Illustrations from the Tesla Model 3 repair manual, which have begun circulating on social media, show that the sports sedan is built on a combination of steel and aluminum components. 

“Tesla uses three different grades of steel, from mild steel used on the outer body structure, where it’s designed to absorb initial impacts, and high-strength, to ultra-high-strength (steel) used in the vehicle’s core. For instance, the A pillar and B pillar is fabricated from ultra-high-strength steel in order to provide maximum rollover protection. Model 3’s front frame rail is a composition between high-strength and ultra-high-strength steel and serves as the main support for the front ‘crumple zone,’” writes Teslarati, a forum for Tesla enthusiasts. 

Teslarati has more here.