The Initial Reactions and Microstructures of the Cu-Sn, Au-Sn and Fe-Al Interfaces

Autor: Kuang-kuo Wang, 王光國
Rok vydání: 2009
Druh dokumentu: 學位論文 ; thesis
Popis: 98
The microstructure of η''-Cu6Sn5 during in the early stage of growth was studied. Sn was electroplated onto thin Cu foil at room temperature and the specimen was annealed at 150 ºC for 30 s. The Cu and Sn on the η''-Cu6Sn5 surfaces were removed electrolytically and the specimens were analyzed with scanning and transmission electron microscopes. The η''-Cu6Sn5 grains on the Cu side were as small as 5 nm but grew rapidly to 0.3 to 0.5 μm on the Sn side. The orientation relationships between η''-Cu6Sn5 and Cu were studied by a thin film technique. Cu was evaporated onto the NaCl (001) and (111) surfaces to form epitaxial Cu thin films and Sn was then evaporated onto the Cu films to form η''-Cu6Sn5. Two types of orientation relationships were found, i.e., (1) [204]η''//[001]Cu (zone axis), (40-2)η''//(110)Cu, and (020)η''//(1-10)Cu, and (2) [204]η''//[111]Cu (zone axis), (40-2)η''// Cu, and (020)η''//(-1-12)Cu. The interfaces were analyzed. (Chapter 1) A very thin η-Cu6Sn5 layer was formed by dipping thin Cu foil into molten Sn at 240 ºC for 1 second and quenching in ice water. The Sn and Cu on the η-Cu6Sn5 surface were removed electrolytically to study the surface morphologies. The η-Cu6Sn5 grains on the Sn side had a worm-type shape, about 0.3-0.5 μm wide and up to 2 μm long, but those on the Cu side were very small, about 5 nm in size. The nucleation and growth of the η-Cu6Sn5 grains were discussed. The orientation relationships between η-Cu6Sn5 and Cu were determined by transmission electron microscopy. The (11-20) plane of η-Cu6Sn5 was found to be the interface with both the Cu (001) and (-111) surfaces, and a common orientation relationship of (0001)η//(110)Cu was observed. The match of atoms between η-Cu6Sn5 and Cu on the above interfaces were analyzed. (Chapter 2) A thin film technique was developed to study the orientation relationship and interface between ε-Cu3Sn and Cu by transmission electron microscopy. Epitaxial Cu thin films were grown on the NaCl (001) and (111) surfaces and Sn was evaporated to form ε-Cu3Sn directly without breaking the vacuum. The orientation relationship Z=[001]ε//[111]Cu, (100) ε //(-110)Cu, and (010)ε //(-1-12)Cu was found on the Cu (111) surface, but none on the Cu (001) surface. The interface was analyzed. (Chapter 3) The formation of the Fe-Al inhibition layer in hot-dip galvanizing is a confusing issue for a long time. This work presents a characterization result on the inhibition layer formed on a TiNb-stabilized interstitial-free steel after a short time galvanizing. The Fe-Al and steel interface was free from oxide, so that the Fe-Al intermetallic compound could directly nucleate on ferrite grains. TEM electron diffraction showed that only Fe2Al5 was formed and it had a well-defined orientation relationship of [110]FA// [111]Fe, (001)FA//(0-11)Fe and (1-10)FA//(2-1-1)Fe with Fe substrate where FA stands for Fe2Al5. The interfaces between Fe2Al5 and Fe are discussed. The Fe2Al5 grains nucleated epitaxially on Fe substrate had very small grain size, 20 nm or less, and several variants were intimately mixed. The grains grew rapidly to hundreds of nanometers toward the Zn side. (Chapter 4) The orientation relationships and interfaces of δ-AuSn with the Au (001), (110) and (111) surfaces were studied with transmission electron microscopy. Au was evaporated onto the NaCl (001), (011) and (111) surfaces to form epitaxial Au thin films and Sn was evaporated onto the Au film to form δ-AuSn. Two types of orientation relationships were found: (1) (11-20)δ//(001)Au, (0001)δ//(110)Au, and (1-100)δ//(-110)Au, which was found on the (11-20)δ/(001)Au and the(1-100)δ/(-110)Au interfaces; and (2) (11-20)δ//(-111)Au, (0001)δ//(110)Au, and (1-100)δ//(-11-2)Au, which was found on the (11-20)δ/(-111)Au interface. The interfaces were analyzed by the structures of the surfaces and the orientation relationships. The nucleation of δ-AuSn on these interfaces was also discussed. (Chapter 5)
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