Mechanical Damping Characteristics of As-Cast and Austempered Aluminium-Alloyed Ductile Irons Produced With Rotary Melting Furnace Processing

The damping properties of as-cast and austempered Al-alloyed ductile iron produced by rotary furnace melting process and sand casting technique were investigated. Two Al-alloyed ductile irons, which contain 2.29 wt% Al and 3.02 wt% Al, were produced and test samples were machined, followed by heat treatment process. The samples were subjected to both conventional single step and two-step austempering processes. The microstructure of the Al-alloyed ductile irons, after chemically analysed, was characterized using scanning electron microscopy, while the storage modulus, loss modulus and damping capacity were evaluated using a dynamic mechanical analyser of model DMA 242E (Artemis) with NETZSCH format, using three-point bending mode procedure in accordance with ASTM E756-05. It was found that the ausferrite structure of the Al-alloyed ductile iron exhibited improved damping capacity than the pearlite-based Al-alloyed ductile iron of the same composition. Also, the two-step austempered Al-alloyed ductile iron yielded more improved damping capacity values of 0.23194 (1 Hz) and 0.23351 (5 Hz), respectively, at room temperature than the as-cast ductile irons investigated in this study. Graphic Abstract: [Figure not available: see fulltext.]