The present study attempted to assess the corrosion performance of iron (Fe) and bismuth (Bi) added Sn-1Ag-0.5Cu (SAC105) lead-free solder alloy in NaCl-based solutions. Potentiodynamic polarisation measurements indicated that in acidic or alkaline solutions, corrosion potential (Ecorr) shifted to more negative (active) values and the corrosion current density (icorr) visibly increased. In a neutral pH solution, SAC105 solder alloys exhibited notable corrosion resistance owing to the stability of passive film formed on the surface of solder alloys. Potentiodynamic polarisation curves also showed that the addition of 0.05 wt% Fe and 1 wt% Bi improved the corrosion rate of SAC105 and lowered the Ecorr towards more noble value due to the reduced micro-galvanic interaction between the cathodic Ag3Sn IMCs and the anodic Sn matrix. Immersion tests revealed that the mass loss increased in the order: SAC105-Fe-2Bi > SAC105 > SAC105-Fe-1Bi.
Purpose
– The purpose of this paper is to analyze the effect of lanthanum (La) doping on the microstructure and mechanical properties of tin-silver-copper (SAC) alloys and to find out an optimum La doping concentration upon which the best set of the desirable properties can be possible. SAC tertiary Pb-free solders are thought to be the best substitutes for Pb-based solders but have limitations due to their coarse microstructure.
Design/methodology/approach
– Three samples with varied La concentrations were synthesized from pure metals. SAC with various concentrations of doped La were studied in detail. Scanning electron microscopy images were studied and were further analyzed by the ImageJ software to measure the average intermetallic compounds (IMCs) size. Optical microscopy was used to study the grains. MTS tensile machine was used determine out the mechanical properties. All the analysis was done before and after thermal aging. Finally, an optimum La doping concentration was found.
Findings
– By doping a suitable concentration of La in SAC, the average IMCs size as well as grain size was greatly reduced. Yield stress and tensile strength were quite improved as a result. Unlike previous studies, ductility was not lowered. Impact toughness was seen to be significantly improved. Finally, an optimum La doping concentration was found to be 0.3 per cent by weight, as beyond this, ductility drops rapidly.
Originality/value
– The optimum La doping concentration in SAC resulted in a much refined microstructure and a very good set of the desirable properties, including yield stress, tensile strength, ductility, impact toughness and expectedly creep and fatigue resistances, for the first time.
Between the Masjid-i Jāmiᶜ and the Maydān-i Shāh was a distance of several kilometers, dotted by minarets, mausoleums, mosques and bazaar areas which served the trade of the central plateau of Persia. They had been built over the intervening centuries since Sasanian times, the old town gradually expanding, some of the small clusters of the bazaar still remaining as satellite villages under Shāh ᶜAbbās’ reign. It was his genius which formed the new city, and it was his conception that linked the new with the old.Today, the least known to the visitor but in many ways quite the most fascinating aspect of Isfahan is the region that lies between the great mosques: the bazaar. Built by Shāh ᶜAbbās, the entrance to the bazaar, the Qaysariyah, stands at the center of the north end of the Maydān-i Shāh. Set back from the main plaza in a fivesided recess, it forms a courtyard which once embraced a large pool.
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