Abstract
The effects of Ti addition on the microstructural evolution and mechanical properties of Al–7.6Zn–2.6Mg–2.0Cu–0.1Zr alloy were investigated at each process step such as casting, extrusion, solution treatment, and aging. The addition of titanium causes refinement of both the grains and bulky η-Mg(Zn,Cu,Al)2 particles in the as-cast alloys. After hot extrusion, the Ti-added alloy has increased amounts of recrystallized grains by particle-stimulated nucleation, decreasing the strength of the as-extruded alloy. Titanium addition causes size decrease of L12 precipitates and increases the number density of them while substituting Zr site with Ti, that is, Al3(Zr,Ti). Besides, the Al18Mg3Ti2 phase is formed by Ti addition during solution treatment, which acts as a heterogeneous nucleation of η precipitate. The strength of the aged alloys is improved by the formation of fine L12 precipitates, grain refinement, and the refinement of bulky η-phases.KeywordsMicrostructureAluminum alloyTitanium additionExtrusionPrecipitate
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