Thixoforming : Semi-solid Metal Processing

Table 4.3 Properties of selected Al–Li–X alloys relevant to SSM
processing; calculations made by Scheil–Gulliver approximation.
Alloy
Cu
(wt%)
The important key parameters on the basis of the thermochemical calculations are
summarized in Table 4.3.
4.4.2
Choice of a Suitable Basis System
4.4 Development of Aluminium–Lithium-Alloys for Semi-solid Processingj123
Li
(wt%)
Mg
(wt%)
T 50
( C) dfl/dT
T 50 T s
( C)
Intermetallic
phases
A1 (AA2090) 2.5 2.5 — 637 0.023 105 4.7% T2, 1%T1
A2 4.0 2.5 — 629 0.015 97 4.8%T 2, 2.7%T 1, 0.3% T B
A3 4.0 4.0 — 605 0.008 39 12.5% T2, 0.6% AlLi
A4 4.0 1.3 — 639 0.024 107 2.5% T 1, 2.1% T B
A5 (AA8090) 1.2 2.5 0.7 638 0.026 197 3.3% T2, 0.5% AlLi, 0.4% t
A6 — 2.5 4.0 613 0.012 155 5.2% t, 2.7% g
A7 — 4.0 8.0 542 0.004 84 15.5% t, 5.9% g, 1.1% AlLi
A8 (AA1420) — 2.1 5.5 603 0.010 145 3.4% t, 5.2% g
Since for semi-solid workability the formation of a globulitic microstructure is a
prerequisite quench tests were carried out from the partially liquid range. The average
solid phase particle diameter should be less than 100 mm in this respect. The grain
structure formations indicate that the grain-refined alloys A1, A2, A4 and A5 formed
thelargerglobulitic particleswith virtuallyidentical solid phasecontents.ThealloysA3,
A6, A7 and A8 on the other hand display the desired grain sizes (