Microstructural Modulations Enhance the Mechanical Properties in Al–Cu–(Si, Ga) Ultrafine Composites

Abstract

Adding small amounts of Si or Ga (3 at.%) to the eutectic Al83Cu17 alloy yields an ultrafine bimodal eutectic composite microstructure upon solidification. The as‐solidified alloys exhibit a distinct microstructural length‐scale hierarchy leading to a high fracture strength of around 1 GPa combined with a large compressive plastic strain of up to 30% at room temperature. The present results suggest that the mechanical properties of the ultrafine bimodal eutectic composites are strongly related to their microstructural characteristics, namely phase evolution, length‐scales, and distribution of the constituent phases.

Micro-to-nano-scale deformation mechanisms of a bimodal ultrafine eutectic composite

“…The quantitative chemical analysis of the primary coarse eutectic colony and fine eutectic matrix shows that there are 96.80 ± 0.5 at.% Al, 2.65 ± 0.05 at.% Cu and 0.55 ± 0.02 at.% Si in the α-Al phase, 63.78 ± 0.3 at.% Al, 35.37 ± 0.2 at.% Cu and 0.85 ± 0.05 at.% Si in the θ-Al 2 Cu phase (for coarse eutectic) and 96.33 ± 0.5 at.% Al, 2.71 ± 0.05 at.% Cu and 0.96 ± 0.02 at.% Si in the α-Al phase, 61.34 ± 0.3 at.% Al, 36.75 ± 0.2 at.% Cu and 1.91 ± 0.05 at.% Si in the θ-Al 2 Cu phase and 10.33 ± 0.1 at.% Al, 6.53 ± 0.05 at.% Cu and 83.14 ± 0.5 at.% Si in the Si phase (for fine eutectic matrix), respectively. This reveals that partitioning of Si has a significant influence to primarily form the coarse eutectic structure with a typical lamellar structure, stabilized by the topological and crystallographic anisotropy of the α-Al and θ-Al 2 Cu phases upon solidification1617. Figure 1d displays a typical room temperature engineering stress-strain curve of the as-cast Al 81 Cu 13 Si 6 BUEC under tensile testing.…”

“…1b. From previous investigations on the microscopic deformation mechanism of UEAs and BUECs817, it is known that the dimples on the fracture surface are a result of the rotation of the eutectic colonies with length-scale heterogeneity along the boundaries of the spherical eutectic colonies. Such rotational motion of the eutectic colonies often accompanies complex plastic flow features such as wavy flow patterns to effectively dissipate the localization of the shear stress during deformation18.…”

Solid-state phase transformation-induced heterogeneous duplex structure in Ti–Sn–Fe alloys

“…2[(c) and (d)] obtained from the dark and bright contrast areas denoted as 'c' and 'd' in Fig. 2(a) correspond to the and [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] zone axes of the hexagonal Ti 3 Sn and ␣-Ti phases, respectively. Moreover, it is worth to note that the splitting diffraction intensity from the Ti 3 Sn phase as shown in Fig.…”

“…For example, a decrease in the lamellar spacing of the eutectic matrix in Ti-based ultra-fine eutectic composites results in the enhancement of the strength [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. In this scenario, systematic microstructural investigation reveals the Fe addition into the binary Ti-Sn alloy can have a strong influence to reduce the lamellar spacing and further refine twinning in Ti 3 Sn phase, which is a key to increasing the strength of the Ti-Sn-Fe alloys.…”

Hybrid nanostructured aluminum alloy with super-high strength

“…However, the yield strength level of these Al alloys is, in general, limited to~700 MPa. 5 Recently, the development of high-strength Al alloys has been carried out through two main approaches: [5][6][7][8][9][10][11] (1) the creation of ultra-fine-grained or nanocrystalline (NC) Al alloys that, owing to their refined microstructure, display very high strength along with appreciable plasticity, and (2) the production of Al-based metallic glasses (MGs) that are free of crystalline defects such as GBs or dislocations and thus have very high strength. Although these approaches are quite effective for the production of high-strength Al alloys, critical limitations still exist.…”