Fracturable support structure and method of forming the structure

A method of additive manufacturing, the method comprising:

• i) jetting droplets comprising a metal to form a first layer, the first layer comprising at least one material chosen from an article material, a support structure material and a fracturable material;
• ii) jetting additional droplets comprising the metal to form an additional layer on the first layer, the additional layer comprising at least one material chosen from the article material, the support structure material and the fracturable material;
• and
• iii) repeating ii) one or more times to form a three-dimensional build comprising an article and at least one support structure attached to the article at an interface, the interface comprising the fracturable material formed during one or more of i), ii) or iii), the fracturable material being formed by exposing portions of metal in at least one form chosen from the droplets, the additional droplets, the first layer and the additional layer with a reactant gas;
• and wherein:
• the fracturable material is a native non-metal comprising an oxynitride of the article material;
• and
• the reactant gas comprises a nitrogen-containing gas.