Mössbauer and magnetic characterization of joints of steel pieces in transient liquid phase bonding experiences

DI LUOZZO N.; MARTÍNEZ STENGER P. F.; CANAL J. P.; FONTANA M.; ARCONDO B.

Lima

Conferencia; Latin American Conference on the Applications of the Mössbauer (LACAME 2010); 2010

Universidad Nacional Mayor de San Marcos

In recent years, the transient liquid phase bonding (TLPB) process has been widely studied in order to improve the characteristics of the joints by means of composition and microstructure homogenization along the joined pieces. Joining of seamless, low carbon, steel tubes were performed by means of a TLPB process employing a foil of Fe-Si-B metallic glass as filling material. An annulus was cut from the foil whose dimensions were diameter = diameter of the tube and thickness = 20µm. The experiences were performed by induction heating under a moderate pressure and argon flux. Thermal cycles consisted on a fast heating up to temperature T (TM < T < TT with TM and TT the melting temperature of the metallic glass and the tube materials respectively) then, an isothermal stage for a time t and finally a controlled cooling down to room temperature. The influence of the different parameters was evaluated. As usually, the microstructure of the joint zones was analyzed employing optical and scanning electron microscopy. On the other hand, small powder samples were obtained from different points along the joined tubes: joint zone, heat affected zone and base material. The sampling was performed both in pieces successfully welded and in those which experienced failures. These samples were analyzed employing Mössbauer effect spectroscopy and AC-magnetization measurements. Virgin and crystallized Fe-Si-B metallic glasses were also analyzed. The results obtained are correlated with the diffusion of the elements (Si, B) during the process and the microstructure obtained.