Microstructure, Mechanical Properties and Corrosion Behaviors of Al–Li–Cu–Mg–Ag–Zn Alloys

Combined with microstructure characterization and properties tests, the effects of Zn contents on the mechanical properties, corrosion behaviors, and microstructural evolution of extruded Al–Li–Cu–Mg–Ag alloys were investigated. The results show that the increase in Zn contents can accelerate hardening kinetics and improve the hardness of peak-aged alloys. The Zn-added alloys present non-recrystallization characteristics combined with partially small recrystallized grains along the grain boundaries, while the T1 phase with finer dimension and higher number density could explain the constantly increasing tensile strength. In addition, increasing Zn contents led to a lower corrosion current density and a shallower maximum intergranular corrosion depth, thus improving the corrosion resistance of the alloys. Zn addition, distributed in the central layer of T1 phases, not only facilitates the precipitation of more T1 phases but also reduces the corrosion potential difference between the T1 phase and the matrix. Therefore, adding 0.57 wt.% Zn to the alloy has an excellent combination of tensile strength and corrosion resistance. The properties induced by Zn under the T8 temper (solid solution treatment + water quenching + 5% pre-strain+ isothermal aging), however, are not as apparent as the T6 temper (solid solution treatment + water quenching + isothermal aging).

Microstructural Evolution and Electrochemical Behavior of Solution Treated, Hot Rolled and Aged MgDyZnZr Alloy

In order to develop a potential route to fabricate plates and clips for orthopedic applications, a Mg–3.4Dy–0.2Zn–0.4Zr (wt.%) alloy was produced and analyzed in different conditions: solution treated at 525 °C for 3 h, hot rolled and hot rolled and aged at 250 °C. The aging behavior of the rolled alloy was investigated during isothermal aging at 250 °C, and a significant peak was observed at 10 h. The electrochemical behavior was evaluated in 0.9 wt.% NaCl solution at 37 ± 0.5 °C by potentiodynamic polarization and electrochemical impedance spectroscopy. The 525 °C-3 h and hot rolled specimens exhibited corrosion rates of 2.0 and 1.7 mm/year, respectively. The hot rolled and aged at 250 °C for 10 h specimen presented a grain size of 11.8 ± 1.7 μm with an intense macrotexture of the basal {0002} plane, hardness of 73 ± 3 HV and higher impedance modulus and obtained the highest corrosion resistance with a corrosion rate of 0.9 mm/year.

Mechanical Properties of Doped Solder SAC-Q for High Strain Rate Testing at Extreme Surrounding Temperatures for 6 Months of Isothermal Aging

Electronic parts may often get exposed to high strains during shocks, vibrations and drop conditions in both commercial and defense applications. In addition, such electronic parts can often be simultaneously exposed to extreme surrounding temperatures between −65°C and 200°C after storage in non-climate-controlled conditions. Electronic equipment can be subjected to strain rates of 1 to 100 per second in shock and vibration. Many of the doped SAC soldering alloys in the electronic components, including SAC-Q, SAC-R, Innolot have found applications in long-term thermal exposure environments. Low temperature high strain-rate properties are needed to assure durability under high temperature storage followed by shock and vibration. There is scarcity of high strain-rate data on alloys exposed to high temperature aging operating at extreme low-temperatures and extremely-high temperatures. For this study, SAC-Q material was tested and analyzed at temperatures from −65°C to 200°C and at a strain rates of from 10 to 75 per second. Following the production and retrieval of the specimens, specimens were stored for isothermal aging for up to 6 months at 100°C temperature, before performing tensile test experiments at various operating temperatures. Stress vs strain curves are formed for the wide range of strain rates and surrounding temperatures. In addition, test results and data were complemented by the Anand viscoplasticity model and by calculating stress-strain behavior, evaluated in a wide range of working temperatures and strains rates.