(Adds details) ROME, May 12 (Reuters) - Belgium's Tim Wellens broke away alone to win the sixth stage of the Giro d'Italia as the peloton negotiated the first real climbs of the race on Thursday. Two days after his 25th birthday, Lotto-Soudal rider Wellens was with a five-man breakaway before sprinting clear on the climb towards the finish line on top of the Aremogna. It was the first Grand Tour stage victory of his career and followed team mate Andre Griepel's win on Wednesday. More...