Heat Treatment of Aluminum Foundry Alloys （热处理的铝铸造合金）.pdf

Heat Treatment of Aluminum Foundry Alloys Fred Major Rio Tinto Alcan OUTLINE • Basics of Heat Treatment (What is happening to the metal at each step). – Atomic Structure of Aluminum – Deformation Mechanisms – Strengthening Mechanisms – Heat Treatment • Solutionizing • Quenching • Aging • Common Tempers • Impact of alloy element content and aging temperature – Microstructural Effects • DAS (ductility) and defect structure (fatigue) – Typical spreads encountered in commercial castings • USCAR Database examples – Quiz • Alternatives to T6 July 2008 Foundry Alloy Heat Treatment Seminar for WPI/MPI ©Alcan International Ltd., 2008 2 Basic Slip Systems in FCC Metals (Aluminum) Unit Cell July 2008 Foundry Alloy Heat Treatment Seminar for WPI/MPI ©Alcan International Ltd., 2008 3 Basic Slip Systems in FCC Metals (Aluminum) Metals deform through the motion of layers of atoms, usually along the planes where they are most closely packed together. July 2008 Foundry Alloy Heat Treatment Seminar for WPI/MPI ©Alcan International Ltd., 2008 4 Basic Slip Systems in FCC Metals (Aluminum) To perform the operation shown above on a perfect crystal would require enormous Force as every bond would have to be broken and reformed. Metals are not observed to be that strong. Why? July 2008 Foundry Alloy Heat Treatment Seminar for WPI/MPI ©Alcan International Ltd., 2008 5 Dislocation Mechanism for Metal Deformation Dislocations Provide a Mechanism that makes metals soft and ductile (most times, too soft) •Obstacles to dislocations strengthen the metal •May include particles, solute atoms, grain boundaries, other dislocations