Superplastic 5083 Aluminum Alloy Sheet ALNOVI†-1 was Approved by Airbus

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Furukawa Review, No. 26 2004 60 2. SUPERPLASTIC FORMING
2.1 Superplastic Phenomenon
While ordinary aluminum alloys elongate by less than
about 100 % even when deformed at high temperatures,
some materials with suitable microstructure exhibit
high elongation strain ranging from several hundreds
to one thousand percent when deformed under
specified conditions. Such a phenomenon is called
“superplasticity”.
Superplastic aluminum alloys generally have very
fine grain structure of about 10 μm in diameter, where
the grain refinement is achieved by optimizing the
kind and amount of additional elements suppressing
grain growth and by controlling the thermo-mechanical
process. Superplastic behavior occurs when these
alloys are deformed at high temperatures of 400~550
˚C with a relative strain rate of 10–4~10–3/s. Because
grain boundary sliding during deformation becomes
significantly activated under these conditions, these
alloys exhibit an extremely large degree of ductility.
In addition, since the flow stress at high temperatures
is very low due to fine grain structure, superplastic
aluminum alloys can be blown-formed just like plastics
with a low pressure of several atmospheres.
2.2 Features of Superplastic Forming
1) Even products which are usually formed in several
parts separately can be integrally formed as a single
part through superplastic forming. The single-piece
forming minimizes the number of parts and joints,
and thus leads to weight and cost savings.
2) Since the forming needs only the female die,
investment cost for dies is reduced.
3) The high formability expands the possibility of
product design.
4) Because of high temperature forming, excellent
form-frozenness is given. But, it is necessary to take
into account thermal contraction.
5) Superior transferability of the die surface to the metal
sheet is provided.
6) Surface defects accompanied by cold press-forming
such as Lüders line and surface roughening do not
arise.
7) Superplastic forming takes longer time than cold
press-forming. It is suitable, accordingly, not for
1. INTRODUCTION
Weight saving is the most important requirement in
the area of aircraft industry. High-strength superplastic
aluminum alloys such as 2004-alloy (Al-Cu system) and
7475-alloys (Al-Zn-Mg-Cu system) have long been used
for aircraft components. However, following points are
the shortcomings of these alloys; 1) it is very expensive
to manufacture the alloy sheets, 2) solution treating and
subsequent aging are indispensable for strengthening
the formed products and 3) corrosion resistance and
weldability are insufficient.
On the other hand, 5000-series alloys (Al-Mg system)
are widely used in various applications because they
have moderate strength, good corrosion resistance,
favorable weldability and ease of surface treatment. The
Research Laboratory in Furukawa-Sky Aluminum Co.
developed “ALNOVI-1” with excellent superplasticity
t h r o u g h o p t i m i z i n g t h e a l l o y c o m p o s i t i o n a n d
manufacturing processes of 5083-alloy, which has
been widely used for structural materials with medium
strength. Being somewhat inferior in superplasticity to
conventional high-strength superplastic aluminum alloys,
the “ALNOVI-1” is more advantageous in manufacturing
cost and exhibits about 300 MPa in strength without heat
treatment after superplastic forming. Typical applications
of the “ALNOVI-1” had been automotive and building
parts rather than aircraft components.
In 2001, Superform Aluminum in UK, a leading
company in superplastic forming, made a prototype
of landing lamp drum assembly for aircraft from the
“ALNOVI-1” sheet by high-temperature blow forming.
Airbus S.A.S., which has a 50 % share of the aircraft
manufacturing market in the world, was very interested in
the alloy sheet and appointed it as a candidate material.
Then the Fukaya Works and the “ALNOVI-1” acquired the
manufacturing factory and product approvals from Airbus
S.A.S.
Superplastic 5083 Aluminum Alloy Sheet “ALNOVI†-1”
was Approved by Airbus
NNeeww PPrroodduuccttss
† ALNOVI is a registered trademark of Furukawa-Sky
Aluminum Corp.
Furukawa Review, No. 26 2004 61
Superplastic 5083 Aluminum Alloy Sheet “ALNOVI-1” was Approved by Airbus
have already participated in the A380 program for an
ultrahigh-capacity aircraft.
This is the first time that superplastic 5000 aluminum
alloys are applied for aircraft parts, and it is expected that
the demand expands during the course of strengthening
the cooperative relationship between Airbus S.A.S. and
Japanese corporations.
[Properties of ALNOVI-1]
Chemical compositions (mass%)
Mg Mn Cr Fe Si Al
4.5 0.7 0.12 < 0.1 < 0.1 Bal
Mechanical properties
Tensile strength
(N/mm2)
Proof strength
(N/mm2)
Elongation
(%)
Fatigue strength
107 (N/mm2)
310 160 28 150
Formability
Superplastic elongation (%) m-value
300 0.5
[Manufacturing Limits of ALNOVI-1]
Original sheet
Thickness: 0.3~3.0 mm
Width: 2000 mm, maximum
Length: 9500 mm, maximum
* Thermal refining is usually “H18”.
* Please ask us for other sizes.
Formed product
Width: 1000 mm, maximum
Length: 2150 mm, maximum
Depth: 250 mm, maximum
* The manufacturing limits for formed products depend
on the forming machine. Please ask us for details.
For more information, please contact:
Technical Research Center, Furukawa-Sky Aluminum
Corp.
1351 Uwanodai, Fukaya-city, Saitama 366-3511, JAPAN
TEL: +81-48-572-1318 FAX: +81-48-573-4418
Sky Aluminum Products Corp.
1351 Uwanodai, Fukaya-city, Saitama 366-3511, JAPAN
TEL: +81-48-571-0004 FAX: +81-48-572-1361
quantity production but for production of high-value
added parts or small- to medium-lot parts ranging
from 50 to 10000 pieces.
8) Cavity defects are liable to be generated by blow
forming. Too much cavity decreases the static and
fatigue strengths of the products.
Blowing pressure:
5 kgf/cm2
Temperature: 500˚C
Brought out
Ceiling plate
Die
Superplastic material
Formed product
Figure 1 Illustration of typical superplastic forming.
2.3 Major Uses of ALNOVI-1 Hitherto
• Body panel and optional parts for automobiles
• Fuel tank for two-wheeled vehicles
• Leisure boat
• Floor sheet and interior panel for vehicles
• Exterior wall, interior wall, ceiling and access floor
sheets for buildings
• Door, gate and fence for residence
• C a s i n g o f e l e c t r o n i c e q u i pme n t f o r me d i c a l
applications
• Ornaments, craftworks, etc.
3. APPROVAL BY AIRBUS
In March 2002, the Fukaya Works of Furukawa-Sky
Aluminum underwent a preliminary inspection. The next
month, Airbus inspectors came from UK and examined
the factory and quality management system officially. In
June, we obtained the factory approval. We prepared
a quality management manual for material production,
and then acquired the material approval for “ALNOVI-1”
in May 2003. In November of the year, we press released
that “ALNOVI-1” was approved as a material for the
landing lamp drum assembly for Airbus A330/A340.
Recently, three Japanese corporations joined the
A300/A340 program, while fifteen Japanese corporations