Merging uncompleted torrent files

Is it possible to merge two of the same uncompleted torrent files.? eg. I download a torrent that has 2 pieces but i only download the first piece and my friend downloads the second piece. Is it possible to merge these two files so that I have a completed torrent.

Yes, you can do that with torram utility. It recontructs the torrernt's download directory using any number of partially or fully downloaded files. So if your files both are somewhere in ~/Download/Torrents/ you can use:

torram -c -o <the_directory_where_to_put_reconstructed_files> <yourtorrentfile.torrent> ~/Download

No matter where exactly your files live - just specify any directory that parent for both of them (that's why I used ~/Download/ in the example). If you not sure you can even use '/' as the last arg - the tool scans the directory recursively, finds candidates by file size, checks their chunks by md5 hash and merges every found good pieces into final file.

I am not sure if your question is just theoretical or a real problem... going to answer as theoretical...

As long as the full file completed, technically yes - I am not entirely sure of the best program to actually accomplish this.

A better solution may be to download the .torrent file and modify it to a private tracker between you and your friend so you complete off of each other.

If you have one torrent file that two separate people were downloading on different systems, and want to bring what person B has downloaded to person A's system, the straightforward and obvious thing is to just copy B's files to A's torrent directly and then resume the torrent on person A's system. All Bittorrent peer programs I've used will scan files when they start to figure out where they are at in the file. So resuming from files is not an issue.

But - this will help you only if the torrent consisted of a number of files and person B had a number of complete files, or a number of incomplete files that A did not start downloading.

If you overwrite person A's files with files of the same name from person B, you won't "combine" what is already downloaded between them, you'll be where person B left off with that file.

If your torrent is simply a very large single file, this won't help you, you'll simply be taking over where B left off the download.

Otherwise look into mergetorrent as suggested by @Alexey Markov in the comments. I haven't used this utility but it seems to do what you want.