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Abstract

Photo 1 A dendritical structure in Al-3.4% Zr alloy solidified in iron mold. (TEM)Photo 3 Small angular structure with a characteristic fringe in Al-2.4%Zr alloy solidified by the hammer quenching method. (TEM) Vol. 31, No. 12 795

Nucleation and Precipitation Strengthening in Dilute Al-Ti and Al-Zr Alloys

“…pct Ti alloys aged between 400°C and 550°C. They also noted that the decomposition kinetics of Al 3 Ti were sluggish compared with those of Al alloyed with other elements of the same subgroup, Zr or [19] (b) Kerr et al, [36] (c) Hori et al, [75,76] and (d) Hori et al [24] Hf. Pandey and Suryanarayana [78] also compared the decomposition behavior of rapidly solidified Al alloyed with Ti, Zr, or Hf (Group 4 elements) and noted that a metastable Al 3 M (L1 2 ) ordered phase is observed in Al-Zr and Al-Hf alloys but not in Al-Ti alloys.…”

“…As demonstrated in Figure 1, the marked grain refinement observed with increasing Ti concentration is due to primary precipitation of Al 3 Ti in the melt, and increasing the Ti concentration does not increase the amount of Ti retained in a-Al solid solution. The inter-relationships among solidification rates, solute concentrations, and solidified microstructures of the Al-Ti and Al-Zr binary systems have been the subject of prior studies, [19,24,36,75,76] which are summarized in Figure 8. These curves show the measured solidification rate, as a function of solute concentration, necessary to suppress primary precipitation of Al 3 Ti or Al 3 Zr, thereby obtaining supersaturated a-Al solid solution.…”

“…[19] These metastable particles are isostructural to, and exhibit a small lattice parameter mismatch with, the a-Al solid solution, and therefore act as efficient heterogeneous nucleants during solidification of a-Al. The resulting grain refinement in cast alloys is frequently exploited industrially by Ti additions to Al [19][20][21][22] and has also been observed in Al-Zr [19,23,24] and Al-Hf [25][26][27] alloys when primary precipitation of Al 3 M (L1 2 ) occurs. The refined grain size, however, is undesirable for applications where creep resistance is required.…”

Grain Refinement during Rapid Solidification of Aluminum–Zirconium Alloys Using Electrospark Deposition

“…Hori et al 19,20) have reported the relationship between the cooling rate and the solute content for AlZr alloys, which is shown in Fig. 2, and have identified processing conditions resulting in non-equilibrium solidification structure, i.e., supersaturated solid solution or L1 2 Al 3 Zr within Al.…”

Formation of Nano-Microstructured Aluminum Alloy Film Using Thermal Spray Gun with Ultra Rapid Cooling

“…When melted alloys are rapidly solidi ed to form a ribbon shape at cooling rates of about 10 5 and 10 6 K/s by a single roller technique, the solid solubility increases and a nano structure is formed. For example, the microstructure of aluminum containing titanium solidi ed using a single roller was examined [5][6][7] . Furthermore, new high speci c strength aluminum alloys for use in lighter, more functional automobile components have been developed by optimization of the chemical composition and the rapid solidi cation technique [8][9][10] .…”