Is there any log available in Appian to see when a User is Created?

You can use the function User() please see the documentation below.
docs.appian.com/.../fnc_people_user.html

EXAMPLES
You can copy and paste these examples into the Expression Rule Designer to see how this works.

user("mike.smith","created") returns 12/20/05 10:36 PM GMT

Hello Chandu,

In our scenario, a some users have been activated and deactivated multiple times based on their current team/team.

Hi, Aidthya
AFAIK, I don't see any log that will hold of the User Activation and Deactivation History.
If you are using admin console, then we cannot track this activity.
If you are using any other website for user activation and deactivation then these can be tracked through DB.

Appian logs all user deactivation in log files - docs.appian.com/.../Logging.html

We have a shared component - community.appian.com/.../login-information-parser which parses log file. On similar lines a plugin can be written to get deactivation logs.

Also you can write a utility process model or use any shared component for activation and deactivation of user and allow users to perform those actions only through those and you can have logic to write audits in DB in process model.

Reference - community.appian.com/.../user-and-group-management-application

Appian logs all user deactivation in log files - docs.appian.com/.../Logging.html

We have a shared component - community.appian.com/.../login-information-parser which parses log file. On similar lines a plugin can be written to get deactivation logs.

Also you can write a utility process model or use any shared component for activation and deactivation of user and allow users to perform those actions only through those and you can have logic to write audits in DB in process model.

Reference - community.appian.com/.../user-and-group-management-application