lomapaeso
To add to your explanation to radken: Assuming the disc began to stretch, because of overspeed and presence of higher than designed for temperatures in the bore area, the turbine blades could have started to unlatch at the tip shrouds. Since the tip shrouds provide blade dampening, it would have been the beginning of the end for the turbine blades very quickly, even without any contact with other adjacent components. The extreme unbalance created would be catastrophic to the disc already operating beyond its design capability.