The Use of the Mechanochemical Method for Obtaining Modifiers of In-mold Copper Modification
A. A. ZHDANOK1, V. A. KUZNETSOV1,2, B. P. TOLOCHKO1, Z. A. KOROTAEVA1, N. V. STEPANOVA2, K. A. SKOROKHOD2
1Institute of Solid State Chemistry and Mechanochemistry, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
2Novosibirsk State Technical University, Novosibirsk, Russia
Keywords: in-mold modification, modifier, casting, copper, ultrafine ceramic particles
Pages: 226-235
Abstract
The main properties of copper that determine its preferable application areas are high electrical conductance and thermal conductivity, as well as high stability against corrosion. The mechanical characteristics of metals may be affected by introducing trace additives of inert ceramic materials (modifying agents), which would be crystallization centres, altering micro- and macrostructure. For better wetting with the melt, ceramic particles are to be plated with metals through the joint treatment of ceramic powders and metals in planetary centrifugal activators. To study the effect of modification on copper properties, four molds were prepared to obtain cylindrical samples 30 mm in diameter, with different modifying agents: 1) B4C/Cu/Cr, 2) (WC/TiC)/Cu/Cr, 3) ferrocerium MTs50Zh6 (an alloy of iron and a mixture of rare earth metals), 4) without additives. The amount of the active phase (ceramics and rare-earth metals) was 0.03 wt. % of the cast mass. It is discovered that samples 1 and 2 exhibit the smallest standard deviations of hardness from the mean values, which may be the sign of more uniform crystallization of the melt in the cases when B4C and WC/TiC are used as modifying agents. Standard deviations for samples 1-4 with respect to HBW (Brinell hardness) are 1.90, 1.37, 6.29, 2.54, respectively, and with respect to HV (Vickers hardness) - 2.39, 2.89, 6.53, 5.28, respectively. The improvement of corrosion stability in comparison with non-modified sample after exposure for 43 h in 11 % HNO3 solution was 9.3, 2.2, -10.9, 0.0 %, respectively, and after exposure for 127 h - 13.1, 15.4, 14.6, 0.0 %, respectively. The grain size of samples modified with ceramic refractory particles decreased by a factor of 2.4-3.0 in comparison with the reference sample, while the grain size of samples modified with rare-earth metals, on the contrary, increased by a factor of 1.5-1.7. The size of subgrains in all the modified samples was 1.3-5 times smaller than that in the reference sample.
DOI: 10.15372/CSD2022377
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