Development of Dual Phase ADI

A.BASSO; R. MARTINEZ; J. SIKORA

Beijing - China

Simposio; Eighth International Symposium on Science and Processing of Cast Iron; 2006

Tsinghua University

The present work describes the studies on two types of heat treatment cycles leading to obtain mixed microstructures referred to as “dual phase ADI”, consisting in a mixture of ausferríte and allotriomorphic ferrite. A conventional ductile iron melt, alloyed with Cu and Ni was employed. Once the intercritical interval (equilibrium zone among ferrite, austenite and graphite) was correctly identified through the precise determination of the lower and upper critical temperatures, different heat treatment cycles were performed. The adequate handling of the heat treatment variables allowed the control of the amounts, morphology and distribution of the micro constituents. One type of thermal cycle allowed to attain microstructures composed of different amounts of ausferrite and dispersed allotriomorphic ferrite. The other type of thermal cycle allowed the formation of microstructures consisting in ausferrític matrices containing continuous and well defined networks of allotriomorphic ferrite, located at the grain boundaries of the recrystallized austenite. Mechanical test performed on samples with mixed structures showed interesting combinations of strength and ductility