A method of joining two components to form a product

A method of forming a product from a first component comprising a void region filled with a salt by joining the first component to a second component using pressure and then removing the salt by melting. Figure 1 shows an aerofoil blade 1 with a plurality of passages 3. The passages 3 are filled with a powdered salt 4 and then welded closed. An end of the blade 1 is located in an end of a mould 2 which is filled with a powdered alloy 6. The blade 1 and mould 2 are hot isostatically pressed, thereby sintering the powder 6 and joining it to the blade 1. The welds 5 are then opened and the salt 4 removed. Figure 2 shows powder preform 26 which comprises a cavity 23. A reinforcing box, web, rib or mesh 20 lies within the cavity 23, along with a salt 24. The perform 26 is hipped and then the salt 24 removed through a drain hole 28 drilled into the body. An alloy may be used instead of a salt.