FREQUENTLY ASKED QUESTIONS

The size of the SiC particles varies with different material systems. For volume loadings between 15 and 25%, the average particle size is about 5 microns (µm). Highly loaded MMCs, such as 6092/SiC/40p, use slightly coarser SiC particles.

In general, DWA-USA Al MMCs can accept most surface treatments that are used for conventional aluminum. Chemical conversions such as MIL-DTL-5541 Class 1A can easily be applied without process modification. Anodizing can be performed using both chromic and sulfuric acid techniques.

Al MMCs are machined in the same fashion as conventional aluminum alloys, however, the presence of SiC particles fundamentally changes machining response and tool wear.  Polycrystalline Diamond (PCD) cutters are highly recommended for the best tool life, as is liberal use of cutting fluids.  The conventional wisdom regarding Al MMCs is that it is easier to machine than titanium and more like conventional, hard alloy aluminum.

Fusion welding techniques such as TIG and MIG are not recommended for Al MMCs, given an adverse reaction between the SiC particles and aluminum matrix in the molten weld zone that leads to gas evolution and porosity.  Friction welding using inertia or stirring are very effective ways to join MMC to itself or conventional aluminum.

Al MMCs possess excellent isotropy. For example, typical variation in mechanical properties from the L to the LT orientation is 3 to 5% based on the material system and product form.

Al MMCs with SiC volume loadings between 10 and 25% can be extruded, rolled and forged to very high degrees of net shape.  Al MMCs with higher loadings, such as 6092/SiC/40p, can be extruded into simple shapes (ex: “round-to-round”) and forged to near-net-shape.  Very highly loaded systems such as 6063/SiC/50p are used in the as-VHP condition or can be open die forged from VHP billet.

Lead-time depends on many factors.  For serial production of billets and extruded shapes, lead-time may be 16 weeks for the initial delivery point, and as frequent as every 4 weeks thereafter.  Lead-times for prototype or “one-off” requirements are quoted on a “case-by-case” basis and are influenced by the availability of inventoried stock.