Multiaxial creep behaviour of Indalloy 227 [soldering]

Indalloy 227 (76% Sn/20% In/3% Ag) lead-free solder was investigated. Constant load creep tests were performed for a variety of temperatures and initial stresses to find the behaviour at very low strain rates. The data was collapsed into a single reduced time curve which predicts the steady state creep rate for the material at any combination of tensile loading and temperature. From this data, a multiaxial creep deformation model was developed by defining an effective stress via the von Mises yield criterion. The corresponding effective strain along with the effective stress from the multiaxial loading can be used in the reduced time model to predict creep behaviour for any loading. A combined tension-torsion loading test was devised to verify the three-dimensional model for a variety of multiaxial loadings.