  In recent years, lead-free solder alloys based on tin, silver, or copper have
gained popularity over lead-based solder alloys due to their improved
mechanical and electrical properties and their non-toxic nature. In our
previous studies, we examined the stress-strain behavior of SAC305 under
varying cooling rates. This study extends our investigation to various
lead-free solder materials, including Sn, Sn-Ag, and SAC305, to compare their
relative mechanical and cyclic properties. We employed molecular dynamics to
model the atomistic behavior. Initially, the models were melted at a constant
rate and then cooled at various rates, including 2.5 K/ps, 10 K/ps, 50 K/ps,
and 100 K/ps. Additionally, exponential cooling was used to replicate
real-world cooling scenarios.. We utilized a set of modified embedded atomic
model (MEAM) interatomic potentials for the tensile test and cyclic loading.
The tensile test has been conducted until fracture occurs at a constant strain
rate. Furthermore, we investigated the cyclic loading behavior within a strain
range of -10% to 10% for 10 cycles. The results indicated that cooling rates
significantly influenced mechanical properties, with slower rates (2.5 K/ps and
10 K/ps) showing substantial differences, while the differences between higher
rates (50 K/ps and 100 K/ps) were less pronounced. The ultimate strength,
Young's modulus, modulus of resilience, and coefficient of thermal expansion
exhibited a negative correlation with increasing cooling rates, while the
modulus of toughness increased, indicating improved impact resistance. To
assess energy dissipation during cyclic loading, we examined the hysteresis
loop area and stress amplitude. After a certain number of cycles, the energy
lost during each cycle reached a stable level.
