A Study of Effects of Precipitation Hardening of Low-Alloy Copper-Nickel Spheroidal Cast Iron

Abstract

One type of spheroidal cast iron, with additions of 0.51% Cu and 0.72% Ni, was subjected to precipitation hardening. Assuming that the greatest increase in hardness after the shortest time of ageing is facilitated by chemical homogenisation and fragmentation of cast iron grain matrix, precipitation hardening after pre-normalisation was executed. Hardness (HB), microhardness (HV), qualitative and quantitative metalographic (LM, SEM) and X-ray structural (XRD) tests were performed. The acquired result of 13.2% increase in hardness after ca. 5-hour ageing of pre-normalised cast iron confirmed the assumption.

Rule modeling of ADI cast iron structure for contradictory data

“…Examples of such scattered measurements can be found in (Olofsson et al, 2011), where at the hardening temperatures of 250°C, 300°C, 350°C and 400°C and during 1 h, elongation in the following ranges was recorded: 1 -5%; 3 -4%; 5 -10.5% and 7.5 -10%, and for the 2 h time: 1 -1.5%; 3 -4.5%; 3 -7% and 4 -9%. In turn, the measurement of impact toughness is strongly determined, among others, by: the place where the samples were cut (Szykowny et al, 2010), the orientation of the samples (Chawla et al, 2008) and the method of sample preparation (Nobuki et al, 2010). The paper by Szykowny et al (2010) shows the influence of the distance of the notch from the top surface of the mold.…”

“…In turn, the measurement of impact toughness is strongly determined, among others, by: the place where the samples were cut (Szykowny et al, 2010), the orientation of the samples (Chawla et al, 2008) and the method of sample preparation (Nobuki et al, 2010). The paper by Szykowny et al (2010) shows the influence of the distance of the notch from the top surface of the mold. According to Chawla et al (2008), the direction of cutting out the impact specimens is important, as crack propagation always starts with the graphite spheroid, but continues along the austenite-ferrite boundary.…”