Based on the quantum Sutton-Chen many-body potential,a molecular dynamics simulation was performed to investigate the formation and evolution properties of clusters in liquid Cu with 50 000 atoms.The cluster-type inde...Based on the quantum Sutton-Chen many-body potential,a molecular dynamics simulation was performed to investigate the formation and evolution properties of clusters in liquid Cu with 50 000 atoms.The cluster-type index method(CTIM)was used to describe the complex microstructure transitions.It is demonstrated that the amorphous structures are mainly formed with the three bond-types of 1551,1541 and 1431 in the system,and the icosahedral cluster(12 0 12 0)and other basic polyhedron clusters of(12 2 8 2),(13 1 10 2),(13 3 6 4),(14 1 10 3),(14 2 8 4)and(14 3 6 5)play a critical and leading role in the transition from liquid to glass.The nano-clusters formed in the system consist of some basic clusters and middle cluster configurations by connecting to each other,and distinguish from those obtained by gaseous deposition and ionic spray.From the results of structural parameter pair distribution function g(r),bond-types and basic cluster-types,it is found that the glass transition temperature Tg for liquid metal Cu is about 673 K at the cooling rate of 1.0×1014 K/s.展开更多
A multi-component Cu-based metal powder was chosen for direct laser sintering. The powder consists of a mixture of high-purity Cu powder, pre-alloyed CuSn and CuP powder. Liquid phase sintering with complete melting o...A multi-component Cu-based metal powder was chosen for direct laser sintering. The powder consists of a mixture of high-purity Cu powder, pre-alloyed CuSn and CuP powder. Liquid phase sintering with complete melting of the binder (CuSn) but non-melting of the cores of structural metal (Cu) proves to be a feasible mechanism for laser sintering of this powder system. The microstructural evolution of the sintered powder with variation of laser processing parameters was presented. High sintering activities and sound densification response were obtained by optimizing the laser powers and scan speeds. Using a high laser power accompanied by a high scan speed gives rise to balling effect. At a high laser power with a slow scan speed the sintering mechanism may change into complete melting/solidification, which decreases the obtainable sintered density. The role of additive phosphorus in the laser sintering process is addressed. Phosphorus can act as a fluxing agent and has a preferential reaction with oxygen to form phosphatic slag, protecting the Cu particles from oxidation. The phosphatic slag shows a concentration along grain boundaries due to its light mass as well as the short thermal cycle of SLS.展开更多
分别采用Cu箔和Cu膜作为中间层,在853 K保温情况下进行了S iC颗粒增强铝基复合材料的瞬间液相扩散连接试验.用金相显微镜、扫描电镜、能谱仪、X射线衍射仪和拉伸试验机研究了表面状态、保温时间和压力对接头显微组织和性能的影响.结果表...分别采用Cu箔和Cu膜作为中间层,在853 K保温情况下进行了S iC颗粒增强铝基复合材料的瞬间液相扩散连接试验.用金相显微镜、扫描电镜、能谱仪、X射线衍射仪和拉伸试验机研究了表面状态、保温时间和压力对接头显微组织和性能的影响.结果表明:合适的压力和中间层厚度能有效改善接头的组织和力学性能,接头剪切强度随保温时间延长而提高.表面状态对接头强度有较大影响.采用Cu膜作中间层由于没有氧化膜的影响,可以获得更好的接头性能,在加2 M Pa压力,853 K保温120 m in连接时接头剪切强度可达169.1 M Pa,约为母材强度的81.7%.展开更多
基金Projects(5027102650571037)supported by the National Natural Science Foundation of China
文摘Based on the quantum Sutton-Chen many-body potential,a molecular dynamics simulation was performed to investigate the formation and evolution properties of clusters in liquid Cu with 50 000 atoms.The cluster-type index method(CTIM)was used to describe the complex microstructure transitions.It is demonstrated that the amorphous structures are mainly formed with the three bond-types of 1551,1541 and 1431 in the system,and the icosahedral cluster(12 0 12 0)and other basic polyhedron clusters of(12 2 8 2),(13 1 10 2),(13 3 6 4),(14 1 10 3),(14 2 8 4)and(14 3 6 5)play a critical and leading role in the transition from liquid to glass.The nano-clusters formed in the system consist of some basic clusters and middle cluster configurations by connecting to each other,and distinguish from those obtained by gaseous deposition and ionic spray.From the results of structural parameter pair distribution function g(r),bond-types and basic cluster-types,it is found that the glass transition temperature Tg for liquid metal Cu is about 673 K at the cooling rate of 1.0×1014 K/s.
文摘A multi-component Cu-based metal powder was chosen for direct laser sintering. The powder consists of a mixture of high-purity Cu powder, pre-alloyed CuSn and CuP powder. Liquid phase sintering with complete melting of the binder (CuSn) but non-melting of the cores of structural metal (Cu) proves to be a feasible mechanism for laser sintering of this powder system. The microstructural evolution of the sintered powder with variation of laser processing parameters was presented. High sintering activities and sound densification response were obtained by optimizing the laser powers and scan speeds. Using a high laser power accompanied by a high scan speed gives rise to balling effect. At a high laser power with a slow scan speed the sintering mechanism may change into complete melting/solidification, which decreases the obtainable sintered density. The role of additive phosphorus in the laser sintering process is addressed. Phosphorus can act as a fluxing agent and has a preferential reaction with oxygen to form phosphatic slag, protecting the Cu particles from oxidation. The phosphatic slag shows a concentration along grain boundaries due to its light mass as well as the short thermal cycle of SLS.
文摘分别采用Cu箔和Cu膜作为中间层,在853 K保温情况下进行了S iC颗粒增强铝基复合材料的瞬间液相扩散连接试验.用金相显微镜、扫描电镜、能谱仪、X射线衍射仪和拉伸试验机研究了表面状态、保温时间和压力对接头显微组织和性能的影响.结果表明:合适的压力和中间层厚度能有效改善接头的组织和力学性能,接头剪切强度随保温时间延长而提高.表面状态对接头强度有较大影响.采用Cu膜作中间层由于没有氧化膜的影响,可以获得更好的接头性能,在加2 M Pa压力,853 K保温120 m in连接时接头剪切强度可达169.1 M Pa,约为母材强度的81.7%.
