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Young's modulus-temperature and thermal expansion curves were measured in gamma-Fe-31Mn-(0.25-8.67) Si-0.77C (at%) alloys by dynamic audio resonance method and in a light dilatometer. The results show that the anomalies in Young's modulus and thermal expansion appear near the Neel temperature. The temperature coefficient of Young's modulus, (1/E(p))(dE(p)/dT), is controlled by Si content below the Neel temperature. When Si content increases to 5.31 at%, (1/E(p))(dE(p)/dT) is close to zero in temperature range from 260 to 335 K, i.e. the Fe-31Mn-5.31Si-0.67C (at%) alloy shows Elinvar character. The temperature range in which the Elinvar character appears is wider than that of gamma-Fe-Mn Elinvar alloys. The change in exchange energy and the Delta E effect result from the effect of Si on the antiferromagnetic behavior in gamma-Fe-Mn alloys since it induces or enhances localized magnetic moment. When the increase in normal Young's modulus due to lowering temperature is compensated by the Delta E effect caused by the antiferromagnetic ordering, Elinvar character appears. (C) 2011 Elsevier B.V. All rights reserved.