Metal treatment – Compositions – Heat treating
Patent
1990-03-21
1991-05-28
Andrews, Melvyn J.
Metal treatment
Compositions
Heat treating
148159, 148417, 148439, 420534, B22D 2500, C22C 2106
Patent
active
050191780
DESCRIPTION:
BRIEF SUMMARY
This invention relates to an aluminium-silicon alloy article produced by a squeeze forming process and particularly, but not essentially, relates to a squeeze formed aluminium-silicon alloy cylinder liner for an internal combustion engine.
It is known that cylinder liners can be produced by squeeze forming aluminium alloys but, in order to provide adequate wear properties, the internal bores of such liners have hitherto required plating with a nickel-silicon carbide composite coating. Generally, such a coating process adds an unacceptable production cost to such liners.
It has been proposed in GB-A-2085920 of Comalco Limited to utilise a cast aluminium-silicon alloy in the production of various automotive components wherein the alloy has an essentially eutectic microstructure containing not more than 10% of primary alpha-aluminium dendrites and being substantially free from intermetallic particles exceeding 10.mu. in diameter. Further discussion regarding the alloy, the subject of this patent specification, is to be found in SAE Technical Paper Series 840123 and 860558 wherein the alloy, identified by Comalco Limited as 3HA, is described as being castable by gravity, low pressure or high pressure casting methods.
It is to be understood from the above mentioned patent specification and papers that the properties of 3HA alloy are determined by the correct microstructure which in turn is produced by the specific alloy composition and its solidification parameters. For example, in the patent specification it is stated that strengthening of the matrix is enhanced by the presence of stable manganese and zirconium containing particles. It is also stated that titanium, because of its known grain refining characteristics, is added to improve castability and to improve the mechanical properties of the alloy.
We have discovered that articles of an aluminium-silicon alloy having similar desirable characteristics to those of the 3HA alloy can be produced from an alloy melt of a different composition to that of 3HA and with different solidification parameters. Hence it is an object of the present invention to provide a new or improved article of an aluminium-silicon alloy and the method for its production.
In accordance with the invention there is provided a squeeze formed aluminium-silicon alloy article produced from a melt consisting essentially of the following composition by weight:
______________________________________ Silicon 14% to 16%
Copper 1.9% to 2.2%
Nickel 1.0% to 1.4%
Magnesium 0.4% to 0.55%
Iron 0.6% to 1.0%
Manganese 0.3% to 0.6%
Silicon Modifier 0.02% to 0.1%
______________________________________
as-formed article having an essentially eutectic microstructure containing
not more than 10% of primary alpha-aluminium dendrites and being
substantially free from intermetallic particles exceeding 10.mu. in
diameter.
The weight of silicon modifier in the melt may be within the range 0.02% to 0.08% and, preferably, the silicon modifier is strontium.
Also in accordance with the invention there is provided a method of producing the squeeze formed article as described above wherein, during the squeeze forming operation, the melt is solidified under conditions of sustained temperature and pressure such that the growth rate R of the solid phase during solidification is from 1,000 to 2,500 .mu./s and the temperature gradient G at the solid/liquid interface, expressed in .degree.C./cm is such that the ratio G/R is from 100 to 1,000 .degree.Cs/cm.sup.2.
The method may comprise the additional step of subjecting the as-formed article to a full heat treatment process being a solution treatment including heating and holding the article at a first temperature, water quenching the article and reheating and holding the article at a second temperature which is lower than said first temperature.
The squeeze formed aluminium-silicon alloy article referred to above conveniently comprises a cylinder liner for an internal combustion engine although squeeze formed articles produced in accordance with the inve
REFERENCES:
patent: 4434014 (1984-02-01), Smith
patent: 4934442 (1990-06-01), Futamura et al.
SAE Technical Paper Series No. 840123, of J. A. Eady and D. M. Smith Comalco Research Centre, International Congress & Exposition, Detroit, Mich., Feb. 27-Mar. 2, 1984.
SAE Technical Paper Series No. 860558, of R. A. Legge, D. M. Smith and G. Henkel, Comalco Research Centre, Australia, Copyright 1986 "Society of Automotive Engineers, Inc.".
Barlow John
Evans Philip H.
Frank Nicholas H.
Wilson Hamish D.
Andrews Melvyn J.
GKN Technology Limited
Koehler Robert R.
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