Magnesium Technology 2017: Mechanical Behavior: Twinning, Plasticity, Texture, and Fatigue II
Sponsored by: TMS Light Metals Division, TMS: Magnesium Committee
Program Organizers: Kiran Solanki, Arizona State University; Dmytro Orlov, Lund University; Alok Singh, National Institute for Materials Science; Neale Neelameggham, Ind LLC
Wednesday 2:00 PM
March 1, 2017
Location: San Diego Convention Ctr
Session Chair: JB Jordon, The University of Alabama; Alec Davis, University of Manchester
Dynamic Behavior of an AZ31 Alloy under Varying Strain Rates and Stress Triaxialities: Chaitanya Kale1; Mansa Rajagopalan1; Scott Turnage1; Billy Hornbuckle2; Kris Darling2; Suveen Mathaudhu3; Kiran Solanki2; 1Arizona State University; 2Army Research Laboratory; 3University of California, Riverside
Determination of microstructural and mechanical response to real-world loading conditions is imperative for the development of accurate models to predict the failure behavior of structural materials. The dynamic behavior of magnesium alloys is of particular interest to the structural industries as lightweight materials must be able to withstand high impact loading. This study examines the influence of dynamic strain rate on the deformation behavior of a polycrystalline, hot-rolled AZ31 Mg alloy under varying stress triaxialities. The high strain rate testing results indicate that an increase in triaxiality leads to a transition in the deformation mechanisms. Subsequent characterization of microstructure and fracture surfaces were correlated to the mechanical response observed. Finally, these findings provide critical insights into the role of stress-state on dynamic behavior of an AZ31 alloy.
Enhancing the Tensile Response of Magnesium through Simultaneous Addition of Aluminium and Alumina Nanoparticulates: Eugene Wong1; Manoj Gupta2; 1Newcastle University International Singapore; 2National University of Singapore
Lightweight metals, alloys and composites are extremely attractive for weight critical applications in automotive; aerospace; electronics and transportation sectors. The addition of hybrid reinforcements may help to improve both strength and ductility of composites. In the present study, an attempt was made to simultaneously reinforce magnesium with aluminium and varying volume % of alumina nanoparticulates using liquid based casting technique followed by hot extrusion. Microstructural characterization studies revealed minimal porosity, good distribution of intermetallic second phase and good retention and distribution of alumina nanoparticulates. Overall, the tensile properties of the Mg-Al/Al2O3 nanocomposite exhibited enhanced 0.2% yield strength (~40%), ultimate tensile strength (~50%) and ductility (~52%) when compared to magnesium reinforced with similar volume % of Al2O3.
2:40 PM Cancelled
Effect of Solutes Additions on the Microstructure and Mechanical Properties of Cast Mg-Al Based Alloys: Yahia Ali1; Ming-Xing Zhang1; 1University of Queensland
Aluminium is an essential alloying element in most commercially used Mg alloys and particularly AZ series. That is due to its outstanding ability to increasing castability, formability and mechanical properties of Mg. However, seeking higher mechanical properties alloys has always been a hot topic in this research area. Grain refinement, solid solution strengthening and precipitation hardening are all mechanisms to increasing the as-cast mechanical properties of the alloys. In the current work, the effects of 6 different solutes addition, namely titanium, silicon, manganese, copper, calcium and tin, on the microstructure and mechanical properties of Mg-Al based alloys have been studied. In terms of microstructure, results showed that even though higher Q-values can be obtained through increasing the solutes addition, grain refinement is not always associated with the Q-values. In addition, intermetallic compounds played a major role in enhancing the hardness of the alloys.
Enhanced Mechanical Properties of Extruded Mg-9mass%Al-1mass%Zn-2mass%Ca Alloy: Xinsheng Huang1; Yasumasa Chino1; Hironori Ueda2; Masashi Inoue2; Futoshi Kido3; Toshiharu Matsumoto3; 1National Institute of Advanced Industrial Science and Technology; 2Fuji Light Metal Co. Ltd.; 3Tobata Seisakusho Co., Ltd.
In order to investigate the relationships between microstructure and mechanical properties of extruded Mg-9mass%Al-1mass%Zn-2mass%Ca (AZX912) alloy, the AZX912 alloy ingots with and without solution treatment were extruded at different temperatures in a range of 523-673 K. With decreasing extrusion temperature, the grain size of dynamically recrystallized grains decreased, and the amount of fine Mg17Al12 precipitates increased due to dynamic precipitation. All extruded AZX912 alloys exhibited basal texture with basal planes roughly parallel to the extrusion direction and the large spread of (0002) orientation in the radial direction of extruded bar. The basal texture intensities remarkably increased with increasing extrusion temperature. Nanoscale Mg17Al12 precipitates enhance mechanical strength significantly but deteriorate ductility. The bar extruded at 523 K exhibited the highest mechanical strength due to the combined effect of the remarkably refined grain structure and the large amount of nanoscale Mg17Al12 precipitates.
3:20 PM Break
Influence of Strain Path Change on the Microstructure and Mechanical Properties of Duplex Mg-Li Alloy: Yun Zou1; Yang Li2; Hao Guo1; Songsong Xu1; Yu Zhao1; Milin Zhang1; Zhongwu Zhang1; 1Harbin Engineering University; 2Zhengzhou University
The microstructures, texture evolution, and mechanical properties of unidirectionally-rolled and cross-rolled Mg-9Li-6Er alloy were investigated in this paper. The results show that the Mg-9Li-6Er alloy mainly consists of α phase and β phase along with Er5Mg24 eutectic. The strain path was changed between rolling passes during the cross-rolling process, which led to a weaker texture development compared to the conventional unidirectional-rolling method. At the same time, cross-rolling process makes the alloys have a much significant deformation strengthening effect than that of the unidirectionally-rolling process, which can be mainly attributed to the change in strain path, making the α phase distributes disorderly in the β phase and interacts with each other into a network. On the other hand, due to the disordered distribution of matrix phases, uniform plastic deformation is blocked, and thus the ductility is greatly lowered.
Mechanical Properties and Deformation Mechanism of Mg-Y Alloy with Various Grain Sizes: Ichiro Kawarada1; Ruixiao Zheng1; Akinobu Shibata1; Hidetoshi Somekawa2; Shigenobu Ogata3; Nobuhiro Tsuji1; 1Kyoto University; 2National Institute for Material Science; 3Osaka University
In the present study, Mg-Y alloy was provided for high pressure torsion (HPT) and subsequent annealing treatment. After the HPT by 5 rotations, nanocrystalline (NC) structures with an average grain size of about 240 nm having deformed characteristics were obtained. After subsequent annealing at various temperatures for 2-60 min, fully recrystallized structures with different average grain sizes ranging from 0.66 μm to 8.13 μm were obtained. Good balance of tensile strength and ductility could be realized in the fine grained alloys. For the specimen having a mean grain size of 2.13 μm, the yield strength and total tensile elongation were 180 MPa and 37 %, respectively, which were much higher than those of pure Mg with similar grain sizes. The significant contribution of Y on the microstructure and mechanical properties is discussed.
Microstructure and Mechanical Properties of High Pressure Die Cast Mg-Al-Sn-Si Alloys: Andrew Klarner1; Weihua Sun1; Jiashi Miao1; Alan Luo1; 1The Ohio State University
The effect of a small addition of Si was studied to increase the mechanical properties of Mg-Al-Sn alloys. Test specimens were produced by a vacuum die casting process which makes it possible to perform various heat treatments on the alloy. The addition of Si leads to the formation of a binary Mg2Si phase which contributes to an increase in strength in the as-cast condition. Aging treatments were performed to further increase the strength of the alloys by precipitation of fine Mg2Sn, Mg2Si, and Mg17Al12 phases. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) techniques were used to observe these fine precipitates at different stages of the heat treatment and mechanical testing was performed to compare strength and ductility to previous magnesium alloys.
Microstructure and Mechanical Properties of an Extruded Mg-1.58Zn-0.52Gd Alloy: M.G. Jiang1; J.C. Chen2; H. Yan1; C. Xu3; T. Nakata3; S. Kamado3; 1Institute of Metal Research, Chinese Academy of Sciences; 2Xi’an Jiaotong University; 3Nagaoka University of Technology
Mg-1.58Zn-0.52Gd (wt.%) alloy was indirectly extruded at different temperatures and the resulting microstructure, texture and mechanical properties were investigated. The alloy extruded at 350 ℃ exhibited a typical bimodal microstructure, consisting of fine dynamically recrystallized (DRXed) grains of 3.1 μm and coarse unDRXed grains, with high density of fine spherical Mg3Zn3Gd2 phase, and a strong [10-10] fiber texture, thereby resulting in high yield strength of 283 MPa and low elongation of 10.0%. With increasing extrusion temperature, the yield strength gradually decreased with an increase in DRXed grain size according to the Hall-Petch relation, while the elongation increased due to the decreased unDRX fraction, suppressing crack initiation at twins in coarse unDRXed grains, and weakened basal texture. As a result, the alloy extruded at 400 ℃ showed yield strength of 161 MPa and elongation of 24.7%.
Modelling Magnesium Alloys for Improved Isotropic and Symmetric Yield Behaviour: Alec Davis1; Joseph Robson1; 1University of Manchester
One of the main limitations of current wrought magnesium alloys is their high level of mechanical anisotropy and asymmetry. It has been proposed that careful choice of precipitates in age-hardenable wrought magnesium alloys may reduce anisotropy by selectively strengthening weaker deformation systems, reducing the inherent single crystal plastic anisotropy associated with the magnesium hexagonal close packed structure. In the present work, a model has been used to explore the ideal precipitate distribution, habit, and morphology to produce the most isotropic yield behaviour. The predictions of this model have been compared with the known precipitate characteristics in several promising magnesium alloy systems. It has been predicted that by selection of the correct alloy system, a desirable combination of high strength and greatly reduced anisotropy is attainable. This model based design approach is novel for magnesium alloys, and is currently being validated by manufacturing the optimised alloys.