Not sure if I understand what you are looking for. EN or ASTM material equivalents? I'm asking because AMS5659 is a standard, not a specific material.

EN / ASTM or BS equivalents where a none specific material is listed.

robster,

Can you clarify why you need alternatives?  Most of these are high strength steels for aerospace or automotive racing applications, and therefore don't necessarily have alternatives because the requirements dictate aerospace quality, etc.   

I will echo TVP's comments.  These are specs for both alloys and specific properties.  While other specs call out the same general chemistry it may not be capable of the same strength and/or toughness.

AMS5659          re-melted for improved toughness and fatigue
Toughmet 3AT AMS 4596  special HT for high strength
AMS 5669 13-8ph    This is wrong, 5669 is a nickle based alloy spec
AMS4340         This is either an Al extrusion spec or an attempt at specing an alloy steel
AMS5659 15-5ph   This is the first one on the list
AMS4640         this spec is for Al bronze, there are brasses, bronzes, and alloy steels all with a generic name of 4640
AMS5630 AISI 440C   

Each case will depend on what product form of each alloy you need, does it need the same properties as the original, and how much of it you are looking for.
In many cases buying the AMS spec material will put you way ahead.

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