Speaker
Description
High Silicon Strengthened Ductile Irons (HSiSDI) with 3.5, 4.2 and 4.5 % wt. silicon contents were produced in Y-blocks with different geometries to investigate the effects of silicon and solidification rate on microstructure integrity and tensile mechanical properties. With increasing silicon the strength of the HSiSDs increased, while the ductility decreased progressively, with an abrupt reduction for silicon content higher than 4.2 % wt. With decreasing solidification rates the graphite degeneracy with the appearance of chunky graphite became more significant at the highest silicon contents, so chemical ordering and graphite degeneracy seemed to be qualitative explanations of tensile property degradation. However, a deeper analysis of the relationship between solidification rate, microstructure and tensile properties was realized through an innovative approach based on the Matrix Assessment Diagram (MAD) [1,2], where the parameters of Voce equation resulting from best-fitting the experimental tensile flow curves of a significant number of HSiSDI samples, were plotted. For 3.5 % wt. silicon content, the MAD analysis indicated that the microstructure was sound for any solidification rate, while for 4.5 % wt. the microstructure was sound only for the fastest solidification rates. For 4.2 % wt. silicon content the MAD analysis pointed out that the tensile plastic behaviour and the microstructure integrity was in between the 3.5 and 4.5 % wt. silicon contents, representing indeed a composition threshold where however the reliable microstructures were found with the fastest solidification rates, while for the slowest ones considerable variability was found. Support to MAD analysis results was given from microstructure observations.
1 - Angella G., Cova M., Bertuzzi G., Zanardi F. Int. J. of Metalcasting, 14 (3) 2020, pp 816-826.
2 - Angella G, Donnini R., Zanardi F. Int. J. Cast Metals Research 2020, Vol. 33, NOS. 2–3, pp. 89–102.
| Speaker Country | Italy |
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