Production and Mechanical Characterization of Steel/Al-B4C Layered Circular Hybrid Composite Materials

Abstract

This study aimed to develop a layered circular metal composite that would combine high strength, low density, and developable surface properties. The outer part of this composite material called the sheath was made of AISI 4140 steel, and the inner part, as the core, was composed of Al/B4C (boron carbide) mixed metal matrix composite. Al/B4C powder mixing ratios were determined by volume rate as 5, 15, and 25% B4C. Al2024 powder with an average particle size of 40 µm and B4C with particle sizes of 5, 17, and 58 µm were used. Composite materials were produced by forming the pre-products obtained by compressing Al/B4C powder mixtures into steel tubes using the drawing method. The drawing process was carried out at room temperature, 250 °C, and 400 °C, and with three different deformation extents (16, 30, and 37%). In the composite materials produced under all temperature conditions, increasing of the deformation extent increased the compression strength of the materials. Compression strength also increased with B4C reinforcement at all temperature conditions, but it decreased when the ratio of reinforcement passed over 15%. The gas nitriding process was applied to the produced composites to improve their surface properties. Strength values showed improvement after the nitriding process, and a thicker nitride layer was obtained on the steel sheath in highly deformed materials. As a result, the study presented the production of a composite with different sheath-core materials by rod drawing method and the effect of production variables on the material's mechanical properties. In addition, it was shown that the desired surface quality can be obtained by the gas nitriding process at low temperatures.