Magnesium parts with muscle

Automotive designers are specifying die-cast magnesium parts in applications once dominated by aluminum, zinc, and other structural materials. Production and New Program Manager, Magnesium and Intermediate Zinc Castings FisherCast Global Corp. Peterborough, Ont. Magnesium alloys increasingly replace aluminum, zinc, and other materials in structural automotive parts because they are much lighter. Magnesium's low density significantly reduces weight by volume compared to aluminum and zinc. Magnesium is 33% lighter than aluminum and just about a quarter the weight of zinc. Yet magnesium has the highest strength-to-weight ratio of all structural metals, except for titanium. Its density is only slightly above that of plastic, but its high (72 W/m-K) thermal conductivity lets it dissipate heat more effectively. This makes magnesium a better candidate for parts that see elevated temperatures where creep is a concern. Additionally, magnesium damps out vibration and noise, resists impacts and dents, and is fully recyclable. High-pressure, hot-chamber die-cast AZ-91D magnesium, for example, now takes the place of aluminum in small components for steering columns, valve covers and housings, shift actuators, and intake-manifold blades. Magnesium die-cast components also go into small engines, power tools, and electronic and medical devices. Low density gives magnesium the best economics/volume compared to aluminum components of equal geometry. Some plastics are slightly lighter than magnesium and competitive in price/volume. But the physical and mechanical properties of magnesium often let it outperform plastic where certain strength, stiffness, heat dissipation, dampening, EMI shielding or recyclability are important. Weight reduction is a strong motivator in many applications, but magnesium's net-shape castability in the hot-chamber die-casting process is often the reason for using it. Designers should evaluate the total cost of a small die-cast component, rather than just looking at price/pound. Net-shape castings eliminate secondary machining and can significantly reduce processing time and waste material. The alloy has excellent