• PDF / 1,246,686 Bytes
• 13 Pages / 584.957 x 782.986 pts Page_size
• 96 Downloads / 191 Views

DOWNLOAD

REPORT

---

this study, Aluminum-based nanocomposites with hybrid reinforcements were successfully prepared by mechanical alloying, followed by consolidation using selective laser melting (SLM). The evolution of particle morphology and microstructural features of the milled powders at various milling times was studied. The results indicated that the milled powder particles experienced a coarsening stage at the early 5 h milling and followed by a continuous refinement during 5–20 h milling. After 20 h of milling, the original coarse needle-like Al3.21Si0.47 evolved into nanometer/submicrometer-sized spherical Al3.21Si0.47. Meanwhile, both fine Al3.21Si0.47 and ex-situ nanoscale TiN particles distributed uniformly within the Al matrix. By SLM processing of the 20-h powder, a near fully dense part with a uniform microstructure consisting of circularly dispersed and submicrometer-sized reinforcement particles embedded in a-Al matrix was obtained. The Vickers hardness and coefficient of friction of the SLM-processed part reached 178 HV0.1 and 0.38, respectively.

I. INTRODUCTION

Contributing editor: Yang-T. Cheng a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2015.267

efficient method to avoid agglomeration of nanoparticles and improve the distribution of nanoparticles throughout metal matrix.4–6 During MA processing, powder particles undergo a series of evolutions of morphology, size, and microstructure by means of repeated deformation/welding/ fracture mechanisms. These evolutions involve mass transfer between different components, therefore accelerating the homogeneously distributing process.7 The nanocomposites with different matrixes have been successfully synthesized through MA. For instance, Zhou et al. successfully achieved the nanostructured Cu–5 wt%Al2O3 nanocomposites powder by high-energy mechanical milling and simultaneously studied the grain growth of nanocrystalline Cu matrix during annealing. It had been found that the microstructure of the nanocrystalline Cu matrix exhibits a good thermal stability, due to the dramatic drag effects of finely distributed Al2O3 nanoparticles and Al31/O2
clusters on the grain boundary motion.8 El-Eskandarany used high-energy ball milling to achieve SiC reinforced Al-based nanocomposites. It was further found that the increasing volume fractions of the SiC reinforcement led to an increase of the density, hardness, and elasticity modulus of the composite samples.9 Also, the nanocomposites reinforced with nanometer-sized TiC dispersed uniformly throughout the W matrix were produced by Zhang and Gu through MA and the amorphization of W constitute gradually occurred with the milling time increasing.10

2816

Ó Materials Research Society 2015

Metal matrix nanocomposites (MMNCs) are developed from metal matrix composites (MMCs), the main characteristic of which is that at least one of phases shows dimensions in the nanometer range (1 nm 5 10
9 m). Obviously, there are a large number of interfaces between the matrix and reinforcements by the additi