Appeal No. 1996-1573
Application No. 08/186,160
1. A superplastic aluminum alloy comprising from 4 to 15% by weight of
Mg, from 0.1 to 1.0% by weight of one or more elements selected from the
group consisting of misch metal, Zr, V, W, Ti, Nb, Ca, Co, Mo and Ta, and
the balance being Al and unavoidable impurities, wherein the alloy (i)
contains 0.1 to 4.0% by volume of dispersed spheroidal precipitates of
intermetallic compounds having a particle size of 10 to 200nm, and (ii) has a
grain structure wherein the mean grain size is from 0.1 to 10 µm, and from
10 to 50% of the grain boundaries have a misorientation of less than 15°.
The examiner relies upon the following references as evidence of obviousness:
Watts et al. (Watts) 3,876,474 Apr. 08, 1975
2
Watanabe et al. (Watanabe) 4,654,543 Feb. 24, 1987
Sawtell et al. (Sawtell) 4,689,090 Aug. 25, 1987
3
Watanabe et al. (British '694) 3GB 2 135 694 Sep. 05, 1984
Hales, S.J. et al. (Hales), "Grain Refinement and Superplasticity in a Lithium
Containing Al-Mg Alloy by Thermomechanical Processing", Journal de
Physique, vol. 48, no. 9, pp. C3 285-C3 291. (Sep.1987)
Appellants' claimed invention is directed to a superplastic aluminum alloy
comprising from 4 to 15% by weight of Mg, from 0.1 to 1.0% by weight of one of the recited
elements, and aluminum. The alloy has the specified grain structure and grain boundaries,
and also contains dispersed spheroidal precipitates of intermetallic compounds having the
recited particle size.
2 U.S. equivalent of and used interchangeably with GB 2 135 694 by the examiner in the
examiner's answer.
3 British equivalent of and used interchangeably with U.S. 4,654,543 by examiner in the
examiner's answer.
2
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