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The microstructure and mechanical properties of Sn-0.7Cu solder alloy and Sn-0.7Cu with 1.0–5.0 wt% indium addition were investigated in this study. With indium added into Sn-0.7Cu solder, the melting temperature decreased and the reaction temperature increased. Coarse grains of Cu 6 (Sn,In) 5 intermetallic compounds (IMCs) were formed in the alloy matrix when the indium content increased to 1.0 wt%. Indium was evenly distributed in the β-Sn phase and Cu 6 (Sn,In) 5 IMCs in as-prepared In-containing solder alloys. After isothermal aging, indium accumulated gradually in the Cu 6 (Sn,In) 5 IMCs while decreasing its content in the β-Sn phase. Tensile test results indicated that the ultimate tensile strength increased obviously and that the elongation decreased significantly with indium addition. Sawtooths were observed in the stress-strain curves of all aged In-containing alloys. A model describing a coherent relationship between the β-Sn phase and the Cu 6 (Sn,In) 5 phase was proposed to explain this phenomenon. The fracture surface of the Sn-0.7Cu alloy exhibited a ductile fracture mode while a mixed ductile-brittle fracture mode occurred when excessive indium was added into Sn-0.7Cu alloys. [ABSTRACT FROM AUTHOR]

In this study, the effects of factors such as temperature, solution and surface roughness on the growth of whiskers in a 100 μm thick Sn-Al alloy coating were comparatively investigated under different environments. The results indicated that whiskers did not grow after nucleation at 30 °C in oil. With the increase in aging temperature, whiskers started to grow after nucleation. The morphologies of whiskers showed the filament-type at 50 °C and the hillock-type at 100 °C. The residual compressive stress in the coating gradually decreased with the growth of whiskers and hillocks. Whisker nucleation was not found on the coating kept in water solution. The residual stress in the coating was rapidly released through the micro-cracks at the coating/substrate interface instead of growing whiskers. The oxide layer on the coatings with rough surfaces was easier to crack due to the higher thermal stress. The thermal stress on the oxide layer was in directly proportional to the depth of indentation and inversely proportional to the grain size. Whiskers preferentially grew on the (001)-oriented Sn grains in the coating. The finite element simulation results indicated that the grains with c -axis perpendicular to the coating surface had higher thermal strain and tended to grow whiskers. During creep deformation, the stress exponent increased from 7.0 to 11.5 with the increase in temperature. The mechanism for whisker growth was dislocation slip. Grain boundaries were observed in the hillocks. The power-law breakdown was the mechanism for the growth of hillocks. Image 1 • Environments affect the morphologies of whiskers. • Whiskers prefer to grow from the (001)-oriented grains in the normal direction. • A model is proposed to calculate the thermal stress on the Sn oxidation. • Grain boundaries sliding is observed in the hillocks. [ABSTRACT FROM AUTHOR]

In this study, the effect of adding trace Er element on the microstructure and mechanical properties of AA6061 twin-roll casting sheet was evaluated. An NF6–300 vertical twin-roll cast-rolling mill was used to prepare AA6061 twin-roll casting sheet with different Er contents, and the main phase morphology and formation mechanism of Er in the alloy were analyzed using microstructure observation, scanning electron microscopy, transmission electron microscopy, and other microstructure analysis techniques. The results show that the addition of a small amount of Er can form the primary Al 3 Er phase in the alloy. This phase structure becomes an excellent heterogeneous nucleation core of α-Al. This significantly affects the grain size of AA6061 TRC sheets. In addition, Er interacts with the Fe in the TRC sheet. Therefore, the iron-rich phase in the structure changes from coarse needle-like and skeletal shapes to smaller short rods and blocks, and micron-sized spheroids or lumps appear in the structure. Spheroid-like iron-rich phase contains Er. When the amount of Er addition exceeds 0.4 wt%, the number of rare-earth compounds and impurity phases in the structure increases significantly, and they mainly precipitate along the grain boundaries. This increases the strengthening effect of second phase and greatly reduces the plasticity of the material. When the amount of Er addition reaches 0.4 wt%, the comprehensive mechanical properties of TRC sheet are the best. At this time, the tensile strength, yield strength, and elongation are 160.14 MPa, 124.77 MPa, and 10.68%, respectively. • Effect of Er element on the microstructure and mechanical properties of twin-roll casting 6061 Al alloy sheet. • Er can form the primary Al3Er phase, which is an excellent heterogeneous nucleation core. • Er promote the transformation of Fe phase, and form micron-sized spheroids -like iron-rich phase contains Er. [ABSTRACT FROM AUTHOR]

AA6061 twin roll casting plate was annealed and then the hot rolling experiment was carried. Effect of Mn content on microstructure evolution and recrystallization behavior was investigated. The results show that Mn element can significantly change the recrystallization behavior of the alloy and produce particle induced recrystallization (PSN) effect. The mechanical properties of the plate would be effectively improved with appropriate Mn content. With the increase of Mn content in cast rolling plate, the number of recrystallized grains in the alloy increases; The strength and hardness of 6061 cast rolled plate increases first and then decreases with the increase of Mn content in the alloy, and the elongation decreases gradually with the increase of Mn content. Comprehensively considered, when the Mn content is 0.46%, the mechanical properties of the plate are optimal, i.e., tensile strength 197.36 MPa, yield strength 157.89 MPa and elongation 6.23% respectively. [ABSTRACT FROM AUTHOR]