PSI - Issue 3

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Vittorio Di Cocco et al. / Procedia Structural Integrity 3 (2017) 224–230 Author name / Structural Integrity Procedia 00 (2017) 000–000

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a)

b) Fig. 8. Quantitative phases damage: a) Zn-Sn coatings, b) Zn-Ti coatings.

4. Conclusions In this work a comparison between coatings obtained from a Zn-Sn and a Zn-Ti bath has been investigated both in terms of intermetallic phases, bending behaviour and phases damages. Concerning intermetallic phases, the 3%Sn bath generates the traditional intermetallic phase that can be obtained using pure Zn or Zn-Pb baths. High values of Sn allows to obtain a quasi-linear kinetics of coating formation for all investigated dipping times. Zn-Ti bath allows to generate coatings characterized by the presence of  and a multiphase layer which represent the main layer of coatings. This multilayer is composed of lamellar phases and a compact phase in a ductile matrix. Furthermore, the presence of Ti in the bat allows to obtain higher values of coating thickness The bending test shows higher values of bending strength in Zn-Sn than Zn-Ti coatings, despite the thicknesses of Zn-Ti coatings are greater than Zn-Sn coatings. The damage morphologies are characterized both by the presence of longitudinal and radial cracks. Only the radial crack damage is quantified using a damage parameter defined as the number of radial cracks for millimeter of deformed arc. Results of quantification show higher values of damage in the  phase and the presence of damage in  phase due to cracks which come from  phase (only for Zn-Sn coatings). No damage has been observed in η phases (Zn-Sn coatings) and in the multiphase layer (Zn-Ti coating). References De Abreu Y., Da Silva A., Ruiz A., Réquiz R., Angulo N., Alanis R., Study of zinc coatings on steel substrate attained by two different techniques, Surface and Coatings Technology, 120-121, 682-686, 1999. Duncan J.L., Ding S.-C., Jiang W.L., Moment-curvature measurement in thin sheet-part I: equipment, International Journal of Mechanical Sciences 41, 249-260, 1999. Duncan J.L., Ding S.-C., Jiang W.L., Moment-curvature measurement in thin sheet-part II: yielding and kinking in aged steel sheet, International Journal of Mechanical Sciences 41, 261-267, 1999. Kim S.-R., Nairn J.A., Fracture mechanics analysis of coating/substrate systems. Part I: Analysis of tensile and bending exeriments, Engineering Fracture Mechanics, 65, 573-593, 2000. Kim S.-R., Nairn J.A., Fracture mechanics analysis of coating/substrate systems. Part II: Experiments in bending, Engineering Fracture Mechanics, 65, 595-607, 2000. Marder A.R., The metallurgy of zinc-coated steel, Progress in Materials Science, 45, 191-271, 2000. Natali S., Di Cocco V., Iacoviello F., Prove di flessione non tradizionali su acciai zincati: caratterizzazione cinematica e statica del meccanismo ed identificazione dello stato di danneggiamento dei rivestimenti, La Metallurgia Italiana, 2004. Reumont G., Voct J.B., Iost A., Foct J., The effects of an Fe-Zn intermetallic-containing coating on the stress corrosion cracking behaviour of a hot-dip galvanised steel, Surface and coatings technology 139, 265-271, 2001. Tzimas Evangelos, Papadimitrou G., Cracking mechanisms in high temperature hot-dip galvanised coatings, Surface and Coatings Technology, 145 176-185, 2001.