Ausferritic ductile irons (adi): analysis of modern alloying schemes

A database of chemical compositions of ausferritic ductile irons (ADI) was created based on publications in reputable scientific journals (Materials and Design, Materials Science and Engineering A, Journal of Materials Engineering and Performance, Journal of Materials Research and Technology (Elsevier), Metallurgical and Materials Transactions A, International Journal of Metalcasting (Springer), Materials, Metals (MDPI), Materials Transactions JIM, ISIJ International и др.). The search was carried out for 35 years (1990–2025), with the greatest attention paid to publications for the period 2020–2025. A statistical analysis of the chemical compositions of ADI from the database was carried out, which revealed a number of patterns. The values of average concentrations, standard deviations from averages, and confidence interval boundaries for average values of chemical element concentrations were determined using the Student’s distribution at a significance level of 0.05. The limiting ranges of ADI alloying with the main elements were established: carbon from 2.78 to 3.87 %, silicon from 0.28 to 4.69 %, manganese from 0.07 to 1.01 %, copper from 0.01 to 1.4 %, nickel from 0.001 to 2.0 %, molybdenum from 0.001 to 0.5 %. Graphs of the dependencies of the distribution frequency of the studied ADI alloys on the content of carbon, manganese, copper, nickel, molybdenum and magnesium were constructed. Characteristic maxima of the distribution frequency of the alloys were found, falling on the ranges of concentrations of the following elements: carbon 3.40–3.55 % (42 % of alloys), silicon 2.03–2.91 % (90 % of alloys), manganese 0.22–0.41 % (41 % of alloys). For copper, nickel and molybdenum in ADI, statistically significant concentration maxima were not revealed. The distribution frequency of ADI alloys was analyzed depending on the concentration combinations of the following pairs of chemical elements: С–Si, Si–Mn, Cu–Ni, Mo–Ni, P–S, Mg–C. Combinations of C–Si and Si–Mn concentrations, characteristic of most alloys, were revealed and displayed on the diagrams as local, clearly defined zones. Somewhat less defined areas of stable concentration combinations were found for the pairs: Mg–C and P–S. A number of groups of stable combinations of Cu–Ni, Mo–Cu, Mo–Ni concentrations were established and displayed on the diagrams as several corresponding zones. ADI groups were revealed: molybdenum‑free, low‑copper, low‑nickel; the most widely represented group is complex‑alloyed ADI: 0.6–1.4 % Cu, 0.5–2.0 % Ni, 0.15–0.3 % Mo. Statistical analysis allowed us to identify the most frequently used ADI alloying ranges: carbon 3.50–3.59 %, silicon 2.44–2.66 %, manganese 0.29–0.38 %, copper 0.39–0.62 %, nickel 0.46–0.81 %, molybdenum 0.13–0.24 %, magnesium 0.042–0.051 %, phosphorus 0.024–0.035 %, sulfur 0.011–0.015 %. As a result of statistical processing of the entire data array, the weighted average chemical composition: 3.54 % C, 2.55 % Si, 0.33 % Mn, 0.51 % Cu, 0.64 % Ni, 0.18 % Mo, 0.046 % Mg, up to 0.03 % P, up to 1.1% S. This composition is recommended as optimal. An analysis and comparison of chemical compositions of a number of patents on ADI compositions of the authors with the identified average statistical composition was carried out. Directions for creating groups of economically alloyed ADI based on the concept of economical alloying are proposed.