Comment on "Origin of low-temperature shoulder internal friction peak of Snoek-Koster peak in a medium carbon high alloyed steel" by Lu et al. [Solid State Communications 195 (2014) 31]
We want to discuss the interpretation of low-temperature shoulder internal friction peak of Snoek-Koster peak (LTS-SK). Lu et al. (2015)  attributed it to the interaction between the carbon atoms and twin boundaries in martensite. Nevertheless, the decrease of the amplitude of LTS-SK peak due to carbon segregation is correlated with the interstitial carbon content in solid solution in martensite (Hoyos et al., 2015 ). Therefore, this peak can also be attributed to the presence of an internal friction athermal background, which is proportional to the concentration of interstitial carbon in solid solution (Tkalcec et al., 2015 [2,3]). In addition, they used an alloyed steel, in which epsilon carbide precipitated above of the LTS-SK peak temperature. As this behavior cannot be generalized for carbon and high alloyed steels, the carbide precipitates could made an additional contribution to the internal friction. (C) 2015 Elsevier Ltd. All rights reserved.