German silver falls into the category of metals known as non-ferrous (google ferrous and non-ferrous metals). My experience has taught me as a rule of thumb Non ferrous metals fail when bent or attempted to be altered when they are hot. Non-ferrous metals should be bent cold, ferrous metals bent hot If the casting is good then the nickel (german silver) should be ok if you anneal it by heating to a dull red then allow it to cool and quench when the red goes away. If the casting breaks when you try to take a slight twist out it I would say that you have a bad casting meaning the metal was contaminated in some way. There are any number of factors that contribute to contamination of metal during melting. Some of these factors can occur if there is too much oxygen that binds with the molten metal or it has been overheated or some of the alloys in the metal have been reduced. During investment casting and possibly sand casting you can get a temperature spike that over heats the investment or the sand, it melts the flask material and causes gas to shoot through the poured metal causing porosity, the phenomenon is known as " gassing off". If you are concerned call the supplier and inform them of your issue ask them if you can exchange the part if the casting fails or would they prefer to send you another part that is not twisted.
