Fabrication and Mechanical Properties of Nb-Ni-Al Ternary Intermetallic Particle-reinforced Al Matrix Composite

• Main Authors: Bing-Yih Lin, 林秉毅
• Other Authors: Hsin-Ming Wu
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/12651593467701012416

碩士 === 大同大學 === 材料工程學系(所) === 99 === In this study, aluminum matrix composites (AMCs) reinforced by Nb-Ni-Al ternary intermetallic particle was prepared by mechanical alloying. The first phase of this study selects appropriate Nb, Ni, and Al compositions based on the Nb-Ni-Al ternary equilibrium diagram to synthesize Nb(Ni,Al)2 Laves and NbNi2Al Heusler powders by mechanical alloying and subsequent annealing treatment. The phase transformation and morphology characteristics of the as-milled and heat-treated powders were studied by using XRD and SEM. In the second phase, the synthesized Laves phase and Heusler phase powders were, respectively, blended with additional Al powder and subjected to further milling for 30 min and vacuum hot-pressing at 500 ℃, 80 MPa for 1 h to produce AMCs contain different volume fractions of Laves and Heusler strengthening phases. The effect of volume fractions of strengthening phases on microstructures and mechanical properties of AMCs were investigated. The results indicate that Laves phase and Heusler phase powders cannot be synthesized directly from elemental powders by mechanical alloying, but can be obtained after annealing on the as-milled powders for 1 h at 1200 ℃ and 800 ℃, respectively. With the increase of milling time, the particles of the heat-treated powders were decreased in size and revealed spherical morphology. The vacuum hot-pressed bulk composites consolidated from the further milling blended powders exhibit grain refinement in bulk composite as well as the refinement and homogeneity of the strengthening particles, as compared to the bulk composites made from unmilled blended powders. As the strengthening phases increase, the measured hardness of AMCs increases and the relative density decreases. With the addition of 40 vol.% Laves and Heusler phases, the hardness of the bulk composites increases to 259 Hv and 273 Hv, respectively.