If you would like to use AWS for free then you might have to compromise cluster nodes to t2.micro and the total EBS (Elastic Book Store) to only 30 GigaBytes. This kind of approach has low-quality hardware performance.
The Amazon Web Services are programmed in such a way that they provide free services only to t2.micro and that too to a limited time period of 750 hours which can be brought down as, say 10 nodes per 75 hours beyond which you would be charged accordingly.