Effect of Reduction Rate on Microstructure and Properties of Al-Si Coating on Hot Formed Steel

Tailor rolling blanks is widely used in automobile parts.The effect of rolling with different reduction rate on the microstructure and properties of Al-Si coating on hot formed steel was studied.The results show that the structure and morphology of hot formed steel with Al-Si coating remain unchanged after rolling, and the structural characteristics of aluminum matrix, alloy diffusion layer and boron steel matrix remain from outside to inside.With the increase of reduction rate, the coating thickness of the test steel decreases, but the alloy diffusion layer thickness remains unchanged.When the reduction rate is 10%-30%, the continuity of Al-Si coating and alloy diffusion layer is not damaged, but cracks appear in the alloy diffusion layer, and the crack density increases with the increase of reduction rate.The total thickness reduction rate of the coating is slightly higher than the reduction rate.When the reduction is 40%, the coating thinning phenomenon is more obvious, and part of the aluminum substrate is in direct contact with the boron steel substrate.The tensile strength, yield strength and matrix hardness of the tested steel increase with the increase of reduction rate, while the elongation decreases sharply, but the elongation at break is ≥2%.