Microphase separation in crosslinked diblock copolymers is investigated with a time-dependent Ginzburg-Landau model. Upon separation, polymers originally crosslinked in the homogeneous phase elongate parallel to the composition gradient. We take into account this elastic coupling as well as the random stress caused by the disordered network structure. The phase ordering process is numerically simulated to study the domain morphology. The random stress destroys the long-range orientational order of lamellae and creates jagged interfaces, which give rise to an asymmetric peak in the structure factor.