Unveiling the densification and superelasticity mechanisms of sintered NiTi nanoparticles: Role of sintering pressure and temperature

Molecular dynamics simulations were employed to establish multi-size and multi-particle NiTi nanoparticle models to investigate the effects of different sintering pressures (50 MPa, 200 MPa, 500 MPa, and 800 MPa) and sintering temperatures (900 K, 1050 K, and 1200 K) on densification behavior and superelasticity. The results show that the melting point of NiTi nanoparticles exhibits a pronounced size dependence. As the particle size increases from 6 nm to 8 nm and 10 nm, the melting point increases from 1590 K to 1625 K and 1700 K, respectively. With increasing sintering pressure or sintering temperature, atomic diffusion between particles is enhanced, the sintering density gradually increases, and interconnected pores gradually transform into isolated pores, thereby promoting neck growth and densification during sintering. Tensile loading-unloading results indicate that higher sintering pressure or sintering temperature corresponds to higher peak stress and lower residual strain, resulting in better superelastic recovery behavior. This is mainly attributed to pore reduction, enhanced particle bonding, and more continuous stress transfer paths. This study reveals the influence of sintering pressure and sintering temperature on the densification and superelastic behavior of NiTi nanoparticles at the atomic scale, which can provide insight into the microscopic mechanisms during the sintering process of NiTi nanoparticles.