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Effect of Thermal Vacancy on Thermodynamic Behaviors in BCC W Close to Melting Point: A Thermodynamic Study

by Ying Tang 1,* and Lijun Zhang 2,*
1
School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130, China
2
State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China
*
Authors to whom correspondence should be addressed.
Materials 2018, 11(9), 1648; https://doi.org/10.3390/ma11091648
Received: 28 July 2018 / Revised: 25 August 2018 / Accepted: 3 September 2018 / Published: 7 September 2018
As temperature increases, the thermal vacancy concentration in pure metals dramatically increases and causes some strongly non-linear thermodynamic behaviors in pure metals when close to their melting points. In this paper, we chose body-centered cubic (bcc) W as the target and presented a thermodynamic model to account for its Gibbs energy of pure bcc W from 0 K to melting point by including the contribution of thermal vacancy. A new formula for interaction part was proposed for describing the quadratic temperature behavior of vacancy formation energy. Based on the experimental/first-principles computed thermodynamic properties, all the parameters in the Gibbs energy function were assessed by following the proposed two-step optimization strategy. The thermodynamic behaviors, i.e., the strong nonlinear increase for temperature dependence of heat capacities at high temperatures and a nonlinear Arrhenius plot of vacancy concentration, in bcc W can be well reproduced by the obtained Gibbs energy. The successful description of thermal vacancy on such strongly non-linear thermodynamic behaviors in bcc W indicates that the presently proposed thermodynamic model and optimization strategy should be universal ones and are applicable to all other metals. View Full-Text
Keywords: thermal vacancy; thermodynamics; heat capacity; bcc tungsten thermal vacancy; thermodynamics; heat capacity; bcc tungsten
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Tang, Y.; Zhang, L. Effect of Thermal Vacancy on Thermodynamic Behaviors in BCC W Close to Melting Point: A Thermodynamic Study. Materials 2018, 11, 1648.

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