Welding a genesis V2100 walmart bike frame

[steelmesh]

If I tig welded some stuff on the downtube of this frame and rear-lower suspension with some 4043 filler, any comments about what I am planning to do? Like, is that some fake alum alloy or something.

http://www.walmart.com/ip/Genesis-26-Men-s-V2100-Dual-Suspension-Bicycle/14089739?adid=bzv_fb_revshr_001

Thank you in advance.