Synthesis of titanium silicide by mechanical alloying and pressure sintering: T.Ogitsu, K.Isonishi. (Shiga University, Ohtsu, Japan.) J. Jpn Soc. Powder Powder Metall., vol 45, no 10, 1998, 1000–1006. (In Japanese.)

Abstract

The mechanical deformation of granular bainite in a normalized high strength, low alloy steel (18CD4 steel, of composition 0.2-wt.%C-0.8wt.%Mn-1wt.%Cr-0.25wt.%Mo-0.3wt.%Si) was evaluated by comparing with the dual-phase microstructures containing, 100, 65 and 45 vol.% martensite particles obtained from this steel via an intermediate quenching treatment and with the ferrite-pearlite microstructures obtained by normalizing XC38 steel (containing 0.38wt.%C-0.8wt.%Mn-0.3wr.%Si) at three constant strain rates, 4.8 × 10−2, 4.0 × 10−3 and 4.8 × 10−4s−1. The strength and ductility parameters of granular bainite were found to be comparable with those produced from the normalized XC38 steel but had no Lüders strain which is common in the XC38 steel. Also, the microstructure with about 40 vol.% bainite granules exhibited a sensitivity to the variation in strain rate similar to that shown by the 65 vol.% martensite dual-phase structure. The mechanical properties of dual-phase granular bainite and ferrite-pearlite microstructures after tempering in the range 200–600°C, were interpreted on the basis of the changes in the microstructures. The toughness of the present steels was also studied, using circumferentially notch-cracked tensile specimens. The fracture surfaces were examined by scanning electron microscopy.