The only way that Qlik allows relations between tables is by having fields have exactly the same name.
It is our opinion that things should only have 1 name.
Within Qlik there is no such thing as primary key or foreign key. This has to do with the different way that Qlik handles data.
So, your solution:
Rename fields in your script, preferably in your preceding load:
wrongFieldName as RightFieldName,
If you left the thinking in SQL logics behind you it's not difficult to create working datamodels within qlikview - have a special look on the first 3 links in Get started with developing qlik datamodels but the other are of course helpful, too.