To export the DXF using "File > Export > AutoCAD DXF/DWG" to Teamcenter from NX, set the preference "TC_NX_DataExchange_Dataset_Preferences" with appropriate values. And under "Output File Destination" select the "Teamcenter" option.
Refer to the below NX documentation link for additional details on the preference "TC_NX_DataExchange_Dataset_Preferences".