3. Results and Discussion
3.1 Microstructure of resistance spot weld for
Al/steel The microstructure of the aluminum/steel weld
is presented in Fig. 2. Pores and gaps are often observed at the steel/aluminum interface. The presence of the weld discontinuities along the aluminum/steel interface can be attributed to the shrinkage stresses. During weld, the aluminum adjacent to
the aluminum/steel interface is the last area to solidify. Shrinkage stresses combined with constraint from the adjacent solid metal can result in voids (as marked in Fig. 2(a)), typically demonstrated as pores (adjacent to the steel) and solidification cracks