Microstructure and Mechanical Properties of Nanocrystalline Al-Zn-Mg-Cu Alloy Prepared by Mechanical Alloying and Spark Plasma Sintering

Abstract

In this study, Al, Zn, Mg and Cu elemental metal powders were chosen as the raw powders. The nanocrystalline Al-7Zn-2.5Mg-2.5Cu bulk alloy was prepared by mechanical alloying and spark plasma sintering. The effect of milling time on the morphology and crystal structure was investigated, as well as the microstructure and mechanical properties of the sintered samples. The results show that Zn, Mg and Cu alloy elements gradually dissolved in α-Al with the extension of ball milling time. The morphology of the ball-milled Al powder exhibited flaking, crushing and welding. When the ball milling time was 30 h, the powder particle size was 2–5 μm. The α-Al grain size was 23.2 nm. The lattice distortion was 0.156% causing by the solid solution of the metal atoms. The grain size of ball-milled powder grew during the spark plasma sintering process. The grain size of α-Al increased from 23.2 nm in the powder to 53.5 nm in the sintered sample during the sintering process after 30 h of ball milling. At the same time, the bulk alloy precipitated micron-sized Al2Cu and nano-sized MgZn2 in the α-Al crystal. With the extension of ball milling time, the compression strength, yield strength and Vickers hardness of spark plasma sintering (SPS) samples increased, while the engineering strain decreased. The compression strength, engineering strain and Vickers hardness of sintered samples prepared by 30 h milled powder were ~908 MPa, ~8.1% and ~235 HV, respectively. The high strength of the nanocrystalline Al-7Zn-2.5Mg-2.5Cu bulk alloy was attributed to fine-grained strengthening, dislocation strengthening and Orowan strengthening due to the precipitated second phase particles.

On the Formation of AlNiCo Nano-Quasicrystalline Phase during Mechanical Alloying through Electroless Ni-P Plating of Starting Particles

“…Additionally, with the existence of QC peaks, the intensity of the elemental peaks diminished, specifically at the angles of 2θ = 41.88 and 47.45°. Using the well-known Williamson-Hall’s equation [10,11], the crystallite/quasicrystal size of the coated powders after 360 min of BM was calculated to be 17.7 nm, while the corresponding crystallite size was 55.5 nm for the raw powder system. This variation can be originated from the formation of a much harder QC phase in the coated powder system with increasing the milling time, which causes acceleration of reduction in crystallite/quasicrystal size.…”

Effect of mechanical milling on microstructure evolution and mechanical properties of Al–Zn–Mg–Cu–Si alloy fabricated via spark plasma sintering

“…14,15 Recent studies on 7xxx PM alloys have shown that HEBM results in the dissolution of precipitates present in powders and a more homogeneous distribution of solutes. 16,17 The oxide and nitride surface layers of the powder can be introduced into the matrix during milling, which plays an important role in maintaining the fine grain structure and dispersion strengthening in sintered and heat-treated alloys. 18 Al alloy powders have also been used in additive manufacturing (AM) processes for applications in the aerospace, defence, and automotive industries.…”

Producing Metal Powder from Machining Chips Using Ball Milling Process: A Review

“…Mechanical alloying as a method of solid-state particle processing that involves m Among various metal matrix composites (MMCs), the 7xxx series, which consists of minor alloying elements such as Zn, Mg, and Cu, have garnered more attention compared to conventional metal-based alloys for use as matrix materials. This is due to their high specific mechanical properties, lightweight nature, and easy availability [49,50]. Moreover, copper holds significant importance in the manufacturing industry as it is extensively utilized for the production of a wide variety of products.…”