The Influence of Small Amounts of Aluminium on the Effectiveness of Cast Iron Spheroidization with Magnesium

Abstract

The influence of aluminium added in amounts of about 1.6%, 2.1%, or 2.8% on the effectiveness of cast iron spheroidization with magnesium was determined. The cast iron was melted and treated with FeSiMg7 master alloy under industrial conditions. The metallographic examinations were performed for the separately cast rods of 20 mm diameter. They included the assessment of the shape of graphite precipitates and of the matrix structure. The results allowed to state that the despheroidizing influence of aluminium (introduced in the above mentioned quantities) is the stronger, the higher is the aluminium content in the alloy. The results of examinations carried out by means of a computer image analyser enabled the quantitative assessment of the considered aluminium addition influence. It was found that the despheroidizing influence of aluminium (up to about 2.8%) yields the crystallization of either the deformed nodular graphite precipitates or vermicular graphite precipitates. None of the examined specimens, however, contained the flake graphite precipitates. The results of examinations confirmed the already known opinion that aluminium widens the range of ferrite crystallization.

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

“…Degenerations can possibly be explained by an influence of aluminum on the orientation of the graphite surface. In contrast to the literature, a decreased nodule count was measured for aluminum-alloyed material A2 [18][19][20]. Graphite nodules were also unevenly distributed, causing the formation of graphite clusters which acted as crack-initiating defects and finally reduced fatigue strength.…”

“…They reduce the solubility of carbon in the melt, which can be expressed by a higher particle number with a simultaneously smaller sphere size, since the possibility of graphite formation increases [18]. This higher formation rate promotes the formation of chunky graphite [19] and decreases nodularity [20]. If these influences and their interactions are thoroughly understood, there could be a potential to specifically adjust the fatigue strength of this alloy group by adding small amounts of aluminum.…”

Modification of Silicon Microsegregation in Solid-Solution-Strengthened Ductile Iron by Alloying with Aluminum

“…As a result, an elongation of 14%, that is required in the standard for a GJS-500-14 in this wall thickness, is not met. Due to the negative effect on the graphite morphology in ductile cast iron that is known from the literature, [23][24][25] alloying with aluminum is attributed to an increased tendency to form compacted graphite. The negative effect of alloying with aluminum on the graphite morphology is particularly evident in a significant reduction in nodularity.…”

“…4,5 In their studies, particularly, materials with minimum values of ultimate tensile strength of 520 MPa and elongation at fracture of 14% were successfully adjusted. In 2012, the solid-solution-strengthened grades This paper is an invited submission to IJMC selected from presentations at the 6th Keith Millis on Ductile Iron held October [23][24][25][26]2018 at the Sonesta Resort, Hilton Head Island, SC. It is published in the IJMC by permission of the DIS (Ductile Iron Society).…”

Investigations of Ferritic Nodular Cast Iron Containing About 5-6% Aluminium

“…As a continuation of previous investigations centred on the spheroidization of cast iron containing small amounts of aluminium [10][11][12][13][14][15][16][17][18][19][20], it was recognised as advisable to determine if it is possible to produce cast iron containing about 5-6% aluminium and compact graphite precipitates (nodular or vermicular), which would exhibit ferritic matrix in the as-cast state. It was expected that such material should exhibit even greater fire resistance than the low-aluminium silicon cast iron with compact graphite containing about 3% aluminium [5].…”