دانلود رایگان مقاله مدول الاستیک تیتانیوم نانوکریستالین ارزیابی شده

Abstract

The present study is devoted to examinations of the elastic modulus with the use of the uniaxial tensile test. The commertial purity titanium Grade 2 in the two states i.e. microcrystalline (mc-Ti) and nanocrystalline (nc-Ti) were examined. Bulk nc-Ti was fabricated by hydrostatic extrusion (HE) which is one of the severe plastic deformation methods (SPD). The elastic modulus of mc-Ti and nc-Ti were compared with the aim to analyze the influence of the nanostructure of titanium on its elastic modulus. The mc-Ti and nc-Ti samples were subjected to uniaxial tensile tests at various strain rates and various values of stress. Generally, higher elastic modulus values were obtained in microcrystalline titanium. The elastic modulus of mc-Ti was evaluated at 107 GPa on average, whereas the elastic modulus of nc-Ti was 94 GPa on average. The nanocrystalline titanium had a lower elastic modulus than its microcrystalline counterpart by 13% on average, which can be attributed to the presence of significant volume of amorphous regions in the structure. Moreover, in this case a lower standard deviation of all the results was obtained. In most cases, with higher applied stress (load) the value of the modulus was lower, whereas at higher strain rates its value was higher.

5. Summary and conclusions

Titanium in the microcrystalline state (mc-Ti) with an average grain size of 20 mm and the titanium in the nanocrystalline state (nc-Ti) with an average grain size of 55 nm were investigated. The nc-Ti was characterized by enhanced mechanical properties such as microhardness, yield stress and ultimate tensile strength. The aim of this study was to examine the elastic properties of both these states and to determine the influence of their structure on the Young's modulus. The elastic modulus was determined by the uniaxial tensile tests using standard samples. Based on the results obtained it can be concluded: 1. The values of the elastic modulus obtained for microcrystalline titanium (mc-Ti) are in agreement with the literature data. 2. Irrespective of the test parameters, all the values of the elastic modulus obtained for nc-Ti were slightly lower (by about 13%) than those of its microcrystalline counterpart. 3. The intensive growth of amorphous regions in the structure, such as grain boundaries or dislocations, affects the elastic properties of titanium. 4. Strain rate affects the value of the elastic modulus of titanium Grade 2 evaluated by a tensile tests. 5. Value of the stress insignificantly affects the value of the elastic modulus.