The Current Status of the Metallurgy and Processing of Austempered Ductile Iron (ADI)

Abstract

In the last three decades, the revolutionary material; the austempered ductile iron (ADI) with its unique combination of mechanical properties, has been offering the design engineer alternatives to conventional material process combinations, This review is an attempt to compile the results of the worldwide explosion of research and development that followed the announcement of the first production of this material, meanwhile, reference is made to the work that has been carried out at CMRDI over the past decade. This paper is not designed to provide an in-depth investigation of any specific technology, but is rather a macro-analysis of the current state of metallurgy and processing of ADI. Better understanding of the strengthening mechanisms of ADI led to the development of new techniques such as ausforming, squeeze casting as well as two-step austempering, which contributed to enhanced strength of the alloy. Abrasion resistance could be markedly increased through the development of carbidic ADI (CADI), bainitic/Martinsitic (B/M) ADI, locally austempered ductile iron using induction hardening techniques, as well as laser surface hardening. Machinability problems of ADI, which have limited its mass production for long, have been solved through the development of new machinable types of ADI as IADI with mixed ferrite/ausferrite structures. Production of thin wall ADI components may offer potentials for applications, and this could be achieved through casting or cold rolling, where strain hardening phenomena seems to be of special interest. Thin wall ADI castings are capable to build complex thin wall parts of high strength.