Study of mechanical properties of indium-based solder alloys for cryogenic applications

Purpose This study aims to develop indium-based solders for cryogenic applications. Design/methodology/approach This paper aims to investigate mechanical properties of indium-based solder formulations at room temperature (RT, 27 degrees C) as well as at cryogenic temperature (CT, -196 degrees C) and subsequently to find out their suitability for cryogenic applications. After developing these alloys, mechanical properties such as tensile and impact strength were measured as per American Society for Testing and Materials standards at RT and at CT. Charpy impact test results were used to find out ductile to brittle transition temperature (DBTT). These properties were also evaluated after thermal cycling (TC) to find out effect of thermal stress. Scanning electron microscope analysis was performed to understand fracture mechanism. Results indicate that amongst the solder alloys that have been studied in this work, In-34Bi solder alloy has the best all-round mechanical properties at RT, CT and after TC. Findings It can be concluded from the results of this work that In-34Bi solder alloy has best all-round mechanical properties at RT, CT and after TC and therefore is the most appropriate solder alloy amongst the alloys that have been studied in this work for cryogenic applications Originality/value DBTT of indium-based solder alloys has not been found out in the work done so far in this category. DBTT is necessary to decide safe working temperature range of the alloy. Also the effect of TC, which is one of the major reasons of failure, was not studied so far. These parameters are studied in this work.