Not entirely. The database is most likely stored in a binary file, for which reason opening it in an ordinary editor will result in unreadable strange tokens. Inspecting the database however can be done, as with any database, with the proper database management tool. Simply Googling will usually result in a decent tool. This one looks promising and supports Excel export.
Note that exporting to excel using Mendix will usually be easier, as it allows to exports referred objects as well. Furthermore the database will not look exactly the same as your domain model, since names will differ (and be fully qualified) and references are stored in separate tables.