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tokens: the age-metallicity relation for stars in the solar neighbourhood 3 is often explained as due to radial mixing of stars in a Galactic disk with a gradient in [Fe/H]; stars presently in the solar neighbourhood were born at different Galactocentric distances (). However, in order to explain the low scatter in Mg/Fe and Y/Mg at a given age, the gradients in these abundance ratios should then be vanishingly small at all times, which requires that the ratios between the number of Type II SNe, Type Ia SNe, and AGB stars have evolved in the same way independent of . This corresponds to a weak or non-existent inside-out formation history of the Galactic disk ( Haywood et al. 2015 ). 4.2. 16 Cyg A and B Among the Kepler stars included in this paper, the two components of the 16 Cyg binary system are of particular interest. The very detailed set of oscillation frequencies for these relatively bright stars has made it possible to derive precise values of masses, radii and ages ( Metcalfe et al. 2015 ), He abundances ( Verma et al. 2014 ), and rotation periods ( Davies et al. 2015 ). Furthermore, a comparison of the seismic radii with those determined from interferometric angular diameters ( White et al. 2013 ) provides an important test of asteroseismology (see Silva Aguirre et al. 2017 ). The chemical compositions of 16 Cyg A and B are also very interesting. Cochran et al. (1997) discovered that 16 Cyg B has a Jupiter-sized planet with a mass in an eccentric orbit with a period of 800 days, whereas no planets have been detected around 16 Cyg A . Hence, a comparison of abundances of the two stars has the potential of revealing possible effects of planet formation or planet accretion on stellar surface composition as discussed by Laws Gonzalez (2001) , who in a high-precision spectroscopic analysis found a small metallicity difference, (A – B) = , between 16 Cyg A and B. This was supported by Ramírez et al. (2011) , who found systematic differences of the abundances of the two components corresponding to a mean difference of (A – B) = for 22 elements. However, in a similar study by Schuler et al. (2011) , the mean abundance difference for 15 elements was found to be only dex. In order to clarify the controversy about the chemical compositions of 16 Cyg A and B, Tucci Maia et al. (2014) made a new high-precision spectroscopic analysis using CFHT/ESPaDOnS spectra with and . From a strictly differential analysis of the two stars, they obtained (A – B supporting the abundance difference found by Ramírez et al. (2011) . Furthermore, they found the abundance difference between A and B to increase with elemental condensation temperature for the refractory elements, and interpreted this as a signature of sequestration of refractory elements in the core of the giant planet around 16 Cyg B . Table 4 Comparison of atmospheric parameters and [Fe/H] for 16 Cyg A and B between Tucci Maia et al. (2014) and this paper. Notes. (a) Tucci Maia et al. (2014) . (b) This