Aluminum　alloy　7075　(with　7055　and　7150　filler　wires)　was　welded　using　a　digital　welding　machine　that　can　switch　arc　mode　between　MIG,　CMT　and　CMT+P　modes.　The　transverse-motion　weldability　test　of　joints　welded　under　different　arc　modes　showed　that　the　solidification　cracking　susceptibility　was　lower　in　CMT-technique-based　welds　than　in　MIG　welds.　The　temperature　cycle　of　the　welding　pool　under　different　arc　modes　was　recorded　using　mini-thermocouples,　which　showed　that　the　cooling　rate　was　lower　in　CMT　welded　samples　than　in　MIG　welded　samples.　The　low　cooling　rate　promoted　the　growth　of　alpha-Al　dendrites　through　the　back　diffusion　effect.　Electron　probe　micro-analysis　showed　that　micro-segregation　of　the　alpha-Al　dendrites　was　lower　in　the　CMT　welded　samples　than　in　the　MIG　welded　samples.　The　T-(f(Al))(1/2)　curve　of　each　weld　was　calculated,　which　showed　that　CMT-based　welding　enhanced　the　bridging　of　adjacent　alpha-Al　dendrites,　reducing　the　tendency　for　solidification　cracking.