EVALUATION OF METHODS TO PRODUCE TOUGH CR3SI BASED COMPOSITES

Several methods of improving the toughness of Cr-Cr3Si composites prod uced by powder metallurgy have been examined. Mechanical alloying of C r-3.92 w/o with 0.5 w/o V showed the best improvement in toughness of this phase. Replacing Cr3Si with a (Cr-0.57, Mo-0.43)(3)Si, produced i n situ from a mechanically alloyed powder, offered a slight improvemen t in toughness. By combining these phases a composite was produced wit h a toughness greater than 10 MPa m(-2). Other second phase materials were also examined for providing second phase toughening of Cr3Si. The se include an Fe-Al alloy, Ni3Al + B, and 304L stainless steel. At the level of 25 v/o these materials at present do not appear to offer muc h improvement in toughness. Cr-Cr,Si composites were hot forged to pro duce a more layered microstructure and refine the microstructure of ar e-melted samples. The layered microstructure should be tougher, but ha s not been tested yet. (C) 1997 Elsevier Science S.A.