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He P.,Harbin Institute of Technology | Lu X.-C.,Harbin Institute of Technology | Lin T.-S.,Harbin Institute of Technology | Li H.-X.,Harbin Institute of Technology | And 6 more authors.
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2012

Carbon nanotubes (CNTs) reinforced Sn-58Bi composites were successfully fabricated through ball-milling method and low temperature melting process. The influence of multi-walled carbon nanotubes (MWCNTs) on the mechanical strength and ductility of Sn-58Bi lead-free alloy was studied. The mechanical test results show that the bending strength of Sn-58Bi-0.03CNTs (mass fraction, %) composite is increased by 10.5% than that of the Sn-58Bi alloy, which can be attributed to the reduction of Sn-rich segregation and the grain refinement. The toughness of Sn-58Bi-0.03CNTs composite is increased by 48.9% than that of the matrix materials. It is indicated that the influence of CNTs on the strength of Sn-58Bi-xCNTs composite is insignificant. In addition, the fracture mechanism of CNTs reinforced Sn-Bi composite was analyzed. The corresponding fracture surface comparison between the Sn-58Bi-0.03CNTs composite and the monolithic Sn-58Bi alloy was made to identify the influence of CNTs on the fracture behavior and the reinforcing effect of CNTs. © 2012 The Nonferrous Metals Society of China.

Yang M.,Harbin Institute of Technology | Cao Y.,Harbin Institute of Technology | Joo S.,Harbin Institute of Technology | Joo S.,Korea Advanced Institute of Science and Technology | And 3 more authors.
Journal of Alloys and Compounds | Year: 2014

A study was performed on the precipitation behavior of Cu 6Sn5 during the solidification of Sn-based solders/ Cu joints and its effect on the growth of interfacial intermetallic compounds (IMCs). During cooling, Cu in molten solder precipitates in the form of Cu 6Sn5 both within the solder matrix and at the interface. The precipitation at the interface can greatly affect the interfacial IMC morphology and thickness but cannot change the interfacial IMC orientation. In general, additional Cu6Sn5 will precipitate at the solder/Cu interface when the Cu content is increased in the molten solder during soldering and when the cooling rate decreases during solder solidification. If the Cu content in the molten solder is sufficiently high, during cooling, the precipitated Cu6Sn5 will develop a prismatic morphology with the exposed surface indexed as (10-10) along the [0001] direction of the existing Cu6Sn5 grains at the interface. © 2013 Elsevier B.V. All rights reserved.

Lu X.-C.,Harbin Institute of Technology | He P.,Harbin Institute of Technology | Zhang B.-B.,ZTE Corporation | Ma X.,Yik Shing Tat Industrial Company Ltd | Qian Y.-Y.,Harbin Institute of Technology
Cailiao Gongcheng/Journal of Materials Engineering | Year: 2010

Effects of different solidification modes, including of furnace cooling, air cooling, water cooling and liquid nitrogen cooling, and magnetic fields on the impact toughness and microstructure of Sn-Bi solders are studied. The results show that fast cooling and rotating magnetic fields were applied for refining the structure of the Sn-Bi solder. Although these technologies can refine the grain size, meanwhile they reduced the plasticity of the solder. For Sn-57Bi alloy fast cooling caused the segregation of Bi, and the rotating magnetic field lead to the structural heterogeneity. Both methods destroyed the strengthening mechanism of adding Ge and lead the Ag3Sn phase to become coarse. Further more, the centrifugal force of the rotating magnetic of the 43Sn-Bi-3.5Ag caused the increase of segregation. With the cooling rate increases, the toughness of Sn-57Bi eutectic solder increase firstly and then decrease due to the joint actions of structure refinement and segregation.

He P.,Harbin Institute of Technology | Lu X.-C.,Harbin Institute of Technology | Zhang B.-B.,ZTE Corporation | Ma X.,Yik Shing Tat Industrial Company Ltd | Qian Y.-Y.,Harbin Institute of Technology
Cailiao Gongcheng/Journal of Materials Engineering | Year: 2010

The effect of Ag, Ge, Cu, Sb, Zn, Ce, P and Ni inclusions on melting temperature, wettability, impact toughness and microstructure of 43Sn-57Bi lead-free solders were investigated. The result showed that those inclusions had little influence on melting temperature of the solders. Addition of P, Ni resulted in the appearance of Bi, which decreased the performance of solders. Ag3Sn and zinc rich phase could increase the performance when the shape was appropriate. Add Ag, Ge, Zn, Cu solely could improve the solder's ductility, while Sb, Ce, P, Ni could decrease the ductility. Yield strength of the solders and shear strength of the joint could improve with the addition of Ag, Ge. The improvement effort of 43Sn-Bi-1Ge-1Ag was the best in the solders with several inclusions.

Yang M.,Harbin Institute of Technology | Ma X.,Yik Shing Tat Industrial Company Ltd | Li M.-Y.,Harbin Institute of Technology
Advanced Materials Research | Year: 2014

The coarsening behavior of Cu6Sn5 grains formed at the Sn37Pb/Polycrystalline Cu interface is investigated in terms of their orientation evolution during solid-state aging. The results show that the coarsening behavior of the interfacial Cu6Sn5 grains during solid-state aging are quite different from that during liquid-state soldering. The occurrence of the coarsening in the solid-sate reaction is caused by the different surface energies between two adjacent grains. In addition, the texture morphologies of the interfacial grains affect their coarsening rates. In particular, the interfacial Cu6Sn5 grains formed at 200 °C exhibit a texture with the [0001] direction normal to the interface after 16 days of aging at 150 °C, and the formation of this texture accelerates the coarsening process of the interfacial Cu6Sn5 grains. © (2014) Trans Tech Publications, Switzerland.

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