You can make a docking mechanism out of any material which will meet your requirements. These requirements will be dependent on many factors, but probably the most significant will be how much mechanical load it will have to bear. Aluminum is actually a very popular metal in spacecraft construction, including for docking mechanisms, because it has a good blend of strength and low mass. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em> -- The Tenth Doctor, "Blink"</font></p> </div>