Steel composites for application as protective plates were produced via diffusion bonding. Cold work tool steels were combined with a precipitation hardening steel or a maraging steel using a deformation dilatometer and a vacuum furnace at 1150 °C for 8 h in total. Subsequently, a heat treatment was applied to achieve the final mechanical properties. The microstructure of the interface was investigated by optical microscopy, scanning electron microscopy, electron backscatter diffraction, energy dispersive X-ray spectroscopy and hardness measurements. The results are compared with a simulation of the diffusion of elements performed by MatCalc. Both composites achieve high hardness near the surface of the cold work tool steels, which can have a positive effect on the destruction of projectiles on impact. The influence of carbon diffusion can be observed up to a depth of 3 mm from the interface. As a result of carbon diffusion, soft zones are formed on both sides of the interface, which can be attributed to decarburization, phase transformation and carbide formation. The tough back layer is designed to absorb the remaining energy of the projectile. The combination of a hard front layer and a tough rear layer provides an optimal combination of materials against ballistic threats.

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The effects of post-processing heat treatments on hot-rolled Ti–6Al–4V with extra low interstitial concentration were investigated. The 2 mm sheets were rolled in the single β phase field region and subsequently cooled in air. A continuous cooling transformation (CCT) diagram was generated, revealing the strong influence of the cooling rate on both microstructure and hardness. Cooling rates between 0.01 and 200°C s−1 were selected. While rapid cooling resulted in a martensitic transformation β → α′, a decrease in the cooling rate led to a progressive spheroidization of the lamellar (α + β) microstructure. With a focus on the established CCT continuous cooling transformation diagram, this study contains insight on the microstructure evolution of the Ti–6Al–4V ELI alloy during cooling from the single β phase field region.