Hi,
Yes, you can have B1s VM instance free for first 12 months. Note that Azure Free works differently than AWS. First 30 days you have $200 credit that you can use as you wish, then after that you have to convert to Pay-As-You-Go account and stick to free services to avoid charges.
Explore free Azure services
https://azure.microsoft.com/en-us/pricing/free-services/
Here is list of free services in table form from FAQ which is better reference than above link:
https://azure.microsoft.com/en-us/free/free-account-faq/#free-services
Azure free account FAQ
https://azure.microsoft.com/en-us/free/free-account-faq/
Please click Accept Answer if above was helpful.
Thanks.
-TP