Aluminum Alloys, Processing and Characterization: Heat Treatment
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee
Program Organizers: Yanjun Li, Norwegian University of Science and Technology
Tuesday 8:30 AM
February 28, 2017
Location: San Diego Convention Ctr
Session Chair: Ramasis Goswami, Naval Research Laboratory
8:30 AM Introductory Comments
The Optimization of the Homogenization Treatment of AA7075: Gheorghe Dobra1; Ioan Sava1; Marin Petre1; Gheorghe Popa1; 1ALRO
The homogenization treatment of 7075 aluminium alloy slabs is required for ensuring the technological properties for later processing. This usually has two stages. The soaking time in the second stage has an important influence. In order to evaluate the influence of this parameter, the homogenization, solution heat treatment, quenching and ageing treatment were simulated in the laboratory at various homogenization soaking time between 4 and 24 hours. The evolution of the eutectic structures in the as-cast and homogenized 7075 aluminium alloy were investigated by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), differential scanning calorimetry (DSC) and tensile test.The results demonstrate that from many standpoints (mechanical properties, microstructure etc.) the complete dissolution of all soluble phases ends before the limit of 20 hours that is considered as standard all over industry.
Precipitation Modeling and Validation of Al-5%Cu-0.4%Mn Alloy Using Quench Factor Analysis: Yisen Hu1; Gang Wang1; Wenguang Wang1; Mao Ye1; Yiming Rong1; 1Tsinghua University
Quench factor analysis has been widely used to describe how precipitation in quenching affects the development of properties of aluminum alloys in subsequent aging treatment. To minimize the amount of effort and time, Jominy end quench was used to conduct quench factor analysis. The author applied Jominy end quench test to Al-5%Cu-0.4%Mn alloy, followed by different artificial aging time, and Rockwell hardness was measured along the length of the samples. Quench factor analysis was conducted with measured data. Critical time at different temperatures of Al-5%Cu-0.4%Mn was calculated with the kinetic parameters and 400 degree Celsius was demonstrated to be the sensitive temperature. In addition, the effect of quenching rate on aging was studied and the strengthening effects of precipitation during quenching and aging were compared. The results revealed that with decreasing quenching rate, the peak aging time and the hardness of as-quenched increased, whereas the peak hardness decreased.
Young’s Modulus of Al-Si-Mg-Cu Based Alloys under Different Heat Treatment Processes: Sajjad Amirkhanlou1; Shouxun Ji1; Yijie Zhang1; Douglas Watson2; Zhongyun Fan1; 1Brunel University London; 2Jaguar Cars Ltd
The Young’s modulus of an Al-Si-Mg-Cu alloy reinforced with TiB2 and Mg2Si was investigated under different heat treatment processes, including T4, T6, T7 and O temper. The microstructural evaluation and mechanical properties of the developed Al-Si-Mg-Cu alloy was examined by X-ray diffractometer (XRD), optical microscopy (OM), scanning and high resolution transmission electron microscopies (SEM and HRTEM), ultrasonic pulse technique and tensile test. The results revealed that the alloys, in all heat treatment conditions, consist of Si, Mg2Si and TiB2 phases, which are responsible for the increase of Young’s modulus. HRTEM micrographs showed the formation of incoherent, clean and smooth interfaces between aluminium matrix and TiB2 particles. The alloys with 93 GPa Young’s modulus are still castable for making shaped castings. In comparison with the conventional aluminium alloys that have Young’s modulus at a level of 70 GPa, 30% increase of Young’s modulus can be achieved by the developed alloys.
Intergranular Corrosion Investigation on EN-AW 6082 Redraw Rod: Luisa Marzoli1; Dominque Cance2; Christiane Matthies1; Magali Guizard2; Peter Baumgart2; Hubert Koch1; 1TRIMETAluminium SE; 2TRIMET France
The request for aluminium with enhanced properties, such as an improved resistance to intergranular corrosion for the 6xxx alloys has risen in the past years. In the past years there have been investigations on the IGC behaviour of 6xxx extrusion alloys, but no studies about the behaviour of rod are known to the authors of this paper. In this article, the IGC behaviour of 6082 rod will be investigated. The rods were produced by TRIMET in Castelsarrasin with a continuous casting and rolling process. They were subsequently, in the labs of TRIMET, homogenised, drawn with final area reduction of 53%, annealed and heat treated. The samples were than tested according to the VW PV1113 for ICG of 6XXX alloys, a test used on extruded profiles, permitting a comparison of the results. Results indicate that chemical composition and process parameters have a strong influence to the corrosion sensitivity of this material.
10:15 AM Break
The Influence of Process Parameters and Thermomechanical History on Streaking Defects in AA6060 Extrusions: Steven Babaniaris1; Aiden Beer1; Matthew Barnett1; 1Deakin University - Institute for Frontier Materials
Streaking is a common surface defect on architectural extrusions. The current study investigates the effect of processing parameters and thermomechanical history on the surface finish of a streaked AA6060 extrusion. Streaked profiles were intentionally produced via extrusion using a die with internal geometry deliberately designed to produce thermomechanical variation in specific regions of the profile geometry. Extrusions were conducted at various ram speeds and the profiles were given an anodization pre-treatment process to reveal streaking in the designated regions. Thermomechanical variation was analysed using the “ALE” code HyperXtrude®. The surface profile and roughness of the treated and mill finish extrudates were analysed using optical profilometry. The presence of the streaks were associated with strain rate variability as determined by the die geometry, independent of the ram speed. Although there were no significant differences in roughness, the streaked regions of the profile were more recessed compared to the bulk regions.
Effect of Heat-treatment on Microstructure and Mechanical Properties of Sonicated Multicomponent AlMgSiCuZn Alloy: Kwangjun Euh1; Jae-Gil Jung1; Eunji Baek1; Jung-Moo Lee1; Hyoung-Wook Kim1; 1Korea Institute of Materials Science
In this study, an Al63Mg8Si9Cu10Zn10 (in wt%) alloy is fabricated with a high volume fraction of coarse secondary phases, which is higher fraction than in the conventional piston alloys. Ingots are cast in a permanent mold after an ultrasonic melt treatment for 60s at the temperature range of 750 to 700oC. Microstructure of AlMgSiCuZn alloy consists of Si, Zn, Mg2Si, Q-Al5Cu2Mg8Si6, and θ-Al2Cu phases. By the annealing at 440oC, Q-phase at the vicinity of blocky Mg2Si phase grows and the roundness of the second phases increases with respect to the annealing time. Compared with the as-cast specimen, compressive fracture stress of the annealed specimens at room temperature increases. However, maximum compressive stress at 350oC is slightly decreased by annealing. The effect of annealing on the mechanical properties of AlMgSiCuZn alloy is elucidated by means of microstructural analysis.
Effect of Interrupted Quenching on Al-Zn-Mg-Cu Alloys: Gernot K.-H. Kolb1; Helmut Antrekowitsch1; Daniel Pöschmann2; Peter Uggowitzer3; Stefan Pogatscher1; 1Montanuniversitaet Leoben; 2AMAG rolling GmbH; 3ETH Zürich
Al-Zn-Mg-Cu alloys are widely used in aged-hardened condition for aircraft applications because of their high strength, adequate fracture toughness, stress corrosion cracking resistance and good machinability. In this study the effect of interrupted quenching (I.Q.) from solution temperature to 25–225°C on subsequent artificial aging was studied. Hardness measurements, tensile tests and instrumented impact tests were used to characterize the mechanical properties of Al-Zn-Mg-Cu plates. Transmission electron microscopy was conducted to investigate the microstructure. The results show that a high hardness can be reached directly after I.Q. for a medium I.Q. temperature. Compared to standard water quenching,the results showed that hardening kinetics and the age hardening response during artificial aging can be enhanced for I.Q. at medium artificial aging temperatures, but are reduced at high temperatures. I.Q. at high temperatures affects subsequent artificial aging via the formation of precipitates, which contribute less to hardening but consume a significant amount of solute.
11:45 AM Cancelled
Manganese-induced Precipitation in a Modified AA6061 (Al-Mg-Si-Cu) Alloy during Homogenization: Gongwang Zhang1; Yi Han2; Qi Zhou3; Hiromi Nagaumi2; Gang Sha3; Chad Parish4; Donovan Leonard4; Tongguang Zhai1; 1University of Kentucky; 2Suzhou Research Institute for Nonferrous Metals; 3Nanjing University of Science and Technology; 4Oak Ridge National Laboratory
A modified AA6061 Al alloy with addition of Mn, Cr and Cu was homogenized at temperatures ranging from 350 °C to 550 °C after casting. STEM and atom probe tomography (APT) were employed to investigate the formation mechanism for α-dispersoids during homogenization. It was found that the lathe-shaped Q-AlMgSiCu phase was transferred into strings of Mn-rich precipitates in the regions where Mn tended to segregate to the interface between the Q-phase and the matrix in the early stage of homogenization, in contrast, the lathe-shaped Q-AlMgSiCu phase remained unchanged in the region where Mn segregation could hardly occur at the Q and matrix interface. This could indicate that Mn might induce the phase transformation from Q to α-dispersoids in the early stage of homogenization. The Q-phase was the precursor phase for the formation of α-dispersoids. The segregation and partitioning of Mn to Q-phase might be energetically favorable to induce α-dispersoids precipitation.