A new method of stepwise equilibration for molecular beam epitaxy (MBE) growth of relaxed, low dislocation-density Si1-xGex alloy layers on a (001)-Si substrate is presented. The stepwise buffer is prepared in a layer-by-layer manner. The growth of each layer includes two main stages, a low temperature stage and an average-temperature stage, which allows to separate the processes of nucleation and multiplication of misfit dislocations and thr propagation of the threading dislocations. An in situ equilibration annealing at considerably high temperature is implemented before the next growth step to remove the threading dislocations from the layer. The dislocation morphology in these stepwise graded Si1-xGex buffers is investigated by transmission electron and atomic force microscopy. The ability to grow fully strain relaxed, almost dislocation-free, virtual substrates of different compositions is demonstrated.