Y alloy
Y alloyis anickel-containingaluminium alloy.It was developed by the BritishNational Physical LaboratoryduringWorld War I,[1]in an attempt to find an aluminium alloy that would retain its strength at high temperatures.[2]
Duralumin,an aluminium alloy containing 4%copperwas already known at this time.[3]Its strength, and its previously unknownage hardeningbehaviour had made it a popular choice forzeppelins.Aircraft of the period were largely constructed of wood, but there was a need for an aluminium alloy suitable for making engines, particularlypistons,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.[4]Like duralumin, this was a 4% copper alloy, but with the addition of 2% nickel and 1.5%magnesium.[4]This addition of nickel was an innovation for aluminium alloys. These alloys are one of the three main groups of high-strength aluminium alloys, thenickel–aluminium alloyshaving the advantage of retaining strength at high temperatures.
The alloy was first used in thecastform, but was soon used forforgingas well. One of the most pressing needs was to develop reliable pistons for aircraft engines. The first experts at forging this alloy werePeter Hooker LimitedofWalthamstow,who were better known as The British Gnôme and Le Rhône Engine Co.[5]They license-built theGnomeengine and fitted it with pistons of Y alloy, rather than their previouscast iron.[5]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.[6]Frank Halfordusedconnecting rodsof this alloy for hisde Havilland Gipsyengine, but these other uses failed to impressRod Banks.[5]
Air MinistrySpecification D.T.D 58A of April 1927 specified the composition and heat treatment of wrought Y alloy.[7]The alloy became extremely important for pistons, and for engine components in general, but was little used for structural members ofairframes.[7]
In the late 1920s, further research on nickel-aluminium alloys gave rise to the successfulHiduminiumor "R.R. alloys", developed byRolls-Royce.[8][9]
Alloy composition
[edit]| Composition[2] | |
|---|---|
| Aluminium | 92.5% |
| Copper | 4.0% |
| Nickel | 2.0% |
| Magnesium | 1.5% |
Heat treatment
[edit]As for many of the aluminium alloys, Y alloyage hardensspontaneously at normal temperatures aftersolution heat treating.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.[2]Theprecipitation hardeningthat takes place during this ageing forms precipitates of both CuAl2and NiAl3.[4]
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 castingis favoured oversand castingas this gives a finer structure that is more amenable to heat treatment.[4]
References
[edit]- ^FJ Camm(January 1944). "Y alloy".Dictionary of Metals and Alloys(3rd ed.). p. 128.
- ^abcRollason, E.C. "Y alloy".Metallurgy for Engineers.Edward Arnold. pp. 277–279.
- ^FJ Camm(January 1944). "Duralumin".Dictionary of Metals and Alloys(3rd ed.). p. 42.
- ^abcdHiggins, Raymond A. (1983). "Part I: Applied Physical Metallurgy".Engineering Metallurgy(5th ed.). Hodder & Stoughton. pp. 435–438.ISBN0-340-28524-9.
- ^abcBanks, Air Commodore F.R. (Rod)(1978).I Kept No Diary.Airlife. p. 63.ISBN0-9504543-9-7.
- ^Banks, I Kept No Diary,p. 69
- ^abMurphy, A.J. (1966). "Materials in Aircraft Structures".J. Royal Aeronautical Society.70(661): 117.doi:10.1017/S0001924000094021.ISSN0368-3931.
- ^FJ Camm(January 1944). "Hiduminium".Dictionary of Metals and Alloys(3rd ed.). p. 58.
- ^FJ Camm(January 1944). "R.R. Alloys".Dictionary of Metals and Alloys(3rd ed.). p. 102.