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SandCast Alloys

The grain sizes of sand cast alloys are typically of 200µm. The fraction of retained intermetallics in T6 samples of the ZA84, ZA85, ZA105 and ZA107 alloys increased with alloying content. The primary intermetallic particles reatined in the T6 samples of the sand cast alloys were found to be equilibrium ƥ phase. Fig.3(a). The peak-aged microstructures had a relatively fine-scale distribution of icosahedral precipitates. The distribution of such porecipitate varied from grain to grain for each alloy. Fig.3(b). Examinations of peak aged microstructures of all four alloys did not detect any particles or precipitates of Mg12Al12 phase.

(K.U. Kainer, Magnesium: Proceedings of the 7th International Conference,p.28)

Electrostatic fluid bed

As the name  implies, this process combines elements of both fluidized-bed and the electrostatic-spray processes. Standart fluidized-bed equipment is used, but in addition, the plastic particles are given a negative charge by applying in a high voltage( approximately 90000volts) direct current. The part to be coated is electrically grounded and suspenden above teh fluidized bed, so that the charged particles can be attracted to the part. The process has several advantages over the straight fluidized-bed porcess, among which are:
- The part to be coated does not need to be immersed.
- Preheating the part is not necessary for particle adhesion.
- Large fluidized beds are not needed to coat large parts.
- The processes can be used to coat thin, low- mass parts such as wires that cannot be coated by the straight fluidized-bed process due to their poor heat retention.
The porcess has benn found most useful in coating large complex parts and thin-gauge wire.

(James J. Licari, Coating Materials for Electric Applications, p.239)

Hot molding

Hot molding is a term coined by Textron to describe a low-pressure hot pressing porcess that is designed to fabricate shaped SiC-aluminum parts at signifanctly lower cost than the typically diffusion bonding, solid-state process. The SCS-2 fibers can withstand molten aluminum for long periods; therefore, the molding temprature can now be  raised into the liquid –plus-solid region of the alloy to ensure aluminum flow and consolidation at low pressure, thereby negating teh requirement for high-pressure die molding equipment.

The best way of describing hot molding process is to draw an anology to the autoclave molding of graphite epoxy where components are molded in an open-faced tool. The mold in this case is a self-heated, slipcast ceramic toll embodying the profile of the finished part.  A plasma sprayed aluminum preform  is laid into teh mold, heated to a near molten aluminum temperature, and pressure consolidated in an autoclave by a “metallic” vaccum bag. The mold can be profiled as required to produce near net shape parts including tapered thicknesses and section geometry variations.

(J.Füller, Developmenst in the Science and Technology of Composite Materials, p. 331-332)

Damage anisotropy

The damage anisotrphy is easily observed in metal specimens subjected to creep under nonproportionalloading conditions. Microstructural observations under nonproportional loading conditions. Microstructural observations by Trapczynski, Hayhurst, and Leckie(1981) allowed the identification of two classes of metallic materials: copper-like, where cavitation takes place on grain boundaries essentially perpendicular to the maximum principa stress,and aluminum alloy-like, where grain boundary cavitation is much more isotropically distributed. The complexity of the damage accumulation depends on the loading path or on the rotation of principals stress axes with respect to material fibers.

(Jacek Skrzypek, Artur Ganczarski, Modeling of Material Damage and Failure of Structures, p. 70)