I wonder if the presence of a gravity field, makes any difference in the properties of the finished parts? That’s only if we can somehow, keep every other factor almost the same.
In theory yes! But how much difference does it make, it depends on the impurities, material, and of course size of the part.
Right after filling the mold, the metal is still a fluid, it means the heat transfer is carried out by conduction, (natural)convection and radiation.
In the presence of a gravity field, the temperature gradient and the density difference cause fluid motion, and so we can talk about natural convection.
In absence of gravity there is no natural convection, so the finished part is much more uniform than that casted inside a gravity field. (Heavy elements can randomly take place anywhere, rather settling down at the bottom of the mould).
There is another issue:
As the conduction and convection are almost non-existence in microgravity, the only way that the metal fluid can dissipate the heat and solidifies is by radiation. This is going to prolong the time required for solidification.
If the part is steel, then, the extended time will definitely changes the properties of the finished part.
It certainly does: any slag inclusions, for example, will tend to rise to the "top" surface of the casting, which hence furnishes an anisotropic distribution of inclusions in the finished part that depends on gravity.
If the sprue or gate that feeds molten metal into the mold cavity is on the "top" side of the mold, then breaking the gate remnant off the finished part is one way of eliminating flaws in it.