CHEN Yide 1, LIU Shujiang 1, ZHOU Yingying 1, ZHANG Houquan 2
(1. Key Laboratory of Processing and Testing Technology of Glass & Functional Ceramics of Shandong Province, Qilu Universityf Technology (Shandong Academy of Sciences), Jinan 250353, Shandong, China; 2. Tengzhou Comprehensive Inspection and Testing Center,Tengzhou 277500, Shandong, China)
Abstract: A series of calcium-aluminosilicate glasses were prepared by using melt cooling process. Hardness and cracking resistance (CR) of the glasses were studied by using Vickers indentation test. Structural evolution of the glasses were examined by using infrared spectroscopy and Raman spectroscopy, especially revealing the influence of SiO2 content and load on deformation and fracture behavior of the glasses. There are two deformation ways in the glasses during indentation: plastic flow and densification. Plastic (or shear) flow is a volume-conserved displacement, while densification is a non-volume-conserved irreversible compression that produces hemispherical regions with increased density beneath the indentation. When the SiO2 content was reduced, the glass has higher atomic packing density, lower molar volume and higher elastic modulus. Hardness of the glasses increases from 6.83 GPa to 7.22 GPa (load: 100 gf), but the fracture toughness is lowered and the anti-cracking ability is weakened. CR value decreases from 330 gf to 190 gf. On the contrary, with increasing content of SiO2, the densification process is more involved in the whole indentation process and the cracking resistance is enhanced, which is reflected in the indentation after annealing treatment. The recovery ratio of the indentation is increased, indicating the higher degree of residual stress reduction.
Key words: aluminosilicate glass; hardness; indentation