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A pilot production program was initiated to evaluate the suitability of recycled AZ91D magnesium alloy ingot in a production steering column component. Class I A291D magnesium alloy scrap was remelted and refined using an argon flotation technique. The non-metallic inclusion content of the metal was continually monitored by a newly developed light reflectance technique. In addition, chemistry was checked and adjusted to bring the metal into ASTM chemistry specifications. Analysis of the refining operation with respect to cleanliness showed that modifications to the argon gas distribution were necessary. After the necessary modifications were implemented, metal refining efficiency increased. The refined alloy was cast into 11 kg (25 lb.) ingots that were subsequently remelted at Contech's production facility. Parts were produced under the same conditions used for “virgin” metal, and the metal quality was again assessed with the light reflectance technique.

Semi-solid processing (SSM) has many advantages in that the alloy is cast at lower temperatures (i.e., in the two-phase region) giving rise to reduced die wear, as well as giving rise to novel microstructures. The resultant SSM processed castings are dendrite-free and do not contain hot tears; rather, the SSM structure is globular, and the liquid phase surrounding the globules acts as a “lubricant” during processing. Moreover, the flow of the slurry into the die cavity is more laminar than turbulent, since the starting metal is in the mushy region. This concept of SSM processing was realized by the development of a continuous process titled: CRP - Continuous Rheo-conversion Process. In this process, one allows the incipient solidification of alloy melt(s) under the combined effects of forced convection and rapid cooling rates. In the CRP, two liquids held at particular level of superheat, are passively mixed within a reactor.

The emergence of squeeze casting process for aluminum alloys has given material and design engineers a new alternative to conventional casting techniques: gravity permanent mold (GPM) and conventional (high velocity, high pressure) die casting. In recent years, the squeeze casting process has been applied to near net shape products requiring high impact strength, high fatigue strength, pressure tightness, or high wear resistance. This paper provides both a description of the HVSC squeeze casting process and examples of select components manufactured at CONTECH. In this study, the mechanical (tensile, impact, fracture toughness, fatigue strength) and wear properties of various aluminum alloy squeeze castings are also compared with those of gravity permanent mold and conventional die-castings. Results indicate that mechanical and wear properties of aluminum squeeze castings are superior to those of gravity permanent mold and conventional die-castings.