EFFECTS OF NI ADDITION ON MECHANICAL-PROPERTIES OF TIB2 SIC COMPOSITES PREPARED BY REACTIVE HOT-PRESSING (RHP)/

Effects of Ni addition on the mechanical properties of TiB2/SiC compos ites produced by RHP according to the chemical reaction Si + 2TiH(2) B4C --> 2TiB(2) + SiC + 2H(2) up arrow have been investigated. The fr acture strength and Vickers hardness reach their highest values at 2 w t % Ni content, but the fracture toughness reaches its lowest value at this Ni content. Suitable Ni content can enhance the boundary strengt h of the composites and it is supported by SEM observation and residua l stress measurement by XRD technique. On the other hand, the results of the residual stress measurement show that the residual machining st resses in the surface layer of the specimens are not constant but chan ge with different directions.