Microstructure and Mechanical Properties of Novel Quasibinary Al-Cu-Yb and Al-Cu-Gd Alloys

Abstract

Microstructure of Al–Cu–Yb and Al-Cu-Gd alloys at casting, hot-rolled -cold-rolled and annealed state were observed; the effect of annealing on the microstructure was studied, as were the mechanical properties and forming properties of the alloys, and the mechanism of action was explored. Analysis of the solidification process showed that the primary Al solidification is followed by the eutectic reaction. The second Al8Cu4Yb and Al8Cu4Gd phases play an important role as recrystallization inhibitor. The Al3Yb or (Al, Cu)17Yb2 phase inclusions are present in the Al-Cu-Yb alloy at the boundary between the eutectic and aluminum dendrites. The recrystallization starting temperature of the alloys is in the range of 250–350 °C after rolling with previous quenching at 590 and 605 °C for Al-Cu-Yb and Al-Cu-Gd, respectively. The hardness and tensile properties of Al-Cu-Yb and Al-Cu-Gd as-rolled alloys are reduced by increasing the annealing temperature and time. The as-rolled alloys have high mechanical properties: YS = 303 MPa, UTS = 327 MPa and El. = 3.2% for Al-Cu-Yb alloy, while YS = 290 MPa, UTS = 315 MPa and El. = 2.1% for Al-Cu-Gd alloy.

Effect of Zr on Microstructure and Mechanical Properties of the Al–Cu–Yb and Al–Cu–Gd Alloys

“…Both alloys' sheets were processed in the same regimes, therefore we suggest a similar role for the dislocation and substructure strengthening mechanisms in the studied alloys. The similar structure was formed in the Zr-free alloys [14], with the same content of Cu, Yb, and Gd. The eutectic originated particles and copper dissolved in the Al solid solution provided an equivalent contribution to the YS of the Zr-free alloys.…”

“…The XRD patterns of the as-cast AlCuYbZr and AlCuGdZr alloys in comparison with the Zr-free alloys are shown in Figure 3 [14]. The X-ray diffraction analysis of Al-CuYbZr alloy in Figure 3a reveals peaks for aluminum, Al8Cu4Yb, and small peaks of the Al3Yb or (Al,Cu)17Yb2 phases.…”

“…The AlCuYbZr and AlCuGdZr alloys possessed a good ductility of 10.5% and 8%, respectively, at an annealing temperature of 300 • C for 10 min with YS of 207 MPa for both alloys. The AlCuYbZr and AlCuGdZr alloys had higher mechanical tensile properties than AlCuYb and AlCuGd [14] after annealing at temperatures above 150 • C due to the thermal stability of these alloys, which were obtained by adding Zr. Figure 9 shows the grain structure of the AlCuYbZr and AlCuGdZr alloys annealed at 350-550 °C after rolling.…”

“…The quasi-binary alloys of the Al-Cu-REM system have been investigated by several researchers, for example Al-Cu-Ce [7,8], Al-Cu-Y [9][10][11], and Al-Cu-Er [9,12,13], with an atomic ratio of 4/1 (Cu/REM) due to the formation of an Al 8 Cu 4 REM phase of a crystallization origin, which increases the mechanical properties of the Al-Cu alloys. This alloying principle was used in the investigation of the ternary quasi-binary Al-4.4Cu-2.5Yb and Al-4.5Cu-2.5Gd alloys [14]. Recently, some studies have investigated the effect of zirconium on the microstructure and precipitation strengthening of Al-Cu-RE alloys.…”

Optimizing the Heat Treatment Method to Improve the Aging Response of Al-Fe-Ni-Sc-Zr Alloys

“…It is a novel idea to use alloy elements (i.e., rare earth (Re) and transitional metal (TM) elements) with a slower diffusion rate to develop a new series of heat-resistant Al alloys. For example, Re elements (i.e., Y [6], Er [6,7], Yb [8], or Gd [8]) were used to develop novel heat-resistant Al-Cu-based alloys. These things considered, some eutectic systems with good casting properties (i.e., Al-Re (Re = La, Ce, Nd) and Al-TM (TM = Ni, Fe)) were proposed [9][10][11][12][13].…”