Excel, by default, saves all files in the folder: C:\Users\*username*\Documents. To change this, in the Ribbon, go to File > Options.
In the Excel Options screen, choose Save.
Then change the Default local file location (under Save Workbooks) to the desired directory.
Excel files are now, by default, saved in the new folder specified in Excel Options.
From: How to Change the Default Directory in Excel - Automate Excel