Guide to Nickel Aluminium Bronze for Engineers

Guide to Nickel Aluminium Bronze for Engineers

Guide to Nickel Aluminium Bronze for Engineers
Ivan Richardson, edited by Carol Powell
Copper Development Association Publication No 222 January 2016 Acknowledgements: Copper Development Association would like to acknowledge the assistance of John Bailey, Roger Francis, John Galsworthy, Dominic Meigh, Carol Powell, Ladji Tikana, Clive Tuck and Peter Webster in the production of this publication.
Copper Development Association is a non-trading organisation that promotes and supports the use of copper based on its superior technical performance and its contribution to a higher quality of life. Its services, which include the provision of technical advice and information, are available to those interested in the utilisation of copper and copper alloys in all their aspects. The Association also provides a link between research and the user industries and is part of an international network of trade associations, the Copper Alliance™. Disclaimer Whilst this document has been prepared with care, we can give no warranty regarding the contents and shall not be liable for any direct, incidental or consequential damage arising out of its use. For complete information on any material, the appropriate standard should be consulted. Copyright © 2016. Copper Development Association
Cover page images: Adjustable bolted propeller – one of two 33 tonne propellers from the Queen Elizabeth class aircraft carrier capable of producing 40 MW of thrust (Courtesy Rolls Royce Marine) Nickel aluminium bronze window frames, cladding and roof, Portcullis House, London Seawater pipe sections (Courtesy Inoxyda SA, France)
2 | GUIDE TO NICKEL ALUMINIUM BRONZE FOR ENGINEERS

Contents

1.0 Introduction...............................................5
2.0 Overview.....................................................6
2.1 Typical Mechanical and Physical Properties................7 2.2 Seawater Corrosion Behaviour.........................................8 2.3 Development Chronology...................................................8
3.0 Applications..............................................10
3.1 Aerospace................................................................................10 3.2 Architecture............................................................................11 3.3 Marine.......................................................................................11
3.3.1 Defence....................................................................11 3.3.2 Commercial............................................................13 3.4 Offshore Oil/Gas and Petrochemical............................14 3.4.1 Bearing Applications within Oil Rig
Equipment..............................................................15 3.4.2 Communications and Transponders............17 3.4.3 Actuator Valves....................................................18 3.4.4 Oil Tankers..............................................................18 3.5 Desalination and Water Condenser Systems............19
4.0 Alloying Elements and Microstructural Phases............................21
4.1 Influence of Alloying Elements.......................................21 4.1.1 Aluminium..............................................................21 4.1.2 Manganese.............................................................21 4.1.3 Nickel........................................................................21 4.1.4 Iron............................................................................21 4.1.5 Impurities...............................................................21
4.2 Types of Microstructural Phases....................................21
5.0 Properties................................................. 26
5.1 Mechanical Strength...........................................................26 5.2 Low and High Temperature Properties........................27 5.3 Impact Toughness................................................................27 5.4 Fatigue Strength...................................................................28 5.5 Creep Strength......................................................................29 5.6 Magnetic Permeability.......................................................30
6.0 Corrosion Resistance.............................. 32
6.1 Protective Surface Film......................................................32 6.1.1 Oxidation at Elevated Temperatures...........32
6.2 Pitting.......................................................................................32 6.3 Crevice Corrosion.................................................................32 6.4 Selective Phase Corrosion.................................................33 6.5 Galvanic Corrosion..............................................................34 6.6 Biofouling................................................................................36 6.7 Electrical Leakage (Stray Current) Corrosion............37 6.8 Sulphide Pollution................................................................37

6.9 Comparative Corrosion Resistance of Various Copper-based Alloys in Seawater Applications.......38
6.10 Erosion Corrosion.................................................................39 6.11 Cavitation................................................................................39 6.12 Stress Corrosion Cracking.................................................40 6.13 Corrosion Fatigue.................................................................41 6.14 Comparison in Seawater with Other Alloy
Groups......................................................................................43 6.15 Corrosion Resistance of Nickel Aluminium
Bronze in Chemical Environments................................44 6.15.1 Sulphuric Acid......................................................44 6.15.2 Acetic Acid.............................................................44 6.15.3 Hydrochloric Acid................................................44 6.15.4 Phosphoric Acid...................................................44 6.15.5 Hydrofluoric Acid................................................45 6.15.6 Nitric Acid...............................................................45 6.15.7 Alkalis.......................................................................45 6.15.8 Salts..........................................................................45 6.15.9 Other Corrosive Chemical
Environments........................................................45 6.16 Weld Areas..............................................................................46
6.16.1 Galvanic Corrosion.............................................46 6.16.2 Selective Phase Attack......................................46 6.16.3 Stress Corrosion...................................................46 6.16.4 Porosity and Gas Inclusions............................46
7.0 Heat Treatment....................................... 47
7.1 Stress Relieving..........................................................................47 7.2 Annealing......................................................................................47 7.3 Quenching and Tempering....................................................48 7.4 Heat Treatment of Cast CuAl10Fe5Ni5.............................49 7.5 Heat Treatments in International Standards.................50
8.0 Wear and Galling Performance............. 52
8.1 Fretting Wear..............................................................................53 8.2 Galling............................................................................................54
9.0 Fabrication and Manufacture............... 56
9.1 Welding....................................................................................56 9.1.1 Welding Processes.................................................57 9.1.2 Joining Processes...................................................57 9.1.3 Recommended Welding Processes.................57 9.1.3.1 TIG/GTAW Process..............................57 9.1.3.2 MIG/GMAW Process..........................58 9.1.3.3 Manual Metal Arc..............................59 9.1.3.4 Electron Beam Welding...................60 9.1.3.5 Friction Welding.................................60 9.1.3.6 Laser Welding......................................60 9.1.4 Welding Practice and Joint Design.................60 9.1.4.1 Design of Joints..................................60 9.1.4.2 Weld Preparation................................61

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Contents

Appendix

9.1.5 Pre-heating and Weld Run Temperature Control...........................................62
9.1.6 Selection of Filler Materials for TIG/GTAW and MIG/GMAW Welding............63
9.1.7 Post Weld Heat Treatment................................63 9.1.7.1 Stress Relief.........................................63 9.1.7.2 Full Anneal...........................................63
9.2 Machining..............................................................................65 9.2.1 Rough and Finishing Turning..........................67 9.2.2 Milling.......................................................................68 9.2.3 Slot Milling..............................................................69 9.2.4 Threading................................................................. 70
9.3 Mechanical and Non-destructive Testing................. 71 9.3.1 Mechanical Testing.............................................. 71 9.3.2 Non-destructive Testing.................................... 71
9.4 Manufacture - Casting Processes................................72 9.4.1 Modern Casting Techniques.............................72 9.4.2 Continuous Casting Computer Simulation..........................................73 9.4.3 Continuous Casting.............................................73 9.4.4 Centrifugal Casting..............................................75
9.5 Wrought Hot Working Processes..................................76 9.5.1 Hot Working Ranges...........................................76 9.5.2 Cold Working..........................................................76 9.5.3 Extrusion..................................................................76 9.5.4 Rolling.......................................................................76 9.5.5 Forging......................................................................77
10.0 Summary Guidelines for Engineers....... 79
11.0 References and Further Information.... 80
11.1 General References.............................................................80 11.2 Publications from Copper Development
Association (CDA) ............................................................... 81 11.3 Other Publications..............................................................81

Appendix: Tables 1-22.................................... 82

Standards, Designations, Chemical Compositions and Mechanical Properties

International Standards

Table App1

Nickel Aluminium Bronze - Wrought..............83

Table App2

Nickel Aluminium Bronze – Cast.......................85

UK: Nickel Aluminium Bronze - Wrought

Table App3

Chemical Compositions.........................................86

Table App4

Mechanical Properties...........................................86

UK: Nickel Aluminium Bronze – Cast

Table App5

Chemical Compositions.........................................87

Table App6

Mechanical Properties...........................................87

UK/European: Nickel Aluminium Bronze – Wrought

Table App7

Chemical Compositions.........................................88

Table App8

Mechanical Properties...........................................89

UK/European: Nickel Aluminium Bronze – Cast

Table App9

Chemical Compositions.........................................90

Table App10

Mechanical Properties...........................................90

France: Nickel Aluminium Bronze – Wrought

Table App11

Chemical Compositions.........................................91

Table App12

Mechanical Properties...........................................91

France: Nickel Aluminium Bronze – Cast

Table App13

Chemical Compositions.........................................92

Table App14

Mechanical Properties...........................................92

Germany: Nickel Aluminium Bronze – Wrought

Table App15

Chemical Compositions.........................................93

Table App16

Mechanical Properties...........................................94

Germany: Nickel Aluminium Bronze – Cast

Table App17

Chemical Compositions.........................................95

Table App18

Mechanical Properties...........................................95

USA: Nickel Aluminium Bronze – Wrought

Table App19

Chemical Compositions.........................................96

Table App20

Mechanical Properties...........................................96

USA: Nickel Aluminium Bronze – Cast

Table App21

Chemical Compositions.........................................97

Table App22

Mechanical Properties...........................................98

4 | GUIDE TO NICKEL ALUMINIUM BRONZE FOR ENGINEERS

1.0 Introduction
Alloys of copper and aluminium are known as aluminium bronze and, together with other alloying additions, produce a range of properties that are beneficial to a diverse range of industries. Of these, the nickel aluminium bronze group of alloys is the most widely used. They have been adapted with time to optimise performance and can provide a combination of properties that can offer an economic alternative to other types of alloy systems. Nickel aluminium bronzes are available in both cast and wrought product forms and have a unique combination of properties:
• Excellent wear and galling resistance • High strength • Density (10% lighter than steel) • Non-sparking • Low magnetic permeability (of <1.03 µ in selected grades) • High corrosion resistance • Good stress corrosion properties • Good cryogenic properties • High resistance to cavitation • Damping capacity twice that of steel • High resistance to biofouling • A protective oxide surface film which has the ability to self-repair. End uses range from landing gear bushing and bearings for all of the world’s commercial aircraft to seawater pumps and valves, propellers for naval and commercial shipping, non-sparking tools in the oil and gas industry and pleasing facades in architecture. The nickel aluminium bronze alloys are fairly complex materials and, during manufacture, require good control of the metal structure by attention to composition and heat treatment. As such it is the purpose of this publication to provide an engineering overview of the properties of the alloys, their specifications and their applications for operators, designers, manufacturers and fabricators. Their corrosion behaviour is explained and guidance is given to obtain optimum service performance. Methods of manufacture, welding and fabrication are also described and a list of references and useful publications is provided. The Appendix covers full details of designations, specifications and related composition and mechanical property requirements.
GUIDE TO NICKEL ALUMINIUM BRONZE FOR ENGINEERS | 5

2.0 Overview

Broadly, the nickel aluminium bronzes can be classified as alloys containing 6-13% aluminium and up to 7% iron and 7% nickel. The more common alloys normally contain 3-6% each of these two elements. Manganese up to approximately 1.5% is also added, both as a deoxidant and a strengthening element. There is a separate family of alloys which contain up to 14% manganese with additions of iron and nickel. They are called here manganese aluminium bronzes and the standard alloy, designated CuMn11Al8Fe3Ni3, is discussed briefly in later sections.
Table 1 below gives an indication of a range of aluminium bronze alloy properties with increasing alloy additions and strength. Alloys CW304G, CW307G and CW308G are nickel aluminium bronzes.

Table 1 - Specification BS EN 12165 Wrought Forgings 6-80 mm Diameter

Alloy

Cu

Al

Fe

Ni

Mn

Si

0.2% Proof

%

%

%

%

%

%

Strength

N/mm² (MPa)

CW305G Rem 9.0-10.0 0.5-1.5

180

CW303G Rem 6.5-8.5 1.5-3.5 1.0 max

180

CW304G Rem 8.0-9.5 1.0-3.0 2.0-4.0

180

CW302G Rem 6.3-7.6

1.5-2.2

250

CW306G Rem 9.0-11.0 2.0-4.0

1.5-3.5

250

CW307G Rem 8.5-11.0 3.0-5.0 4.0-6.0 1.0 max

350

CW308G Rem 10.5-12.5 5.0-7.0 5.0-7.0 1.5 max

450

Tensile Strength N/mm² (MPa)
420 460 500 500 500 650 750

Elongation %
20 30 30 20 20 12 5

Hardness HB
100 110 115 120 120 180 190

Since the first manufacture of aluminium bronze in the 1850s, there has been a progressive development in elemental additions to improve the mechanical properties and corrosion resistance. The early alloys were binary systems of copper and aluminium with aluminium in the range 6-11%. Up to about 8-9% aluminium, the equilibrium metal structure is single phase and progressively increases in strength as the aluminium increases. Such alloys were found to be ductile and suitable for cold worked products. At higher aluminium levels, a second phase occurs in the structure at higher temperatures which, when retained by cooling quickly, is stronger and harder with good corrosion resistance and better erosion resistance. Alloys typically containing 9-10% aluminium became noted for their strength but, as their ductility for forming was better at high temperatures, the two phase alloys were more conveniently hot worked. If slow cooled below 565oC, however, the structure alters again, becoming less ductile and also more susceptible to corrosion in seawater.
By 1914 the temper hardening features of aluminium bronze containing nickel were recognised (1). Its presence, together with iron additions to suppress unwanted structural phases, became fully appreciated over the next decade (2) and now forms the basis of the modern complex alloy systems.

The combined additions of iron and nickel are particularly important as they also improve the strength and corrosion resistance. When both are present at nominally 5%, they modify the structure of 9-10% aluminium alloys beneficially and the properties can be further enhanced by quench and temper heat treatments. These are the most popular type of nickel aluminium bronzes for seawater service and a range of wrought and cast product forms is available.

Aluminium has a strong affinity for oxygen. This is important for the corrosion resistance of the alloys as it plays an important part of the surface protective film, but aluminium oxides can also be present as internal inclusions in the metal and historically these inclusions, together with shrinkage cavities formed when the alloys were cast, prevented their initial commercial development. However, in 1913 Pierre Gaston Durville developed a casting method called the ‘Durville process', which became synonymous with the early production of the alloys. This was a nonturbulent mould tilting process which enabled billet and castings to be produced without the detrimental oxide inclusions. In more recent years, the original ‘Durville process' has been superseded by more economic casting processes such as semi and continuous casting methods, where cooling rates and control of oxide inclusions are more sophisticated. Casting methods are discussed in Section 9.4 and Table 4 gives a chronological development of aluminium bronze alloys.

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2.1 Typical Mechanical and Physical Properties
Although nickel aluminium bronzes now form the largest family of aluminium bronze alloys worldwide, during their development various countries adopted and manufactured their own versions. Whereas European standards attempted to unify this, major world producers - including the USA, Germany, France and the UK - still use their own standards, mainly for aerospace and military marine applications. Tables App1-22 in the Appendix provide full details of international standards and their designations, compositions and mechanical properties. There is some overlap and many specifications can be dual released, particularly in the aerospace sector.
Table 2 illustrates the properties of one of the most common wrought nickel aluminium bronzes. The composition range in UK, European and USA standards overlap. Mechanical properties are given for two standards to indicate how the strength achievable can differ. Further information and data on mechanical properties are given in Section 5.0 and the Appendix.

Table 2 – Properties of Common Wrought Nickel Aluminium Bronzes

Standards

BS EN 12163

ASTM B150

Alloy Designation

CW307G

C63000

AMS 4640 C63000

Composition Ranges

Cu Rem, Al 8.5-11%, Ni 4.0-6.0%, Fe 2.0-5.0%, Mn 1.5% max

Def Stan 02-833 Def Stan 02-833

Physical Properties* Density Melting range Hot working range Thermal conductivity Electrical resistivity Coefficient of linear expansion (20-200°C) Specific heat Magnetic permeability

7590 kg/m³ 1060-1075°C 705-925°C 42 W/m°K 0.13 µΩ.m 17.1 x 10-6/°C 420 J/kg/K 1.5 µ

Mechanical Properties at Room Temperature
0.2% Proof strength Tensile strength Shear strength Vickers hardness Elongation Impact toughness at room temperature Modulus of elasticity Modulus of rigidity Poisson’s ratio Fatigue limit in air 10 7 cycles

Def Stan 02-833* Hot Rolled Bar 50 mm Dia
295 N/mm² (MPa) 635 N/mm² (MPa) 415 N/mm² (MPa)
200 HV 17%
23-27 Joules 125 GPa 49 GPa 0.32
278-293 N/mm² (MPa)

AMS 4640 50 mm Wrought 414 N/mm² (MPa) 758 N/mm² (MPa)
10%

* Data is taken for Def Stan 02-833 from Def Stan 02-879 Part 2, which is not a manufacturing specification for nickel aluminium bronze but contains advisory material property data sheets.

GUIDE TO NICKEL ALUMINIUM BRONZE FOR ENGINEERS | 7

2.2 Seawater Corrosion Behaviour
Nickel aluminium bronze is widely used in seawater systems, particularly as cast valve bodies, pump casings and impellers. Corrosion resistance of the alloys relies on a complex copper-aluminium thin adherent oxide surface film, which acts as a protective barrier and is self-repairing, even down to very low levels of oxygen in the service environment. Of the copper alloys, they have high resistance to flow and a high order of resistance to ammonia stress corrosion cracking. They have excellent resistance to cavitation and are an established alloy for ship propellers.
Selective phase corrosion (also known as de-aluminification) has been observed at crevices and other shielded areas, particularly in cast alloys. This can be avoided by galvanic coupling to less noble alloys or by ensuring exposure to aerated flowing seawater when first immersed in seawater so that protective films in surrounding areas become established. Selective phase corrosion will be explored again in more detail in Section 6.4.
As with all copper alloys, extended exposure to polluted or putrefied water should be avoided as they experience higher corrosion rates in the presence of sulphides.
Other general corrosion data is given in Table 3. Although specific to UK Defence Standard 02-879, the data is a guide to other specifications within the CuAl10Ni5Fe4 family of alloys.

Table 3 – General Corrosion Data (Full Immersion in Seawater) ex UK Def Stan 02-879 Part 1 Issue 1 (3)

Free corrosion potential Corrosion rate

-0.25 VSCE 0.05-0.075 mm/year

Impingement resistance

Up to 4.3 m/sec

NB: Nickel levels equal or greater than those of iron are believed to increase corrosion resistance

The high manganese aluminium bronze alloy CuMn11Al8Fe3Ni3 is used primarily as cast propellers in marine environments as it has a higher resistance to erosion corrosion (4). However, it has a lower resistance to selective phase corrosion than nickel aluminium bronze and is not advised for static or shielded area crevice conditions.

2.3 Development Chronology

The invention of electromagnetic induction and electrical generators in the 1800s was the catalyst for the rapid development of modern metal processing – see Table 4.

Table 4 – Chronology
1856 An English metallurgist John Percy had observed: “A small proportion of aluminium increases the hardness of copper, does not injure its malleability, makes it susceptible of a beautiful polish and varies its colour from red-gold to pale yellow.”
1856 Aluminium bronze was produced in France by the Tissier brothers of Rouen, but was too expensive to manufacture on a commercial scale.
1885 The Cowles brothers in the USA produced aluminium bronze at a lower cost, with a process using electricity and reducing corundum, an oxide of aluminium with the aid of charcoal in the presence of granulated copper. They also set up a subsidiary in Milton close to Stoke-on-Trent, UK and, between the two companies, they produced six grades of aluminium bronze.
1886 Charles Hall and Paul Héroult, working independently, successfully produced aluminium by an electrolysis process at an economic price, enabling aluminium bronze to be manufactured more commercially.
1887 Héroult took out the first patent for aluminium bronze as an indirect method of producing aluminium by electrolysing alumina as the anode and copper as the cathode.
1887 The commercial production of aluminium bronze by this indirect method was relatively short-lived with the more economic direct production of aluminium by the Pittsburgh Reduction Company at Niagara Falls using the Hall process. The company went on to become Alcoa with the commercial production of aluminium. From this point on manufacturers chose to make their own alloys, which led to a growth in production in the form of castings, forgings and rolled bar.

8 | GUIDE TO NICKEL ALUMINIUM BRONZE FOR ENGINEERS

1893 1894 1910 1913
1914 1923 1928 1934
1937
1937 1939-45
1951 1967 1978
1980 – present

Design engineers at Westinghouse Machine and Air Brake Company in the USA started to use aluminium bronze in corrosion applications.
Alexander Dick invented the copper alloy extrusion press as we know it today and he went on to form the Delta Metal Company in the UK. However, it was not until the 1930s that presses were designed large enough to extrude aluminium bronze (5).
Lantsberry and Rosenhain from the National Physical Laboratory, UK, researched manganese additions, which were found to have a strengthening effect and also acted as a deoxidant.
In France Pierre Gaston Durville set up a company called Bronzes et Alliages Foreables SA in which he used his new patent casting method known as the ‘Durville process’, which went on to revolutionise the production of aluminium bronze billet. The tilting furnace and mould method prevented the turbulent flow of metal which had caused many problems in past production, due to oxide inclusions.
Read and Greaves reported the temper hardening features of aluminium bronze containing 10% aluminium and upwards of 2% nickel (6).
Charles Meigh, after 4 years with the Durville company, set up his own foundry near Rouen in France called Forge et Founderie d’Alliages de Haute Resistance. He modified the Durville process to incorporate a tilting sand mould to the tilting furnace.
Genders, Reader and Foster conducted work on some true complex cast nickel aluminium bronzes, CuAl9Fe6Ni6, CuAl10Fe3Ni3Mn3 (2).
Continuous casting was used for copper alloys when the German Siegfried Junghans invented the reciprocating mould which was used at the Wieland-Werke company. During the same period in the USA, Byron Eldred invented the use of graphite as a mould material, which later went on to become part of the modern continuous casting method for aluminium bronze.
Charles Meigh returned to England and set up a new company called Meigh of Cheltenham, which later became Meigh Castings. He also set the Meigh’s process at Chatham Naval Dockyard, where the British Admiralty had taken a great interest in the use of aluminium bronze for marine applications.
Gough and Sopwith conducted research on fatigue and corrosion fatigue of some special bronzes including forged CuAl10Fe5Ni5 (7).
The onset of the Second World War was a major catalyst for the mass production of the nickel aluminium bronzes with companies such as Meigh’s, Birkett Billington & Newton and Manganese Bronze in the UK, Ampco Metals in the USA and Le Bronze in France producing cast and wrought products.
The first nuclear submarine, USS Nautilus (SSN-571) was built by General Dynamic at their Electric Boat facility at Groton. The boat incorporated nickel aluminium bronze and the design and build was overseen by Admiral Rickover.
The rise in the price of oil and the control by OPEC led to oil exploration offshore in the Gulf of Mexico and the North Sea, which created new demand for nickel aluminium bronze for pumps, valves and fire control equipment.
The deregulation of commercial aerospace regulations in the USA promoted a major growth in low cost airlines. In Europe this was not completed until 1997. However, the outcome of both these processes gave rise to a steady 5-6% year-on-year growth, starting from the boom years of the early 1980s. Both cast and wrought aluminium bronzes were used extensively in the landing bushing and bearings of all commercial world aircraft.
Aerospace, defence, commercial marine and the petrochemical industrial sectors continue to remain the major outlets for nickel aluminium bronze.

GUIDE TO NICKEL ALUMINIUM BRONZE FOR ENGINEERS | 9

3.0 Applications
The nickel aluminium bronzes have six main areas of application:
1) Aerospace 2) Architecture 3) Marine - defence 4) Marine - commercial 5) Offshore oil/gas and petrochemical 6) Desalination and water condenser systems.
3.1 Aerospace
The main application for nickel aluminium bronze in the aerospace sector is landing gear bearings for the world’s fleet of commercial aircraft.
The excellent bearing properties against steel, corrosion resistance in salt conditions during de-icing of runways in winter and high mechanical properties make it an ideal alloy for this application. The main specifications are AMS 4640, AMS 4880, AMS 4881 and AMS 4590, BS2 B 23, NFL14-702, NFL14-705 and NFL14-706 (see Tables App1-22 in the Appendix).
The aircraft companies and main subcontractors also have their own specifications, for example Airbus ASN-A 3406, ASN-A 3315, ASN-A6127A and Rolls Royce MSRR 8503.
Figure 1 illustrates the range of bearings and bushing used in aircraft landing gears. Figure 2 demonstrates landing gears being examined after a set number of flying hours or landings.

Figure 1 - Landing gear and wing flap bearings

Figure 2 - Routine maintenance of landing gear

In addition to landing gear bearings, applications include wing flap bearings, door hardware, wheel bearings, hydraulic actuators, valves, steering joints and helicopter controls.
In general, alloys C63000 to AMS 460, AMS 4880 or BS2 B 23 are used for the majority of the landing gear applications. For high load and greater wear requirements, the cast AMS 4881 and wrought AMS 4590 can be used (see Appendix).

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