Neil Armstrong Became A Muslim is a BIG, FAT Lie.

Did Neil Armstrong became a Muslim? 

According to the hoax, ‘When Louis Armstrong walked on the moon, he heard sounds in a strange language which he did not understand. Only later, after returning to earth, did he realize that it was actually the azaan’

So the answer is a big NO. Neil Armstrong didn't became a Muslim or was he converted to Islam.

According to Neil Armstrong himself, "I have found that many organizations claim me as a member, for which I am not a member, and a lot of different families — Armstrong families and others — make connections, many of which don’t exist. So many people identify with the success of Apollo. The claim about my becoming a Muslim is just an extreme version of people inevitably telling me they know somebody whom I might know."

Ref: James R. Hansen - First Man: The Life of Neil A. Armstrong - Simon & Schuster, 2005, pp 630-632, ISBN 9780743256315