Common Phases for Aluminum Alloys

A cubic precipitate, which originates from the Al-Mn-Si ternary system, aka τ9, Al15Mn3Si2, Al16Mn4Si3 or Al15Mn4Si2. Mn can be substituted by Fe, as well as Cr and Mo. The phase observed in aluminum alloys is also designated as α.

An iron aluminide, which often forms as a primary phase during casting, aka Al3Fe.

The so-called θ-Al2Cu phase that forms in many Cu-containing aluminum alloys.

Ω-Al2Cu, a metastable precipitate and the coherent version of the θ phase

A semi-coherent precipitate with a stoichiometry of Al2Cu in α-(Al).

Coherent metastable precipitates in α-(Al), also referred to as GPII zones. It has a stoichiometry close to Al3Cu.

Metastable precipitate β’’ related to Mg2Si that forms in Al-Mg-Si based alloys. It may contain Al atoms (Al2Mg5Si4) or be Al-free (Mg5Si6).

Metastable precipitate β' related to Mg2Si, aka Mg9Si5/Mg1.8Si

An Al-containing pre-β Al-Mg-Si metastable precipitate, U1_Al2MgSi2

An Al-containing pre-β Al-Mg-Si metastable precipitate, U2_Al4Mg4Si4

A quaternary phase, aka Al8FeMg3Si6, Q, PHI and H_PHASE

A common Al-Mn compound that forms in Mn-containing aluminum alloys. Mn could be substituted by Cu and Fe, especially to a larger extent by the latter.

An Al-Cu-Mn intermetallic phase that forms in aluminum alloys

A stable Al-Cu-Mg-Si quaternary phase, aka Q, Al5Cu2Mg8Si6, Al3Cu2Mg9Si7 and Al4Cu2Mg8Si7

The coherent / semi-coherent version of Q_ALCUMGSI

Mg2Si, which forms in Mg- and Si-containing aluminum alloys

A common Al-Fe-Si ternary phase in aluminum alloys, aka τ6, Al5FeSi, β-AlFeSi

A common Al-Fe-Si ternary phase in aluminum alloys, aka τ5, α-AlFeSi

An Al-Cu-Fe ternary compound that may form in some aluminum alloys

Si, as well as C and Ge

A common stable precipitate in 7000 series aluminum alloys, aka. the η (MgZn2) phase, eta and the M phase. This phase includes all MgZn2-type phases.

The metastable η' phase, which is related to the η-MgZn2 phase.

A stable phase in Al-Mg-Zn, Al-Cu-Mg and Al-Cu-Mg-Zn. It is modeled as (Al,Cu,Zn)49Mg32 and is often designated as Al2Mg3Zn3 in aluminum alloys.

The metastable form of T phase, T’

The S phase, Al2CuMg

The metastable S’ phase, precursor to the S phase