Mechanical Reliability of Reactively Alloyed NiAl as a Structural Material

Abstract

In this study, for the practical use of reactively alloyed NiAl as a structural material, its mechanical reliability is evaluated. An Al/Ni multilayer film is attractive as a local heat source for soldering. To investigate the difference in mechanical characteristics between as-deposited Al/ Ni multilayer films and reactively alloyed NiAl films, quasistatic uniaxial tensile tests and stress relaxation tests were conducted. A higher Young's modulus and a higher strength were obtained in the NiAl films. The films also showed better consistency under a constant applied strain. Then, four-point bending tests were carried out to examine the fracture strength of reactively bonded solder joints and to specify the fracture origin. All the joints fractured at the interface of the SnAg solder layer and the reactively alloyed NiAl layer. The durability of the reactively alloyed NiAl in the joints is discussed in the light of the grain size evaluated by electron backscatter diffraction (EBSD) analysis.