Cast Shop Technology: Grain Refining and Solidification
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee
Program Organizers: David Gildemeister, Arconic Technology Center
Wednesday 2:00 PM
March 1, 2017
Location: San Diego Convention Ctr
Session Chair: Stephen Instone, Hydro Aluminium Rolled Products GmbH
2:00 PM Introductory Comments
Effect of Ultrasonic Processing on a Direct Chill Cast AA6082 Aluminium Alloy: Georges Salloum-Abou-Jaoude1; Dmitry Eskin1; Carla Barbatti2; Philippe Jarry2; Martin Jarrett2; Zhongyun Fan1; 1Brunel University London; 2Constellium
For many years now, ultrasonic melt treatment (UST) has proven itself to promote grain refinement in aluminium alloys. The current work presents cavitation-aided grain refinement obtained on commercial AA6082 DC-cast billets. Grain refinement was achieved while applying UST in the crucible away from the sump, prior to casting. Since in high strength alloys, Zr and Ti are commonly present as alloying elements for anti-recrystallization and corrosion resistance properties, their as well as UST parameters influence on the microstructure are studied and presented. Primary Al3(Zr1-x-y ,Tix , Siy) intermetallics were found in the centre of the α-Al grains. This suggests that UST may have forced the nucleation and refinement of primary intermetallics influencing the subsequent solidification process when Al3(Zr1-x-y , Tix , Siy) act as nucleation sites.
2:30 PM Cancelled
Microstructure Control in A356 Al-Si Alloy via Ultrasonic Melt Treatment: Waleed Khalifa1; Mahmoud Abdu1; Maiada Abdelrahman1; Yoshiki Tsunekawa2; 1Cairo University; 2Toyota Technological Institute
Ultrasonic treatment was conducted to study its effect on the size and morphology of the α-Al phase of the A356 Al-Si-Mg alloy. Treatments were carried out in the temperature range from 700 to 614 °C, i.e. from above the liquidus temperature (619 °C) to semisolid temperatures. The treatment times varied from 15 to 180 s. The results showed that ultrasonic treatment could control the alloy microstructure when applied in the liquid or semisolid states, and was most efficient when applied at a few degrees above the liquidus temperature, e.g., 620 °C, where globule size of 57 μm and roundness between 0.62 and 0.70 were obtained. Ultrasonic treatment times in the order of 15-30 s were sufficient to dramatically refine the size and alter the morphology of the α-Al phase. The refining effect observed in samples treated in semisolid state was due to solid fragmentation and dispersion, while in the liquid state, refining occurred most likely as a result of activation of non-equilibrium nucleation events which was confirmed from experimental simulations performed using succinonitrile polymer.