EPMA Analysis

EPMA analysis also accomplished for joint type B and is presented in Figure 13. This elemental map analysis on joint type B indicated high levels of Mg at the interface and smaller levels of Cu and Al. The elemental map of Zn (not presented here) included a uniform distribution of it in all areas as a low percentage trace element.

**Figure 13.** EPMA analysis on joint type B (1100 J) interface: Map of Mg, Cu and Al.

Two main regions are recognizable while looking at three elemental EPMA maps in Figure 13, and comparing them with SEM-EPMA interface photo. The main region is an area around the interface, wherein maps of Mg and Cu exhibit good overlapping together. Mg is prevalent in this region, and Cu is in a lower concentration that predicts a composition rich in Mg with lower content of Cu. As it was explained before, there are two main compositions in the binary phase diagram of Mg-Cu, including Mg2Cu and MgCu2. Keeping this in mind, it should be again noticed that the maximum interface temperature obtained for this joint was 518 ◦C (see Figure 7), which is over *Teu* of Mg2Cu and lower than that for MgCu2, hence it can be suggested that the main area around the interface is composed of Mg2Cu intermetallic compound.

Another interfacial region recognized in the centerline of the interface, consisted of a composition containing Al, Mg, and Cu. It seems that the resolution of EPMA analysis is not enough to identify the reaction product in the centerline. Therefore, TEM analysis also done on this region.
