AMS 5662 and AMS 5663 – Does Size Matter?

Broder Metals Group stock Alloy 718 to meet AMS standards 5662 (solution annealed condition) and 5663 (solution annealed and aged condition) in sizes from 1” (25.4 mm) to 7” (177.8 mm) (and up to 305 mm (12”) for API material).  One question is what difference one should expect in properties in such a large size range.  This article will detail those differences.

The latest AMS (Aerospace Material Specification) standards applicable to 5662 and 5663 are both revision N.  Both cover bar, forgings, flash welded rings for up to 254 mm (10”) in diameter or 503 cm² cross-sectional area and stock of any size for forging or flash welded rings.

Alloy 718 to AMS 5662 and 5663 are used typically (but not only) for parts requiring high resistance to creep and stress-rupture (up to 704°C) and oxidation resistance up to 982°C.  If you are interested in the difference between API and AMS material, please see relevant articles in our technical series.

As one would probably expect, the chemistry between small and large diameters does not differ, nor does the melting practice (multiple melted using consumable electrode practice in the remelt cycle or induction melted under vacuum).    The first difference that will be noted is in the solution treatment heat treatment cycle for both materials where thicker material may be held for different times than smaller sizes at temperature (within +/- 14°C solution annealing temperature range) to account for the difference in cross-sectional thickness. The ageing cycle of AMS5663 does not have that leeway and all sizes are treated at the same ageing times and temperatures.

The next difference comes in the expected grain size.  Both material standards allow bars and flash welded rings under 58 cm² cross sectional area to have a grain size of ASTM 5 or finer.  From 58 to 503 cm² cross sectional area the grain size is allowed to be ASTM 4 or finer.

However, most differences come with the mechanical properties expected.  Please note that although material up to 254 mm diameter can be tested in the longitudinal direction, only material larger than roughly 70 mm / 3” dia can be tested in the longitudinal direction.  For more information on longitudinal versus transverse direction testing, please see the relevant article in our technical series.

The relevant (minimum) tensile requirements at different sizes and direction of test are as follows (AMS5662 properties are after the sample has been subject to the ageing cycle of 5663):

Finally, stress Rupture properties at 649°C are the same as far as time to rupture is concerned for all sizes (not less than 23 hours at a minimum axial stress of 689 MPa) but there is a further requirement for the elongation at rupture to be not less than 4% in 4D for product of less than 127 mm / 5” diameter.

We would be pleased to answer any questions or provide quotes for our range of small and large dia bars on request. Please telephone the main Broder Metals Group sales team on +44 (0) 114 232 9241 or email sales@broder-metals-group.com or for specific quotes on our range of Aerospace (AMS) grades please contact our Broder Aerospace sales team on +44 (0)114 349 3595 or email sales@broder-aerospace.com.