Will our family be able to use their phones abroad?

Hi
Our family has a Samsung Galaxy S3, A Nokia Lumia 520 and a Nokia Lumia 625. We are all under TalkTalk. We will be travelling to the USA AND Canada so is there a way that we can use our phones abroad. Will we have to purchase a forign sim card and will they be compatible with our phones.
Many thanks

Read more: Will our family be able to use their phones abroad?