Super plastic Forming and Diffusion bonding in Aerospace industries

SUBMITTED TO
Dr. Mamadou S Y
Presented by :
Nastaran Zamani -6227546
Rohit Katarya -6306160
Hamid Reza -6406564
Gaurav Maniyar -6244653

Introduction
 The first recorded laboratory observation of what was almost
certainly SP deformation was published in 1912 by Bengough.
 The first really implementation of SPF/DB was Boeing F15 Eagle,
Eurofighter afterwards and Sanders and Ramulu (2004).
 SPF/DB form more complex parts than possible with hot forming.
 Designers and researchers have exploited titanium’s natural ability
to be superplastically formed and diffusion bonded at elevated
temperatures and low strain rates to produce components
 The addition of Mg and Al–6%Cu alloy proved to be the inventive
step that made commercially useful superplastic components a
reality.

Superplasticity
•Superplasticity is the ability of specific polycrystalline materials to
endure extensive tensile plastic deformation.
•Superplastically deformed material gets thinner in a very uniform
manner, rather than forming a “neck” which leads to fracture.
•Numerous metallic materials can show elongations of 500–1000% or
more.
•A material is normally considered to be SP when it has
an m value ≥ 0.3 (where m is strain rate sensitivity of flow stress).

Superplastic Forming
Heating the sheet
until it starts
behave
superplastically
Placing the
starting
sheet
Between
upper and
lower dies
Applying
pressure to
form the sheet

Diffusion Bonding Process
Diffusion Bonding is a solid-state joining process between two
metals in the way that the microstructure and mechanical behavior of
the bond becomes identical to the parent material.
 Elevated Temperature
 Applying pressure for
intimate contact
 Deforming and plastic
flow of microstructural
particles
 Grain formation in the
bond-line

Superplastic materials and
alloys
 Titanium alloys:
-Ti-6Al-4V - AISI 304 stainless steel
-Ti SP-700 alpha-beta alloys
 Aluminum alloys:
-AA5083 ALNOVI-1(s Al–4.5 Mg, 0.7
Mn, 0.12 Cr)
-6-Al-4V alloy
o Magnesium alloys
-AZ31 magnesium alloy

Combination of SPF and DB
 Single-Sheet
 Multi-Sheet
-Two Sheet
-Three-Sheet
-Four Sheet
Types of SPF/DB Process:
•Pressure is applied on opposite faces.
•The applying pressure with respect to temperature should be in a
range of which metals still act as a superplastic material.
•After that, diffusion bonding due to high pressure and temperature
will occur in sections that need to be adhered
•According to complexity various methods are going to use for
SPF/DB processing of metals.

Single-Sheet ( SPF/DB Process )
Demonstration of single-sheet forming
using Superplastic forming
•Die and sheet are maintained at the
same temperature within a heating
press.
•The gas pressure is imposed over the
sheet causing the sheet to form into the
lower part of the die.
•The process progresses further until
the deformed sheet makes contact with
the lower die cavity.
•A diffusion barrier such as boron
nitride is used on the surface to avoid
sticking.

Multi-sheet: ( SPF/DB Process )
a) Two sheet and blow forming and Diffusion Bonding
b) Manufactured Aircraft component of two-sheet
SPF/DB
Figure (a) Figure (b)
Two sheet
•Two- sheet diffusion
bonding is to apply ‘‘stop-
off’’ between the sheets in
the areas where stiffeners
are required in the final
product.

Three-Sheet ( SPF/DB Process )
Example of the 3-sheet structure
(a).Steps For Three
sheet process
•For three (or more) sheet structures, gas pressure
forms the outer sheets (the skin) and the center
sheet(s) are stretched into a core configuration.
•Stop-off acting as a diffusion barrier is deposited
onto areas where no bonding is required

Four Sheets ( SPF/DB Process )
(b). Example of Multisheet

Applications of SPF/DB in
Aerospace Industry
(A)Aeroengine
(B)Northrop B 2
Sprit Bombarder

Aerospace Industry
 Major SPF/DB development initiated 30
years ago was the Rolls-Royce hollow,
wide-chord fan blade.
 Trent series turbofans and provides
almost 50% weight saving.
 The use of titanium provided the final
product with excellent fatigue resistance,
low weight and corrosion resistance.
 The blades are manufactured from
external Ti panels with a central Ti-
membrane sheet with use of stop off.
 Precision dies are used for to develop
internal corrugations and external
aerodynamic shape
Figure(a) Wide –
Chord fan blade

Aerospace Industry
Figure (b)
Titanium Fuselage
part in Aviation
•The use of SPF/DB titanium for the
aft fuselage resulted in 726 fewer
components
•10,000 fewer fasteners
•Achieved 15% weight savings over
the previous process.

Aerospace Industry
•The Ai-Li based alloy used in several
applications on military aircraft was
probably the first to be used in
component manufacture.
•But this alloy was found to have rather
low impact resistance.
•Third generation’ Al–Li based alloys are
now under development.
Figure (b)Military
Aircraft Structure
door

Inspection and Testing Methods
of SPF/DB Parts
 The quality of a diffusion bond joint can be evaluated using NDT
and/or metallographic examination.
 Ultrasonic testing is able to detect quite large voids.
 X-ray radiography can be used on relatively thin sections.
 The most discriminating test of the quality of bonds produced in
thick sections is impact testing
 For bonds formed in sheet materials where impact testing is not
applicable, constrained tensile and compressive lap shear tests are
used.
 Resistance to “hot peel” is an important practical test for evaluating
the quality of DB between thin sheets.

Inspection and Testing Methods
of SPF/DB Parts
Ultrasonic inspection and damages internal
rib in X-Ray inspection

Methods for improving quality of
SPF/DB ( Reducing defects )
 Clean sheet surface pure of abrasive particles.
 Providing inert atmosphere and vacuuming air
between sheets
 Sufficient pressure
 Sufficient time
 Proper temperature
 Using small grain size materials

Advantages of SPF/DB process
 Ability to produce complex monolithic components in
one process
 Eliminating the number of fasteners and assembly
 Reducing weight
 Eliminating limitation in geometry
 Forming brittle alloys or alloys which are difficult to
form with other methods
 Accurate dimensions and excellent mechanical
properties
 No residual stresses or spring-back
 Low stress acting on tooling and increasing tool’s life
 Repeatability of the process

Disadvantages of SPF/DB
process
 Various parameter should be considered like
temperature, pressure, time , etc.
 High energy consumption
 Thermal damage of tooling
 Expensive dies and equipment

Conclusion
 In the presented study, we have shown that
manufacturing and tooling approaches for forming
of parts have been developed that allow complex
compound surfaces to be formed in shapes that
have never been possible using other technologies,
especially for structures that are subjected to
extreme temperatures and high loading conditions.

Super plastic Forming and Diffusion bonding in Aerospace industries

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Super plastic Forming and Diffusion bonding in Aerospace industries