Aging behavior and microstructure evolution in the processing of aluminum alloys

Precipitation in nanostructured alloys: A brief review

“…Precipitation strengthening has been utilized to achieve superior strength in heat-treatable Al alloys, such as 2xxx, 6xxx, 7xxx series, and some of the 8xxx series, since the early discovery of this mechanism in Al-Cu and Al-Mg alloys a century ago. 14 While aging tempers have been well established for conventional CG Al alloys to tailor the evolved microstructures, the precipitation and age-hardening kinetics in UFG Al alloys did not gain attention until recently. 13,14 Here, we selected Al 7xxx series alloy (Al-Zn-Mg-Cu) as a proxy for precipitation-strengthened Al alloys.…”

“…14 While aging tempers have been well established for conventional CG Al alloys to tailor the evolved microstructures, the precipitation and age-hardening kinetics in UFG Al alloys did not gain attention until recently. 13,14 Here, we selected Al 7xxx series alloy (Al-Zn-Mg-Cu) as a proxy for precipitation-strengthened Al alloys. Upon solution treatment followed by aging, the following reactions occur in a sequence in Al 7xxx alloys: supersaturated solid-solution → coherent Guinier-Preston (GP) zones → metastable semicoherent η′-MgZn 2 → equilibrium incoherent η-MgZn 2 10,15,16…”

Review of Techniques for Improvement of Softening Behavior of Age-Hardening Aluminum Alloy Welded Joints

“…According to the strengthening mechanisms of aluminum alloys, they can be divided into two categories: (I) heat-treatable aluminum alloys and (II) non-heat-treatable aluminum alloys [ 6 ], as shown in Figure 1 . By controlling a sequence of thermal treatment processes involving solution heat treatment and quenching, the aluminum alloys that have the capability of forming a supersaturation solid solution and can be strengthened by the consequent formation of coherent fine precipitates with aging treatment are referred to as “heat-treatable aluminum alloys” [ 6 , 7 ]. In contrast, the aluminum alloys that cannot be strengthened through heat treatment and can be effectively strengthened through work hardening are described as “non-heat-treatable aluminum alloys” [ 6 , 8 ].…”

“…It can be seen that the temper and chemical compositions of age-hardening aluminum alloys have a great influence on their mechanical properties. This is due to the different thermally treated processes and chemical compositions, which affect the characteristics of the precipitation phase, such as the type, quantity, shape, size and distribution [ 7 ]. The characteristics of the precipitation phase can affect the strengthening effect of age-hardening aluminum alloys and thus influence their mechanical properties.…”

“…The age-hardening aluminum alloy in the peak-aged state has high strength owing to a large number of precipitates that are very fine and coherent, and contributes to the effective resistance to dislocation movement and can cause an intense strengthening effect [ 13 , 14 ]. However, when the coherent, metastable precipitates gradually convert to the semi-coherent metastable phase or non-coherent equilibrium phases and are coarsened quickly, the strengthening effect dramatically declined, and the age-hardening aluminum alloy is then in an over-aged state [ 7 ].…”