Influence of Aluminum on Fatigue Strength of Solution-Strengthened Nodular Cast Iron

Abstract

The fatigue strength of high silicon-alloyed nodular cast iron is influenced by casting defects and graphite precipitates. The literature as well as the findings of this work show that these microstructural constituents can be tailored by controlling silicon microsegregation. In addition, segregations also affect the ferritic matrix microstructure locally. In the present work, silicon segregations in high silicon-alloyed ductile iron are specifically manipulated by small additions of aluminum. It was demonstrated how the aluminum content affects a wide range of microstructural constituents across a variety of length scales. Specimens from alloys with small additions of aluminum were fabricated and tested by rotating bending. Results show that the fatigue strength can be increased compared to a reference alloy with no aluminum. Microstructure analysis as well as fractography were performed concluding that microstructural changes could be attributed to the increased aluminum content, which allows the fatigue properties to be tailored deliberately. However, according to the results of this study, the negative effect of aluminum on castability and graphite morphology limits the maximum content to approximately 0.2 wt.%.

Plasticity Resource of Cast Iron at Deforming Broaching

“…At the same time, crack initiation was found in the stress range of 280-330 MPa. Gebhardt and colleagues studied the behavior of high-alloy nodular cast iron during its deformation [36]. The authors proved that the aluminum content affects the mechanical characteristics of this cast iron type.…”

“…This provides significant plastic deformation in the surface layer of the machined workpiece. For example, after 35-40 machining cycles of plastic materials (35)(36)(37)(38)(39)(40) drawing cycles using the deforming elements with tightening), the deformation in the workpiece subsurface layers can reach a value of 350-400% [1].…”

Potential of inverted process-chain development to improve crash box performance

“…Similar approaches of fully integrated design workflows can be found in the field of aminated continuous fiber-reinforced composites [39]. In this context, local property grading for nodular cast iron has been studied by Gebhardt et al [40] and Ripplinger et al [41]. Both works showed a benefit in terms of increased fatigue strength in the case of high silicone-alloyed nodular cast iron and ferrite graded nodular cast iron.…”

The effect of silicon microsegregation on the mechanical properties of high silicon alloyed ductile cast iron under monotonous loading

“…Promising approaches exist to manipulate the segregation profile, as indicated by Franzen et al [ 9 ], and thereby tailoring the mechanical properties of Si-DCI. However, only little in-depth experimental studies of the influence of the Si-segregation profile on the mechanical properties of Si-DCI were published in the literature [ 14 ]. This is probably related to the strong heterogeneity of the microstructure which leads to the interplay of multiple factors that influence the mechanical properties [ 15 , 16 ].…”