Relaxed Si_1-xGe_x layers with germanium contents of 0.04, 0.13, 0.24 and 0.36 have been grown by MBE and implanted under tightly controlled conditions with 2 MeV Si⁺ ions over the dose range 1×10¹⁰ to 5×10¹⁰ Si⁺ cm^-2. The introduction rate and characteristics of simple defects have been investigated by EPR and DLTS whilst the accumulation of this damage with increasing dose has been followed by RBS, XTEM and optical depth profiling up to the onset of amorphisation. It is found that the integrated damage increases whilst the critical dose for amorphisation decreases with increasing Ge content.