Microstructure and mechanical behavior of spark plasma sintered TiB2/Fe-15Cr-8Al-20Mn composites

Abstract

Fe-15Cr-8Al-20Mn matrix composites with varying volume fractions of TiB2 (15–30 vol%) were fabricated by the combination of mechanical alloying (MA) and spark plasma sintering (SPS). The influence of TiB2 particulate content on the microstructure and mechanical properties of the composites was investigated in detail. Mechanical alloying between metallic elements was almost completed after approximately 30 h of milling, and the final ball milled powders consisted of a supersaturated α-Fe(Cr, Mn, Al) metallic solid solution and TiB2 ceramic component. Following the sintering process, the sintered composites were composed of Fe2AlCr, CrFeB-type boride, Mn2B-type boride and TiB2. The compressive strength and Vickers hardness of the sintered composites were related to the volume fraction of TiB2 in the matrix, which are all much higher than those of the reported TiB2/Fe-Cr composites with the same volume fraction of TiB2. The highest Vickers hardness and compressive strength at room temperature are 767 ± 18 HV and 2835 ± 21 MPa, respectively. These composites still show relatively high compressive strength as the testing temperature increasing up to 600 °C. The high Vickers hardness and compressive strength were mainly attributed to the precipitation strengthening of CrFeB, Mn2B and Fe2AlCr and nanocrystalline microstructure produced by the combine of MA and SPS.