The aim of this thesis is to investigate the influence of ageing process on the microstructure and mechanical properties of aluminium-silicon alloys. The investigation was carried on Al-9%Si-3%Cu and Al-9%Si-0.4%Mg. To obtain different DAS with low content of oxide films and micro shrinkage, gradient solidification has been used. The specimens were treated according to T6 heat treatment. In this thesis it has been shown that solidification rate has great influence on mechanical properties since it controls microstructure. To reach peak level of mechanical properties different times of artificial ageing were used depending on the alloy. In peak value condition Yield’s Strength of alloys was 197MPa for Al-Si-Cu alloy and 243MPa for Al-Si-Mg one. These results can be compared to these presented in other papers concerning aluminium silicon alloys. Such comparison shows that when talking about potential of alloy, these results are more or less the same as in other articles in this field. The work was conducted within 10 weeks and for this reason not all the necessary data was collected. Further work will be conducted to obtain missing results, like overaged state for Al-Si-Cu alloy.

<p>The aim of this thesis is to investigate the influence of ageing process on the microstructure and mechanical properties of aluminium-silicon alloys. The investigation was carried on Al-9%Si-3%Cu and Al-9%Si-0.4%Mg. To obtain different DAS with low content of oxide films and micro shrinkage, gradient solidification has been used. The specimens were treated according to T6 heat treatment.</p><p>In this thesis it has been shown that solidification rate has great influence on mechanical properties since it controls microstructure. To reach peak level of mechanical properties different times of artificial ageing were used depending on the alloy.</p><p>In peak value condition Yield’s Strength of alloys was 197MPa for Al-Si-Cu alloy and 243MPa for Al-Si-Mg one. These results can be compared to these presented in other papers concerning aluminium silicon alloys. Such comparison shows that when talking about potential of alloy, these results are more or less the same as in other articles in this field.</p><p>The work was conducted within 10 weeks and for this reason not all the necessary data was collected. Further work will be conducted to obtain missing results, like overaged state for Al-Si-Cu alloy.</p>

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Microstructure and micro-mechanical characterization of as-built and heat-treated samples of Hastelloy X produced by laser powder bed fusion (LPBF) process has been carried out in this study. As-built LPBF blocks were solution heat-treated at 1177°C and 1220°C followed by fast cooling. The microstructure of as-built and heat-treated samples were studied by light optical microscopy, scanning electron microscopy, and electron backscatter diffraction. Instrumented indentation micro Vickers testing was performed to obtain microhardness and elastic modulus of asbuilt and heat-treated samples. Microtensile samples from as-built and heat-treated blocks were prepared and polished for mechanical characterization. Microtensile testing inside the scanning electron microscope was performed to evaluate the mechanical properties and to get information about the microstructural changes during plastic deformation. Microstructure characterization revealed disrupted epitaxial grain growth for the as-built samples whereas the two heated-treated Hastelloy X samples exhibited equiaxed grains with varying twin fractions. As-built Hastelloy X samples exhibited higher mean hardness than heat-treated samples. The yield strength of as-built samples reveals higher values as compared to conventional wrought Hastelloy X samples, whereas lower yield strength and higher elongation were observed for heat-treated samples as compared to as-built samples. Higher elongation and lower yield strength values were observed for the samples solution heat-treated at 1220°C compared to the solution heat-treated at 1177°C. Microstructural evaluation at different plastic strains during in-situ microtensile testing reveals a clear difference in dislocation density for as-built and heat-treated samples.