Effects of Mn and Al Contents on Microstructure and Mechanical Properties of TiB2/Fe-15Cr-Mn-Al Composites

Two kinds of TiB2/Fe-15Cr-Mn-Al composites with low Mn and low Al as well as intermediate Mn and intermediate Al were prepared by using mechanical alloying (MA) with subsequent spark plasma sintering (SPS). The effects of Mn and Al contents on the microstructure as well as mechanical properties of the composites were investigated and compared with the composite with high Mn (20 wt.%) and high Al (8 wt.%) studied previously. The results indicated that during the sintering process, CrFeB-type boride formed in the two different composites which was similar to the high Mn and high Al composites but no Mn2B-type boride was observed. Furthermore, the matrix structure changed with the content of Mn and Al. Low contents of Mn (2 wt.%) and Al (1.5 wt.%) led to solid solution-strengthened α-Fe (Cr, Mn, Al) matrix, whereas intermediate contents of Mn (10 wt.%) and Al (5 wt.%) resulted in Fe2AlCr intermetallic matrix. The two composites showed high compressive strength and Vickers hardness, which increased as the Mn and Al contents in the matrix increased, which mainly resulted from the difference in hardness between α-Fe (Cr, Mn, Al), Fe2AlCr and CrFeB.