Dissolution of Al2Cu phase in non-modified and Sr modified 319 type alloys

This study investigates the effects of solution heat treatment on dissolution of the Al2Cu phase in non-modified and 150 ppm Sr modified 319 type alloys. Experimental and industrial 319 alloys containing different Mg levels (0, 0.3 and 0.6 wt-%) were used for this purpose. Electron probe microanalysis (EPMA) in conjunction with energy dispersive X-ray (EDX) analysis was used to monitor the distribution of Cu in the matrix and to measure the undissolved Al2Cu phase. In as cast 319 alloys, copper segregates at the dendrite boundaries. The addition of Mg and Sr may cause this segregation to deteriorate. After heat treatment, the copper begins to distribute more evenly across the dendrite as well as in the matrix. The amount of Cu dissolved in the matrix increases with increasing solution time and temperatures, reaching a maximum for the 490 degrees C/8 h solution heat treatment. The dissolution process of eutectic and block like Al2Cu was also investigated.