Influence of the Oxide and Ethanol Surface Layer on Phase Transformation of Al-Based Nanocomposite Powders under High-Energy Milling.

Dora Janovszky

doi:10.3390/ma12081305

Abstract

Pure Al particles reinforced with amorphous-nanocrystalline Cu36Zr48Ag8Al8 particles composite powders were prepared by high-energy milling without and with ethanol. The mechanical milling procedures were compared so that in the case of dry milling the particle size increased owing to cold welding, but the crystallite size decreased below 113 nm. The amorphous phase disappeared and was not developed until 30 h of milling time. Using ethanol as a process control agent, the particle size did not increase, while the amorphous fraction increased to 15 wt.%. Ethanol decomposed to carbon dioxide, water, and ethane. Its addition was necessary to increase the amount of the amorphous structure.

Highlights

The demand for Al-based metal matrix composites (AMMCs) will continue increasing at unstoppable rates due to development in the automotive and construction industry
The Rietveld refinement shows that the unit cell of the CuZr phase is a= 0.4541 nm, i.e., the crystal structure of this phase is distorted
This phase is hereinafter referred to as the CuZr(Ag,Al) phase based on the X-ray diffraction (XRD) results

Summary

Introduction

The demand for Al-based metal matrix composites (AMMCs) will continue increasing at unstoppable rates due to development in the automotive and construction industry. Improvement in the strength of aluminum alloys can be achieved by uniformly distributed hard materials such as oxides [1,2], borides [3], carbides [4], graphene [5,6] or carbon nanotubes [7,8]. The introduction of metallic particles, amorphous-nanocrystalline alloy, can solve these problems owing to their high strength, large elastic limit, high corrosion resistance, and good wettability by the metal matrix [10,11]. The powder metallurgical route can be successfully employed to fabricate an amorphous/nanocrystalline composite powders in which the reinforcing particles are uniformly distributed in the Al- matrix. A process control agent (PCA) such as stearic acid, benzene, methanol, or ethanol is added to the powder mixture during milling to reduce the effect of cold welding between powder particles [16,17,18]. The PCA adsorbs on the surface of the powder particles and minimizes cold welding between powder particles and thereby inhibits agglomeration [19,20]

Methods

Results

Conclusion