Razvoj mikrostrukture pri izdelavi gradientnega materiala H13-Cu s tehnologijo LENS : doktorska disertacija

slovenian

doktorska dela

2014

Univerza v Mariboru, Fakulteta za strojništvo

LENS technology represents a modern additive technology for the application of metallic materials. In this dissertation, the conceptual design of the use of high-tech materials is presented in tools for injection moulding as well as tools for die casting of light metals fabricated with this technology. In practice, deviations of dimensional and design tolerances of the product frequently occur during the solidification due to uneven temperature distribution in the tool and consequently, in the product during cooling. At the same time, thermal conductivity of tool steels limits the cooling time and consequently, the productivity of tools. The presented problem of synthesizing a H13 tool steel and copper alloy using functionally graded materials with specific microstructure and a combination of properties represents new possibilities for optimization in this field. The dissertation shows the influence of the layered deposition and thermal conditions of the LENS technology on the development of microstructure and consequently, mechanical properties. For easier understanding, we characterized reference samples of different chemical compositions using the traditional casting technology. Using various analyses, such as microstructural, chemical, thermal and phase, we determined phase compositions as well as the impact of technology on the formation of cracks and the development of microstructure, depending on the chemical composition and solidification conditions. In the field of chemical compositions which are susceptible to cracking, we examined the crack-filling mechanism, which is a result of complete wetting of copper and temperature conditions during the deposition of new layers. To examine the effects of phase compositions on mechanical properties of the alloys, tensile tests and microhardness measurements were carried out. Results show the possibility of a successful fabrication of samples of functionally graded materials H13-Cu using the LENS technology. Finally, the influence of solidification conditions on microstructure development as well as the model of microstructure development and stability are explained.

08.08.2023