Abstract: In this thesis, we study the chemical evolution of the Galactic disc using open clusters as tracers. The stars in a cluster are born from the same molecular cloud, and we can measure their distances and ages precisely. The study is part of the OCCASO project, which focuses on the precise measurement of elemental abundances.

High-resolution spectra (R > 60,000) were acquired over a wide wavelength range (400 to 900 nm) using the FIES, HERMES and CAFE instruments on the NOT, Mercator and CAHA2.2 telescopes, respectively. Up to 2023, 38 observing runs have been carried out, 21 of them in the course of this thesis. This has increased the number of observed clusters from 18 to 71. The sample has ages between 100 Ma and 7.25 Ga) and Galactocentric radial distances from 6.4 to 11.7 kpc. In addition, two clusters in the outer regions of the Galactic disc were studied using the MEGARA spectrograph on GTC.

Detailed analysis of atmospheric parameters and chemical abundances was performed by spectral synthesis and equivalent width. The chemical abundances of 25 elements were determined with high precision.

We studied the dependencies between abundance, position and age. We find positive dependencies between abundance and age in some α-elements. In the elements produced by neutron capture, we find that their trends with age are dependent on their percentage of production by s-process. We find the flattening of the [Fe/H] radial gradient only for clusters with ages older than 1Ga, suggesting that the flattening formation event occurred earlier. We also find that this gradient changes with age, being steeper for older ages. The [X/Fe] radial gradients of the other elements are compatible with no age dependence. The azimuthal gradient analysis shows hints of a positive dependence for clusters with ages between 2 and 7.3 Ga.

In the study of external clusters with MEGARA, unexpectedly low [Fe/H] values were identified, given their location on the disc. This suggests that they may not be affected by the flattening of the gradient, although further evaluation is required to confirm this.

Directors: Dr. Ricardo Jesús Carrera Jiménez and Dr. Laia Casamiquela Floriach

Tutor: Dr. Alberto Manrique Oliva