Optimisation of mechanical milling process for production of AA 7075/(SiC or TiB₂) composite powders

Abstract

Abstract:The present work concerns the processing of composite powders based on 7075 aluminium alloy by mechanical milling. A premixed powder (Alumix 431D, Ecka Granules, Germany) was used as the matrix material, and two different ceramic reinforcements (SiC and TiB 2 ) were chosen as reinforcements. The main objective was to evaluate the effect of the content and addition method of the process control agent as well as the content and type of reinforcement on the microstructural and morphological evolutions of the powder particles during milling process and the as milled properties of the processed materials. Results showed that regardless of the starting composition, alloying took place through three stages, in which deformation, cold welding and fracturing of powder particles were the main mechanisms involved respectively. The mechanically milled composite powders showed a fine and homogenous distribution of reinforcement particles. A higher content of reinforcement resulted in a lower crystalline size for the milled powders (,18 nm for composite powders containing 15 vol.-% ceramic particles).

Synergetic effect of milling speed and duration on particle morphology and mechanical properties of nanocrystalline Al matrix containing SiC

“…Moreover, the effect of milling time on the morphological changes, crystal size, lattice strain, density, mechanical properties of Al/SiC mixture [24], Al6061/5wt-%Si3N4 extruded bar [25], Al/AlN composite [26] and Al/SiC nanocomposite [13,27,28] were studied by different researchers. Apart from the effect of milling duration, a high milling speed of 700 rev min -1 was used by Jabbari et al [29] for various milling times to prepare AA7075/TiB2/SiC composite, where powder morphology and crystalline size were investigated. Furthermore, only a few works have been reported for Al MMCs where milling duration has been studied on Al/TiC [30], Al/Al 2 O 3 [31], Al/ CNT [32], etc., composites.…”

Synergistic strengthening of aluminum with SiC by grain refinement and dispersion hardening

“…6 Several researchers examined the impact of milling duration on morphological variations, crystal size, lattice strain, density, and the mechanical properties of SiC p /Al mixture, 32 5 wt.% Si 3 N 4 /Al6061 extruded bar, 33 AlN/Al composite, 34 and SiC Al nanocomposite. 7,8,29 In addition to milling duration, Jabbari Taleghani et al 35 applied a high milling speed of 700 rpm to prepare a TiB 2 /SiC/AA7075 composite for various milling durations to examine its effects on powder shape and crystalline size. Moreover, only a handful of studies have investigated the influence of milling duration on AMCs, for example, TiC/Al, 36 Al 2 O 3 /Al, 37 and CNT/Al.…”

Euromat 2011: powder synthesis and processing for controlled microstructure

“…Two papers deal with these problems: in critical alloys in terms of risk of oxidation1 and in the development of Fe–C base materials 2. The other papers report the use of MA to develop special materials such as aluminium base composites3 and steels with nanostructured features 4. Two contributions focus on the development and optimisation of low alloyed steels, one using the master alloy approach5 and the second employing heat treatments 6.…”