Effect of alloying on mechanical and electrical properties of ZINC-based high temperature solders

Abstract

In this research the bulk solder properties of Zn-Al and Zn-Ni systems are explored systematically. Different percentage of Al (i.e. 3, 5 and 7 wt.%) and Ni (i.e. 0.2, 0.3 and 0.4 wt.%) were alloyed with Zn separately and compared with as cast Zn samples. Compositional, thermal, microstructural, mechanical and electrical properties of these alloys are analyzed and compared accordingly. DTA analysis revealed that the addition of Al and Ni in Zn caused to reduce the melting temperature of Zn to 379 OC and 415OC respectively. Microstructures of Zn-Al (AZ) alloys with different percentages of Al, exactly resembles to the Zn-Al binary phase diagram. In the microstructures of Zn-0.2Ni (2NZ), Zn-0.3Ni (3NZ) and Zn-0.4Ni (4NZ) alloys, the evidence of Zn grains in eutectic matrix, particles at the grain boundaries of Zn and δ-phase grains in Zn are observed respectively. EDX analysis of AZ samples revealed the existence of both α' and α phase in the microstructures. In the case of Zn-Ni alloys, EDX results confirmed the presence of δ-phase. Both Al and Ni addition caused to increase the UTS and fracture strain of Zn. 5AZ sample has the highest UTS and fracture strain with dimpled of fracture surface. It was also found that the separate addition of Al and Ni caused to increase the hardness of Zn. The 5 wt.% Al added sample is the hardest amongst the Zn-Al alloys with hundred percent of lamellar structure. Thermal mechanical analysis (TMA) of the samples revealed that with increasing the amount of Al content in Zn- Al solders and Ni in Zn-Ni solders results in the reduction of CTE. The CTE of the β phase is higher than α phase. Increasing the amount of Al from 3 to 7 wt.%, electrical conductivity of the Zn based alloys also gradually increases. The resistivity β phase is higher than pure Zn phase, which has relatively higher resistivity than α phase. Electrical resistivity of NZ samples are slightly higher compared to the Zn sample. The lowest resistivity of 6.22 μΩ.cm was found in the 7AZ sample.