Microstructural Aspects of Some Magnesium Matrix Composites Reinforced with Amorphous/Nanocrystalline Ni-Ti Particulates

Abstract

Two magnesium matrix composites reinforced with 3 and 10% Ni-Ti particulates, respectively, were obtained by plasma sintering. The reinforcement material was obtained by grinding a mixture of powders of 68% Ni and 32% Ti atomic percent in a high energy mill for 40 hours. Particulates resulting from mechanical alloying have a partially amorphous and partially nanocrystalline structure, consisting of the following phases: Ni solid solution, Ti2Ni and NiTi (B2) phase. After sintering, both the matrix and the reinforcement material are nanocrystalline and the particulates have a polyphase structure, consisting of Ni(Ti), NiTi (R phase) and Ni4Ti3. The hardness of these composites is superior to the hardness of magnesium matrix composites reinforced with Ni-Ti particulates having 50% Ni / 50% Ti and 32% Ni / 68% Ti chemical compositions obtained under the same conditions and corresponding proportions of reinforcement material.