The Portuguese, ranked 53rd, crushed his Italian opponent in the first set tie-break before wrapping up the second set by breaking to love in the 10th game.
Borges will face Ethan Quinn on Friday in the final four after the American defeated Czech Vit Kopriva 5-7, 7-5, 6-3.
Home favourite second seed Alejando Davidovich Fokina downed Grigor Dimitrov 6-3, 6-3, and will face Hungary's Fabian Marozsan after he eased past Miomir Kecmanovic 6-4, 6-3.