Portevin-LeChatelier effect of Al-7 mass%Si-Mg cast alloys

The Portevin-LeChatelier effect of three Al-7Si-Mg cast alloys with 0.11, 0.26 and 0.46 mass% magnesium was compared with that of an Al-7 mass%Si cast alloy. Part of the test alloys were solution treated at 813 K and the remaining were aged at 273 K and were tension tested. The critical strain for the onset of flow instability could be raised by increasing the magnesium content. For solution-treated specimens tested at low temperatures, results show that critical strain decreases with temperature. For those tested at high temperatures, there occurs an aging effect which is more pronounced with increasing magnesium content and temperature. For specimens pre-aged at 273 K, the critical strain increases with aging time.