触头材料熔浸过程工艺参数的原则和方法 :确定烧结工艺参数时要兼顾氧化膜的去除、保证骨架强度和孔隙通道 ,要考虑不同粉末粒径及生坯特性 ;而确定熔渗工艺参数时则要考虑骨架金属粉末的粒径、生坯的高度、牌号及熔渗剂熔点。
基金Financial support from the National Natural Science Foundation of China(Grant No.51271051)
文摘In fabricating magnesium-matrix composites, an easy and cost-effective route is to infiltrate the ceramic preform with molten Mg without any external pressure. However, a rather well wettability of molten Mg with ceramic reinforcement is needed for this process. In order to improve the wettability of the metal melt with ceramic preform during fabricating composites by metal melt infiltration, a simple and viable method has been proposed in this paper where a small amount of metal powder with higher melting point is added to the ceramic preform such that the surface tension of the Mg melt and the liquid-solid interfacial tension could be reduced. By using this method, boron carbide particulate-reinforced magnesium-matrix composites （B4C/Mg） have been successfully fabricated where Ti powder immiscible with magnesium melt was introduced into B4C preform as infiltration inducer. The infiltration ability of molten Mg to the ceramic preform was further studied in association with the processing conditions and the mechanism involved in this process was also analyzed.
基金Project (50802115) supported by the National Natural Science Foundation of ChinaProject (2011CB605801) supported by the National Basic Research Program of China
文摘C/C composites with banded structure pyrocarbon were fabricated by fast chemical vapor infiltration（CVI）,with C3H6 as carbon source,N2 as carrier gas,and three-dimensional（3D） 12K PAN-based carbon fabric with high density of 0.94 g/cm3 as preform.Experimental results indicated that the fracture characteristics of C/C composites were closely related to the frequency of high-temperature treatment（HTT） at the break of CVI process.According to the load？displacement curves,C/C composites showed a pseudoplastic fracture after twice of HTT.After three times of HTT,load？displacement curves tended to be stable with a decreasing bending strength at 177.5 MPa.Delamination failure and intrastratal fiber fracture were observed at the cross-section of C/C composites by scanning electronic microscope.Because the content of pyrocarbon and fibers has a different distribution in layers,the C/C composites show different fracture characteristics at various regions,which leads to good toughness and bending strength.
