We present detailed elemental abundances of 12 subgiants in the open cluster IC 4756 including Na , Al , Mg , Si , Ca , Ti , Cr , Ni , Fe , Zn and Ba .
We measure the cluster to have [ Fe/H ] = -0.01 \pm 0.10 .
Most of the measured star-to-star [ X/H ] abundance variation is below \sigma < 0.03 , as expected from a coeval stellar population preserving natal abundance patterns , supporting the use of elemental abundances as a probe to reconstruct dispersed clusters .
We find discrepancies between Cr i and Cr ii abundances as well as between Ti i and Ti ii abundances , where the ionized abundances are larger by about 0.2 dex .
This follows other such studies which demonstrate the effects of overionization in cool stars .
IC 4756 are supersolar in Mg , Si , Na and Al , but are solar in the other elements .
The fact that IC 4756 is supersolar in some \alpha -elements ( Mg , Si ) but solar in the others ( Ca , Ti ) suggests that the production of \alpha -elements is not simply one dimensional and could be exploited for chemical tagging .