Niobium Carbide-Reinforced Al Matrix Composites Produced by High-Energy Ball Milling
- PDF / 3,475,838 Bytes
- 9 Pages / 593.972 x 792 pts Page_size
- 74 Downloads / 292 Views
NTRODUCTION
PRECIPITATION hardening is the most effective mechanism for the large-scale production of highstrength, aluminum-based materials, to be used as a lightweight solution for structural applications. These applications are mainly driven by the automotive and aerospace industries. The resulting nanoscale precipitates, homogeneously distributed into the Al matrix through optimized thermomechanical processing of commercial Al-based alloys, increases the strength up to 10 times when compared with pure annealed aluminum. Nevertheless, this strengthening potential is limited by alloying elements’ solubility into the Al in a near-equilibrium thermodynamics condition.[1] Furthermore, the low thermal stability of such precipitates limits high-temperature applications as they can grow or dissolve during long exposition to intermediate temperatures. One alternative to obtaining high-performance, Al-based materials is the production of metal matrix composites (MMCs), more specifically, aluminum matrix composites (AMCs). In fact, interest in production of MMCs started in 1970 to 1980 driven by U.S. military programs demanding high-performance DILERMANDO NAGLE TRAVESSA, MARINA JUDICE SILVA, and KA´TIA REGINA CARDOSO are with the Instituto de Cieˆncia e Tecnologia, Universidade Federal de Sa˜o Paulo. Talim 330, Vila Nair., Sa˜o Jose´ dos Campos, SP 12231-280, Brazil. Contact e-mail: [email protected] Manuscript submitted September 21, 2016. Article published online March 28, 2017. 1754—VOLUME 48B, JUNE 2017
materials.[2,3] Cost issues were secondary at that time, and the interest was mainly in continuous fibers or whisker-reinforced Al or Ti matrix composites. In the decade of 1990, however, the military interest for such MMC decreased, and for general industrial purpose, cost issues became important. As a consequence, the interest changed to low-cost particulate ceramic materials available in abundance thanks to the growing abrasive industry. The particles of SiC and Al2O3 started to be investigated as a reinforcing phase for metals. At the same time, Al became the best candidate for the matrix phase as a result of its availability, low cost, and easy processing characteristics, including forming, welding, and casting abilities. Actually, there are two main routes for AMC production depending on the aluminum state, if liquid or solid. The former is mainly used for casting alloys, and although it has been representing more than 70 pct of the AMC market,[3] it presents some drawbacks: matrix to reinforcement low wettability (mainly in the case of ceramic reinforcements), excessive interface reactions, and difficulty in obtaining a homogeneous dispersion of the reinforcing phase into the matrix as a result of differences in their densities. This scenario did not change significantly until now. In the review by Suryanarayana,[4] the many advantages in processing metals by powder metallurgy (PM) explain why this technology is preferred for producing AMC. As a solid-state process, PM avoids much of the drawbacks of the l
Data Loading...
