This depends on what reference frame you are looking at.
From the viewpoint of someone sitting on the disk and riding along with it - i.e. like a kid on a merry-go-round (though sadly it seems such have been removed as a result of creeping mullycuddle but that's neither here nor there) - then yes, indeed the increase in distance of the particle from the disk's center is accompanied by a measurable acceleration and thus by Newton's second law reflects the presence of a force.
From the viewpoint of someone sitting on the ground or at least not rotating with the disk, the body moves in a straight line, with constant speed (i.e. ignoring other forces like gravity) after it is released. In this frame, there is no force after the body is released because in straight-line uniform motion there are no forces acting pretty much by definition, instead its distance increases from the center simply because it is moving away. But before it was released, and when it was circling on the disk there was a force - namely that which is accelerating it on its curvilinear path - and then when the ball was released, that force stopped.
In fact, the latter force is present in both scenarios. In the first scenario, the person sitting on the disk, were sie to be holding the object, would have attributed it to having to "try to pull it tight to keep it from 'wanting to fly away'". Since this is an actual exertion by hir own muscle power, both observers must agree it's happening since such a thing cannot be just made to go away by a simple coordinate transform, requiring a complex rearrangement of molecules in muscles, brains, etc. . Thus it must be a real force, and that force is the same one which in the second scenario is being exerted - in the same direction, i.e. toward the center - to keep deflecting its velocity around the circle.
The only difference is that due to the different vantage point, one interprets it as trying to "keep the ball from fleeing" while the other thinks it is exerted to "deflect it from its straight line motion".
Since in only one observation the outward force is noted, while in both the inward force is noted, we like to say the inward force is the "real" force since it represents an actual interaction, while the other represents the artifact of a coordinate transform.
But nonetheless, both are equally valid ways of looking at the same scenario, and both can be reconciled by noting that for the person sitting on the disk hir situation of forces must be different because to hir sie is stationary, while in the case of the external observer sie is moving. Nonetheless, the same motion, same exertions and other invariants must be preserved between both. I suppose there is some philosophic issues involved here, as there always will be when you dig into it, but this is basically the reasoning behind one common philosophic view and at least behind the apparently differing observations and their relation which you will still have to accommodate no matter your philosophy of "reality" (i.e. ontology).
And yes, for the question, this outward force seen by the observer standing on the disk is centrifugal force. Whether it's a "real force" or not is not relevant to that - that is the name which refers to that particular thing.