Multiscale & in-situ forming analysis of AZ31 magnesium alloy under different strain paths

Alkan, Kıvanç
Formability of AZ31 Magnesium alloy is limited and strain path dependent below 180 ᵒC. In this thesis, formability behavior and fracture mechanisms of AZ31 Magnesium alloy are investigated by in-plane biaxial testing. In-situ and multiscale strain analysis reveal the microstructural features and deformation mechanisms responsible form the unusual forming behavior of the AZ31 alloy and offer possible solutions to control the forming defects and instabilities. The strain measurements show that the equivalent fracture strains of both uniaxial and equibiaxial stress states are nearly the same, however heterogeneous deformation is observed at both loading conditions. At microscale, localization ratio (Ԑlocalized/Ԑmean) is 3 in uniaxial tension and 20 in equibiaxial stretching. The localizations at the microscale reveal themselves at the macroscale and limit the formability, especially under equibiaxial stretching, by early plastic instabilities. Twinning and grain boundary slip are the main deformation mechanisms responsible for the localizations at both conditions. A detailed analysis of the microstructure by EBSD indicates that the slip activity decreases from uniaxial tension to equibiaxial stretching, while the formation of {101 ̅2}〈101 ̅1〉 tension twins dominates the deformation. In uniaxial tension, intergranular fracture occurs due to the slip assisted grain boundary sliding but in equibiaxial stretching, a mixture of a transgranular and intergranular fracture leads to the ultimate failure of the samples. Therefore, twinning activity and grain boundary slip should be suppressed to increase the formability. A uniform distribution of slip within the grains should yield the optimum formability for AZ31 Magnesium alloy.


Controlling and modelling of twin induced strain localization in rolling of magnesium AZ31
İsmail, Kübra; Efe, Mert; Department of Metallurgical and Materials Engineering (2019)
Formability of AZ31 Magnesium alloy has certain limits below 200 ℃ and depends strongly on temperature, due to the strain localization and shear banding associated with the twinning activity. In this thesis, magnesium sheets with basal, off-basal (90° tilted) and mixed (50% basal + 50% off-basal) textures are rolled between room temperature and 165 ℃ to understand and control the twinning-induced localizations. By increasing strain from 0.1 to 0.6 and raising the temperature, the fraction of flow localized ...
Electrolytic magnesium production using coaxial electrodes
Demirci, Gökhan; Karakaya, İshak; Department of Metallurgical and Materials Engineering (2006)
Main reason for the current losses in electrolytic magnesium production is the reaction between electrode products. Present study was devoted to effective separation of chlorine gas from the electrolysis environment by a new cell design and thus reducing the extent of back reaction between magnesium and chlorine to decrease energy consumption values. The new cell design was tested by changing temperature, cathode surface, current density, anode cathode distance and electrolyte composition. Both the voltages...
Ageing characteristics of copper based shape memory alloys
Tarhan, Elif; Bor, Şakir; Department of Metallurgical and Materials Engineering (2004)
Martensite-to-Beta transformation temperatures of CuAlNiMn and CuAlNi shape memory alloys has been determined by differential scanning calorimetry (DSC). In CuAlNiMn alloys, each new betatizing treatment has resulted in randomly varying transformation temperatures on the same specimen and an anomalously diffuse and serrated Martensite-to-Beta transformation peaks in the first cycle. Therefore, as quenched alloy samples were thermally cycled for three times in DSC prior to ageing to obtain thermally stable a...
Molecular dynamics study of random and ordered metals and metal alloys
Kart, Hasan Hüseyin; Tomak, Mehmet; Department of Physics (2004)
The solid, liquid, and solidification properties of Pd, Ag pure metals and especially PdxAg1-x alloys are studied by using the molecular dynamics simulation. The effects of temperature and concentration on the physical properties of PdxÞAg1-x are analyzed. Sutton-Chen (SC) and Quantum Sutton-Chen (Q-SC) many-body potentials are used as interatomic interactions which enable one to investigate the thermodynamic, static, and dynamical properties of transition metals. The simulation results such as cohesive ene...
Nanocrystallization in Cu-Zr-Al-Sm Bulk Metallic Glasses
Sıkan, Fatih; Yaşar, Bengisu; KALAY, İLKAY (Springer Science and Business Media LLC, 2018-04-01)
The effect of rare-earth element (Sm) microalloying on the thermal stability and crystallization kinetics of melt-spun ribbons and suction-cast rods of Zr48Cu38.4Al9.6Sm4 alloy were investigated using differential scanning calorimetry (DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM), and atom probe tomography (APT). The XRD results of constant heating rate annealing indicated that amorphous Zr48Cu38.4Al9.6Sm4 melt-spun ribbons devitrifies into Cu2Sm at 673 K (400 A degrees C). The sequ...
Citation Formats
K. Alkan, “Multiscale & in-situ forming analysis of AZ31 magnesium alloy under different strain paths,” M.S. - Master of Science, Middle East Technical University, 2018.