Quench Sensitivity in a Dispersoid-Containing Al-Mg-Si Alloy
- PDF / 2,117,277 Bytes
- 13 Pages / 593.972 x 792 pts Page_size
- 80 Downloads / 213 Views
NTRODUCTION
ALUMINUM alloys find broad use in many applications including the construction, aerospace and most recently automotive industries. 6000 series alloys in particular have an excellent combination of strength-toweight ratio, corrosion resistance. and formability particularly through extrusion, rolling, and other thermomechanical processing operations. One of the processing-related issues that can affect the properties of these alloys is known as quench sensitivity. Quench sensitivity describes the effect that cooling rate, after homogenization or solution treatment of an alloy, has on the loss of properties, particularly strength. While 7000 series of Al-based alloys are known to be highly KATHARINA STROBEL is with the AMAG Austria Metall, 5282 Braunau-Ranshofen, Austria. MARK A. EASTON is with the School of Engineering, RMIT University, Carlton, VIC 3053, Australia. Contact e-mail address: [email protected]. MATTHEW D.H. LAY is with FB Rice, 90 Collins Street, Melbourne, VIC 3000, Australia. PAUL A. ROMETSCH and NICK C. PARSON are with Rio Tinto Aluminium, Arvida Research and Development Center, Jonquie`re, QC G7S 4K8, Canada. SUMING ZHU is with the Department of Materials Science and Engineering, Monash University, VIC 3800, Australia and also with the School of Engineering, RMIT University. LISA SWEET is with the Department of Materials Science and Engineering, Monash University. ANITA J. HILL is with CSIRO Manufacturing, Clayton, VIC 3169, Australia. Manuscript submitted August 9, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS A
quench sensitive,[1] Al-Mg-Si-based 6000 series alloys, particularly those containing transition metals, can also show some degree of quench sensitivity.[2,3] The factors influencing quench sensitivity include dispersoid density, vacancy concentration, and the kinetics of precipitation. Dispersoids are introduced into the higher-strength 6000 series alloys to control recrystallization and to improve fracture toughness. Dispersoids normally form during the heating stage of homogenization treatment in alloys containing Si, Fe, and other transition metals, such as Mn and Cr.[4–9] It has been shown that dispersoids play an important role in the quench sensitivity of 6000 series alloys as nonhardening Mg-Si phases tend to precipitate on them during cooling.[3,10,11] Since the formation of dispersoids is relatively complex,[5,12–15] careful temperature control is required in order to obtain a homogeneous distribution.[4,7,12,13] The composition, crystal structure, and number density of dispersoids strongly depend on the alloy composition. In most 6000 series alloys, the dispersoids are typically of Al15Mn3Si2-phase with a simple cubic structure.[16,17] If the Fe content exceeds a certain limit (Mn/Fe < 1.6[16]), a body-centered cubic a-Al12Fe3Si-phase tends to form instead.[16] Both dispersoid phases, however, have the same lattice parameter (a = 12.6 A˚) so that they have the same lattice mismatch with the Al matrix. As the dispersoid/matrix interface is very similar in common 60
Data Loading...
