Development of non-lubricated die for magnesium sheet forming of car body part

According to current development trends for automotive body parts, light weight is a key issue in improving fuel efficiency and CO2 reduction. Compared to steel and aluminum, magnesium has a relatively low specific gravity. However, it is challenging to use magnesium to produce a product at room temperature because magnesium has a Hexagonal Close-Packed (HCP) crystal structure. Therefore, the structure is not suitable for plastic deformation without using a heating system. As a result, a magnesium sheet and die need to be heated from 250 to 300°C. Unfortunately, this procedure has positive and negative effects. It increases not only the material’s elongation, but also the friction between the material and die during warm forming. Furthermore, lubricant cannot be used due to corrosion occurring on the surface of a part after manufacturing. To overcome these challenges, we developed a “Partition panel,” which is a warm-formed part with a non-lubricated die with a Diamond-Like Carbon (DLC) coating. A one-quarter sized prototype was successfully produced with the DLC-coated non-lubricated die, and its characteristics were verified through an evaluation of the friction coefficient and mechanical properties.