Two-phase (α + β) titanium alloys suffer from MTR formation in castings or after primary β or secondary (α + β) thermomechanical processing (TMP) that plays a role in the initiation of fatigue cracks. Room temperature lamellar or basketweave (α + β) colonies after casting or β processing are transformed to equiaxed, bimodal or duplex microstructure during secondary TMP via spheroidization of α lamellae. MTR formation in casting and β processing is related to β → α transformation wherein special prior β grain boundaries promote variant selection for GB α and lamellar α phases and produce large lamellar α variants on either side having identical orientation between them and with GB α phase. Within the bimodal microstructure, MTR forms after secondary TMP due to the orientation proximity between αs and αp phases wherein strong variant selection in β → αs phase within the transformed β regions compels them to follow the orientation of adjacent αp phase. Cold-dwell fatigue in high static applications stresses at moderate to low temperatures is linked to MTRs as being the crack initiation sites during dwell fatigue testing of titanium alloy engine components.