Y alloy
Encyclopedia
Y alloy is a nickel
-containing aluminium alloy
. It was developed by the National Physical Laboratory during World War I
, in attempt to find an aluminium alloy that would retain its strength at high temperatures.
Duralumin
, an aluminium alloy containing 4% copper
was already known at this time. Its strength, and its previously unknown age hardening behaviour had made it a popular choice for zeppelin
s. Aircraft of the period were largely constructed of wood, but there was a need for an aluminium alloy suitable for making engines, particularly piston
s, that would have the strength of duralumin but could retain this when in service at high temperatures for long periods.
The National Physical Laboratory began a series of experiments to study new aluminium alloys. Experimental series "Y" was successful, and gave its name to the new alloy. Like duralumin, this was a 4% copper alloy, but with the addition of 2% nickel and 1.5% magnesium
. This addition of nickel was an innovation for aluminium alloys. These alloys are one of the three main groups of high-strength aluminium alloys, the nickel-aluminium alloys having the advantage of retaining strength at high temperatures.
The alloy was first used in the cast
form, but was soon used for forging
as well. One of the most pressing needs was to develop reliable pistons for aircraft engines. The first experts at forging this alloy were Peter Hooker Ltd. of Walthamstow
, who were better known as The British Gnôme and Le Rhône Engine Co.. They license-built the Gnôme
engine and fitted it with pistons of Y alloy, rather than their previous cast iron
. These pistons were highly successful, although impressions of the alloy as a panacea suitable for all applications were less successful; a Gnôme cylinder in Y alloy failed on its first revolution. Frank Halford
used connecting rod
s of this alloy for his de Havilland Gipsy
engine, but these other uses failed to impress Rod Banks
.
Air Ministry
Specification D.T.D 58A of April 1927 specified the composition and heat treatment of wrought Y alloy. The alloy became extremely important for pistons, and for engine components in general, but was little used for structural members of airframe
s.
In the late 1920s, further research on nickel aluminium alloys gave rise to the successful Hiduminium
or "R.R. alloys", developed by Rolls-Royce
.
. The heat treatment is to heat it to 500 to 520 °C (932 to 968 F) for 6 hours, then to allow it to age naturally for 7–10 days. The precipitation hardening that takes place during this ageing forms precipitates of both CuAl2 and NiAl3.
The times required depend on the grain structure of the alloy. Forged parts have the coarsest eutectic masses and so take the longest times. When cast, chill casting is favoured over sand casting
as this gives a finer structure that is more amenable to heat treatment.
Nickel
Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
-containing aluminium alloy
Aluminium alloy
Aluminium alloys are alloys in which aluminium is the predominant metal. The typical alloying elements are copper, magnesium, manganese, silicon and zinc. There are two principal classifications, namely casting alloys and wrought alloys, both of which are further subdivided into the categories...
. It was developed by the National Physical Laboratory during World War I
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...
, in attempt to find an aluminium alloy that would retain its strength at high temperatures.
Duralumin
Duralumin
Duralumin is the trade name of one of the earliest types of age-hardenable aluminium alloys. The main alloying constituents are copper, manganese, and magnesium. A commonly used modern equivalent of this alloy type is AA2024, which contains 4.4% copper, 1.5% magnesium, 0.6% manganese and 93.5%...
, an aluminium alloy containing 4% copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
was already known at this time. Its strength, and its previously unknown age hardening behaviour had made it a popular choice for zeppelin
Zeppelin
A Zeppelin is a type of rigid airship pioneered by the German Count Ferdinand von Zeppelin in the early 20th century. It was based on designs he had outlined in 1874 and detailed in 1893. His plans were reviewed by committee in 1894 and patented in the United States on 14 March 1899...
s. Aircraft of the period were largely constructed of wood, but there was a need for an aluminium alloy suitable for making engines, particularly piston
Piston
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from...
s, that would have the strength of duralumin but could retain this when in service at high temperatures for long periods.
The National Physical Laboratory began a series of experiments to study new aluminium alloys. Experimental series "Y" was successful, and gave its name to the new alloy. Like duralumin, this was a 4% copper alloy, but with the addition of 2% nickel and 1.5% magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
. This addition of nickel was an innovation for aluminium alloys. These alloys are one of the three main groups of high-strength aluminium alloys, the nickel-aluminium alloys having the advantage of retaining strength at high temperatures.
The alloy was first used in the cast
Casting
In metalworking, casting involves pouring liquid metal into a mold, which contains a hollow cavity of the desired shape, and then allowing it to cool and solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process...
form, but was soon used for forging
Forging
Forging is a manufacturing process involving the shaping of metal using localized compressive forces. Forging is often classified according to the temperature at which it is performed: '"cold," "warm," or "hot" forging. Forged parts can range in weight from less than a kilogram to 580 metric tons...
as well. One of the most pressing needs was to develop reliable pistons for aircraft engines. The first experts at forging this alloy were Peter Hooker Ltd. of Walthamstow
Walthamstow
Walthamstow is a district of northeast London, England, located in the London Borough of Waltham Forest. It is situated north-east of Charing Cross...
, who were better known as The British Gnôme and Le Rhône Engine Co.. They license-built the Gnôme
Gnome Monosoupape
The Monosoupape , was a rotary engine design first introduced in 1913 by Gnome Engine Company...
engine and fitted it with pistons of Y alloy, rather than their previous cast iron
Cast iron
Cast iron is derived from pig iron, and while it usually refers to gray iron, it also identifies a large group of ferrous alloys which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy. White cast iron is named after its white surface when fractured, due...
. These pistons were highly successful, although impressions of the alloy as a panacea suitable for all applications were less successful; a Gnôme cylinder in Y alloy failed on its first revolution. Frank Halford
Frank Halford
Major Frank Bernard Halford CBE FRAeS was an English aircraft engine designer.-Career:Educated at Felsted, In 1913 he left the University of Nottingham before graduating to learn to fly at Brooklands and Bristol Flying School and became a flight instructor using Bristol Boxkites.He served in the...
used connecting rod
Connecting rod
In a reciprocating piston engine, the connecting rod or conrod connects the piston to the crank or crankshaft. Together with the crank, they form a simple mechanism that converts linear motion into rotating motion....
s of this alloy for his de Havilland Gipsy
De Havilland Gipsy
The de Havilland Gipsy is a British air-cooled 4-cylinder in-line aircraft engine designed by Frank Halford in 1927 to replace the ADC Cirrus in the de Havilland D.H.60 Moth light biplane....
engine, but these other uses failed to impress Rod Banks
Francis Rodwell Banks
Air Commodore Francis Rodwell "Rod" Banks, RAF , CB., OBE., Commander of Legion of Honour , Commander of the Legion of Merit , Military Order of St. Stanislaus , Hon. CGIA., Hon. FRAeS, Hon...
.
Air Ministry
Air Ministry
The Air Ministry was a department of the British Government with the responsibility of managing the affairs of the Royal Air Force, that existed from 1918 to 1964...
Specification D.T.D 58A of April 1927 specified the composition and heat treatment of wrought Y alloy. The alloy became extremely important for pistons, and for engine components in general, but was little used for structural members of airframe
Airframe
The airframe of an aircraft is its mechanical structure. It is typically considered to include fuselage, wings and undercarriage and exclude the propulsion system...
s.
In the late 1920s, further research on nickel aluminium alloys gave rise to the successful Hiduminium
Hiduminium
The Hiduminium or R.R. alloys are a series of high-strength, high-temperature aluminium alloys, developed for aircraft use by Rolls-Royce before World War II. They were manufactured and later developed by High Duty Alloys Ltd....
or "R.R. alloys", developed by Rolls-Royce
Rolls-Royce Limited
Rolls-Royce Limited was a renowned British car and, from 1914 on, aero-engine manufacturing company founded by Charles Stewart Rolls and Henry Royce on 15 March 1906 as the result of a partnership formed in 1904....
.
Alloy composition
| Composition | |
|---|---|
| Copper Copper Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish... |
4.0% |
| Nickel Nickel Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile... |
2.0% |
| Magnesium Magnesium Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole... |
1.5% |
| Aluminium Aluminium Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances.... |
remainder |
Heat treatment
As for many of the aluminium alloys, Y alloy age hardens spontaneously at normal temperatures after solution heat treatingQuench
In materials science, quenching is the rapid cooling of a workpiece to obtain certain material properties. It prevents low-temperature processes, such as phase transformations, from occurring by only providing a narrow window of time in which the reaction is both thermodynamically favorable and...
. The heat treatment is to heat it to 500 to 520 °C (932 to 968 F) for 6 hours, then to allow it to age naturally for 7–10 days. The precipitation hardening that takes place during this ageing forms precipitates of both CuAl2 and NiAl3.
The times required depend on the grain structure of the alloy. Forged parts have the coarsest eutectic masses and so take the longest times. When cast, chill casting is favoured over sand casting
Sand casting
Sand casting, also known as sand molded casting, is a metal casting process characterized by using sand as the mold material.It is relatively cheap and sufficiently refractory even for steel foundry use. A suitable bonding agent is mixed or occurs with the sand...
as this gives a finer structure that is more amenable to heat treatment.