Investigation of Thermal Stability of Microstructure and Mechanical Properties of Bimetallic Fine-Grained Wires from Al–0.25%Zr–(Sc,Hf) Alloys

Abstract

Thermal stability of composite bimetallic wires from five novel microalloyed aluminum alloys with different contents of alloying elements (Zr, Sc, and Hf) is investigated. The alloy workpieces were obtained by induction-casting in a vacuum, preliminary severe plastic deformation, and annealing providing the formation of a uniform microstructure and the nucleation of stabilizing intermetallide Al3(Zr,Sc,Hf) nanoparticles. The wires of 0.26 mm in diameter were obtained by simultaneous deformation of the Al alloy with Cu shell. The bimetallic wires demonstrated high strength and improved thermal stability. After annealing at 450–500 °C, a uniform fine-grained microstructure formed in the wire (the mean grain sizes in the annealed Al wires are 3–5 μm). An increased hardness and strength due to nucleation of the Al3(Sc,Hf) particles was observed. A diffusion of Cu from the shell into the surface layers of the Al wire was observed when heating up to 400–450 °C. The Cu diffusion depth into the annealed Al wire surfaces reached 30–40 μm. The maximum elongation to failure of the wires (20–30%) was achieved after annealing at 350 °C. The maximum values of microhardness (Hv = 500–520 MPa) and of ultimate strength (σb = 195–235 MPa) after annealing at 500 °C were observed for the wires made from the Al alloys alloyed with 0.05–0.1% Sc.

Effect of Sc:Zr Ratio on Superplastic Behavior of Ultrafine-grained Al-6%Mg-Sc-Zr Alloys

“…Nowadays much effort is taken to find ways to replace scandium with cheaper rare earth elements (REE) and transition metals (TM) [23][24][32][33][34]38,43,53]. The effect of Zr [23][24][25]29,30,[32][33][34][35]39,51,52,53,69,70],…”

“…Er [53,54,56,[59][60][61]63,66,71,76], Hf [25,53,54,57,63,70,76], Yb [53,55,62,65,66,73], and Y [54,58,64,66,67,72,74,75] is studied thoroughly, including the combined effect of several doping elements on the kinetics of precipitation and growth of particles with L12 structure in aluminum alloys. Some works are worth mentioning as they demonstrate that precipitation of L12 particles in new alloys can develop in line with the discontinuous precipitation mechanism [51,61,[77][78][79][80][81][82][83].…”

“…Some works are worth mentioning as they demonstrate that precipitation of L12 particles in new alloys can develop in line with the discontinuous precipitation mechanism [51,61,[77][78][79][80][81][82][83]. The microstructure and mechanical properties of fine-grained aluminum alloys, simultaneously doped with several REEs and TMs, were studied in detail in [21][22][23][24][25][26][27][28][29][30][31][32]34,43,52,54,[56][57][58]60,61,63,[65][66][67][68][69][70][72][73][74]76].…”

Effect of Sc, Hf, and Yb Additions on Superplasticity of a Fine-grained Al-0.4%Zr Alloy

“…The wires are made by deformation (rolling, drawing, etc. ), and precipitation of Al3(Zr,X) nanoparticles at low temperatures ensures better thermal stability of an ultrafine-grained (UFG) microstructure of a deformed aluminum alloy [68,69].…”

“…This study focuses on Al-Zr-Sc, Al-Zr-Hf, Al-Zr-Yb alloys as well as alloys simultaneously alloyed with several doping elements. Precipitation of Al3(Zr,Sc) and Al3(Zr,Hf) secondary particles in Al-Zr-(Sc,Hf) alloys is still more intensive at lower temperatures compared to Al3Zr in Al-Zr alloys [15,40,43,45,69]. Therefore, during low-temperature heating, it is possible to ensure precipitation of a larger volume fraction of Al3(Zr,X) secondary particles compared to that of Al3Zr particles.…”