Comparison of austempering transformation in spheroidal graphite and compacted graphite cast irons

AbstractMicrostructure observations and measurements of retained austenite content are reported as a function of austempering time at temperatures of 440, 370, and 300°C after austenitising at 900°C. The results of the experimental investigation indicate that at early stages of austempering (less than ∼8 min), compacted graphite irons usually show higher amounts of retained austenite than spheroidal graphite irons. Compacted graphite irons are characterised by larger iron/graphite interface areas. After the early stages of austempering, the rate of retained austenite increase is higher for spheroidal graphite irons.