We had the same problem with Duplex and Titanium on a project that we just finished using CAESAR 5.00.

Our problem was not the upper temperature limit, but the lower. For these materials, the CAESAR data base did not have expansion coefficients below 70 deg. F. (21.1111 def. C.) This may be your problem too.

We solved this by creating our own material data bases to cover the range of temperatures that we needed. Unfortunately, this information is not readily available. We used educated guessing and extrapolation to get the numbers.

Good luck.