28.1 Complete the extract from a technical document about welding using the words in the box. You will need to use some words twice. Look at A opposite to help you.

It is possible for components made of different metals to be (1) welded. For instance, steel can be welded to copper and to brass. However, it is much more difficult to weld components made of two (2) dissimilar than it is to weld those made of the same (3) materials. While there is no difficulty in melting two different metals and mixing them together in a (4) molten state, problems occur once the hot, liquid metal forming the (5) pool starts to cool. As this process takes place, the two metals will not necessarily (6) fuse properly. Once the joint has cooled, this can result in (7) discontinuities such as cracks, at the heart of the (8) weld. In addition, as the metals contract at different rates (due to different coefficients of thermal expansion), powerful (9) residual stresses can build up, not only in the joint, but also in the wider (10) heat-affected zone near the joint.