Microstructure and high temperature strength of age hardenable AA2219 aluminium alloy modified by Sc, Mg and Zr additions

Abstract

In the present work, it was envisaged to develop thermally stable Al–Cu alloy by modifying its chemistry. AA2219 alloys with different levels of scandium (Sc), magnesium (Mg) and zirconium (Zr) were prepared by melting with inert gas (argon) tungsten arc welding. Sc was added in three levels (0·2, 0·4, 0·8%), Mg one level (0·45%) and Zr one level (0·2%). Optical, scanning electron microscopy (SEM), X-ray diffractometry (XRD) and transmission electron microscopy (TEM) were carried out to study the microstructural details. Long time aging studies and hot tensile tests were used to study the high temperature strength of the alloys. High temperature tensile test was performed on the specimens at 250, 350 and 400°C. Room temperature tensile test was carried out for comparative purpose. Electron probe microscopy analysis (EPMA) was carried out to find out the copper segregation in the alloys. Microstructural studies showed that raising Sc content from 0·2 to 0·8% resulted in significant grain refinement. Grain refinement was much more effective with the addition of 0·2%Zr to AA2219 alloy containing 0·8%Sc and 0·45%Mg. Addition of Sc, Mg and Zr was found to increase in eutectic temperature and decrease in freezing range. Hot tensile results were found to be in agreement with results of hardness data. Among all the compositions, AA2219+0·8%Sc+0·45%Mg+0·2%Zr alloy was found to be the best in terms of its high temperature strength.

Enhanced mechanical properties of Al–Si–Cu–Mn–Fe alloys at elevated temperatures through grain refinement and dispersoid strengthening

“…The increase in micron-sized T (Al 20 Cu 2 Mn 3 ) and nano-sized α-Fe precipitates can be mainly attributed to grain refinement [32]. It has been reported that the grain size can influence the amount and size of precipitates in Al–Cu alloys [59,60], which is due to that the refined grains lead to a shorter diffusion distance of Cu, Mn, Fe, and Si atoms during solution treatment [19]. Therefore, during solution treatment, Cu, Mn, Fe, and Si atoms are more homogeneously distributed, resulting in the simultaneous nucleation of a larger number of precipitates.…”

“…On the other hand, iron is one of the primary alloying elements in heat-resistant aluminium alloys. For instance, iron is added to increase the strength of Al-Cu-Mg-Fe-Ni alloys, such as AA2219 and AA2618, at elevated temperatures [18,19]. Therefore, despite the need for iron impurity control, it is a very economical way to develop high-performance heat-resistant aluminium alloys using recycled aluminium.…”

New-Age Al-Cu-Mn-Zr (ACMZ) Alloy for High Temperature-High Strength Applications: A Review

“…The addition of 1.6-2.0 wt % Li also shows excellent mechanical properties for AA2099 (Al-Cu-Li) alloys at high temperature, primarily due to the enhanced thermal stability of T 1 (Al 2 CuLi) precipitates compared to other possible strengthening precipitates like θ 0 and S (Al 2 CuMg) [41]. At higher temperature, T 1 precipitates coarsen instead of dissolving unlike θ 0 or S. In addition, AA2219 alloy possesses improved high temperature performance when micro-alloyed with 0.8 wt% Sc, 0.45 wt% Mg and 0.2 wt% Zr from grain refinement and simultaneous precipitation of Al 3 Sc, Al 3 Zr and Ω precipitates along with other common strengthening precipitates like θ 0 and θ″ [42].…”