Effects of intermetallic particles on cavitation during superplastic forming of aluminium alloy

In recent years there has been a largely unspoken demand for a high strength, non-heat treatable aluminium alloy for superplastic forming applications. This is particularly true for the automotive industry since the high strength, superplastic aluminium alloys, such as AA7475, are both too time consuming (in forming and heat treatment) and too expensive. Compound this with the expense of corrosion protection and almost all aluminium alloys except for AA5083 fall by the wayside for the automobile industry.However, the need for a higher strength alloy has remained. To achieve this Hydro has systematically investigated the basis behind the superplastic forming of AA5083. On this basis a new high strength 5xxx alloy was extrapolated. The resulting alloy was then characterised and benchmarked against the existing SPF alloy, AA5083. The new alloy, an AA5456-type alloy demonstrated a higher strength than AA5083 while improving the formability and rate of forming. This paper will discuss some of the lessons learned during the development of this alloy.

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Aerospace series. Aluminium alloy AL-P8090-O2. Sheet for superplastic forming (SPF). 0,8 mm ≤ a ≤ 6 mm

10.3403/30065764 ◽

2005 ◽

Keyword(s):

Aluminium Alloy ◽

Superplastic Forming

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Strengthening at High Temperatures in an Iron-Aluminium Alloy by the Precipitation of Stable and Coherent Intermetallic Particles

MRS Proceedings ◽

10.1557/proc-980-0980-ii01-04 ◽

2006 ◽

Vol 980 ◽

Author(s):

David G. Morris ◽

Maria A. Muñoz-Morris ◽

Luis M. Requejo

Keyword(s):

High Temperature ◽

Aluminium Alloy ◽

High Temperatures ◽

Iron Aluminides ◽

Processing Route ◽

High Temperature Strength ◽

Transition Elements ◽

Intermetallic Particles ◽

Strengthening Particles ◽

Low Solubility

AbstractDespite decades of intensive research iron aluminides remain characterised by relatively poor ductility at room temperature and low strength at high temperatures, especially under slow strain rate or creep conditions. A variety of strengthening particles has been tested for improving high temperature strength, but each has serious limitations: typical carbide precipitates are unable to resist dissolution or coarsening at high temperatures; as-solidified iron aluminides with sufficient amounts of transition elements such as Nb or Mo show heavy solidification segregation and are embrittled by a network of Laves phase; mechanical milling with stable oxides appears an excessively expensive processing route. A new iron-aluminium alloy has been developed with Zr and Cr additions that forms fine coherent precipitates even after extended annealing at temperatures as high as 900ºC. These precipitates have a complex Fe3Zr structure and form in a cube-on-cube orientation relationship in the bcc matrix. The low solubility and diffusivity of the solute, as well as the low energy, near-coherent interface ensures excellent stability of these intermetallic precipitates. Interesting strengthening is possible for this material under the relevant high temperature creep conditions.

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