Mercalloy HD - Suitable for critical parts that require exceptional ductility and high-cycle fatigue life.

The Mercalloy series offers an attractive solution for higher performance structural diecastings.

Mercally HD (high ductility, AA 368) is a 9% Si alloy optimized for a great mix of castability and properties (especially elongation).

Castability: Because of the absence of the iron phase beta-needles, the 368 (like all Mercalloy alloys) have excellent fluidity and resistance to hot cracking, which makes it possible to produce castings that are large in size and intricate in shape. Because of its lower silicon content, the fluidity of 367 and 368 is somewhat lower than that of 362 at the same temperature. Alloys 367 and 368 can have the same fluidity as 362 with slightly higher casting temperature, and the feeding characteristics are improved over any comparable structural diecasting alloys.

Crash behaviour: The big advantage in crash relevant applications that any Mercalloy has over other structural diecasting alloys is its low manganese content of 0.25-0.35% which accounts for its greater ability to absorb energy on impact at high strain rates (due to reduced intermetallics Mn-compound, Al12Mn3Si2 ). This low manganese range also increases its tolerance of a higher iron level of 0.25% max Fe (compared to similar alloys) in avoiding the precipitation of the intermetallics Mn-compound.

Finishing: Polished finishes of the 368 alloy are good. Anodized coatings are good because of the small size of the die cast eutectic silicon. Very good finishes are achieved with electroplated and chemical conversion coatings.

Corrosion Resistance: Cast parts in Mercalloy 368 can be used without corrosion protection. This alloy has excellent resistance to corrosion and stress corrosion cracking [higher than 360 and A360] because of the low copper content.

Machinability: MercAlloy 367 and 368 have very good machinability when wear resistant tools with liberal rakes and clearance angles are used at moderate to fast speeds.

Weldability: Excellent welds are obtained by common methods, if entrapped air from die casting is not a problem. Brazing is not recommended.

Mechanical Properties

Typical Mechanical Properties at 0.20% Mg*
Casting Process and Temper Aging Time and Temperature Tension Endurance Limit ksi (MPa)
Ultimate Strength ksi (MPa) Yield Strength ksi (MPa) Elongation (%)
Die Cast 368.0--F as cast 38-40  (260-275) 18-20  (125-140) 10-12 21  (145)
Die Cast 368.0--T6 6 hr at 320 F 41-43  (280-295) 27-29  (185-200) 14-16 20  (140)

* These properties are for separately cast tensile specimens


Alloy 368.0–Chemical Composition Limits
Si Fe Cu Mn Mg Cr Ni Zn Ti Sr Other Elements
Each Total
8.5-9.5 0.25 0.25 0.25-0.35 0.10-0.30 -- -- 0.10 0.20 0.05-0.07 0.05 0.15


All Mercury Marine aluminum propellers are manufactured using Mercalloy 368. This material features exceptional ductility and strength, in addition to excellent corrosion resistance.

Suitable automotive applications would include suspension components, shock towers or other critical parts that require exceptional ductility and high-cycle fatigue life.

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