Oxygen-free Copper Impact Of The Melting Characteristics Of The Experimental Study

Melting properties of materials at shock compression are of particular importance in the equations of state. Copper as a representative of transitional metals is one of important standard materials with intermediate shock impedance in shock wave experiments .Hence, the confirmation of the solid-liquid phase boundary for copper is of geat significance to the design of Hugoniot erperiments , especially to the devise of the unloaded path measurements and the analyses of results.The high-pressure sound velocity data show that for copper, the melting on Hugoniot begins near 232GPa and the complete melting occurs about 265GPa . The temperatures corresponding to the onset and completion of melting on the Hugoniot were calculated by thermodynamics method, no experimental data of the shock melting temperatures are available under shock compression up to now. Using the shcok-release model , we calculated the fraction of melted mass Xm, the ratio TI/Tm of the interfacial temperatures to the melting temperatures, and so on for the representative Cu/LiF assemblys at shock and release pressures. The results of melting calculations indicated that the interfacial temperatures TI can be derived with the Gover model and the melting temperatures Tm can not be gained via the interfacial temperatures from the experiments in the case of no melting . If the state of intial shock or interfacial release is located in a solid-liquid mixed phase region or adjacent to the liquidus, TI-Tm as Xm-1. In this work, confront to the traditional film-depositting on window, a setup of bulk copper-sample closely contected with LiF-window was employed.the apparent Cu/LiF interface temperature was measured using optical radiometry techniques. The interfacial temperature can be regarded as the melting temperature at the interfacial pressure in the case of shock or release melting assesed by the energy principle and the high-pressure sound velocity data. If no shcok or release melting occurs , the additional temperature resulted from the high-temperature layer under shock compression was deducted from the observed interfacial temperature based on "the heat conduction model for three layers", and the real interfacial temperature corresponding to the situation of ideal interface was obtained . And then the shock temperature of oxygen- free copper sample was derived. The melting temperature data for this work are in agreetment with the results from both high-pressure sound velocity measurements and theoretical calculations . The melting properties of oxygen-free copper at high pressure can be approximately described by the Lindemann melting law. The shock temperature measured at relatively lower pressure was consistent with the result from thermodynamic calculations.The main outcome of this work preliminary confirms the feasibility of the experimental method by contacting closely of bulksample with window. This method may provide a potential approach for shock-induced melting temperature or Hugoniot temperature of metals.