Size and orientation dependent mechanical behavior of body-centered tetragonal Sn at 0.6 of the melting temperature

• Published in: Acta materialia 2016-08, Vol.115, p.76-82
• Main Authors: Philippi, Bastian, Kirchlechner, Christoph, Micha, Jean Sébastien, Dehm, Gerhard
• Format: Article
• Language: English
• Subjects: Activation; BCC metals; Dislocations; Lead-free solder; Mechanical properties; Melting; Micromechanics; Orientation; Plasticity; Size-effect; Slip; Synchrotron diffraction; Tin
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2016.05.055

Although, tin is one of the most prominent metals in soldering, very little is known about its mechanical behavior. In addition, possible size-effects of tin can become restricting for the ongoing miniaturization of microelectronic devices. Due to the low melting temperature of 505.15 K and the body-centered tetragonal crystal structure, differences in the mechanical behavior compared to face-centered cubic and body-centered cubic metals can be expected. Since Tin is especially interesting because of its multiple different slip systems, post mortem slip step analysis allowed to determine the activated slip systems and thus, to calculate size dependent critical resolved shear stresses. The measured size scaling exponent (−1.07 ± 0.06) is close to model-predictions of −1, irrespective of the activated families of slip systems in different orientations. Furthermore, an exceptional low scatter of the flow stress in various samples and no apparent hardening is found. It is concluded, that the activation of dislocation sources instead of dislocation-dislocation interactions are responsible for the observed behavior. This is in line with complementary μLaue diffraction experiments which indicate an unresolvable low density of geometrical necessary dislocations. [Display omitted]