Structural and Mechanical Evaluation of a Nanocrystalline Al–5 wt %Si Alloy Produced by Mechanical Alloying

Abstract

High energy mechanical milling followed by hot-pressing consolidation has been used to produce nanostructured Al-5 wt %Si alloy. X-ray diffraction (XRD), scanning electron microscopy equipped with energy dispersive X-ray detector (SEM-EDX), Vickers hardness, and compression measurements were used to examine the effect of milling duration on microstructure and mechanical properties of the nanostructured consolidated alloys. Crystallite sizes and lattice strains were determined by X-ray peak broadening analysis using the Williamson-Hall (W-H) method. Increasing the milling time reduced the crystallite size, and the minimum crystallite size of about 33 nm was achieved for both consolidated and powdered samples after 50 h of milling. Based on the SEM-EDX observations, the best distribution of silicon into Al matrix was obtained after 20 h of milling and remained unchanged afterwards. Hardness of both consolidated and powder samples increased with milling time, which can be attributed to the reduction of crystallite size and the better distribution of silicon in the aluminum matrix. Similarly, increased milling time increased the yield and compressive strengths of consolidated samples.

Microstructure and Mechanical Properties of AA7075 Aluminum Alloy Fabricated by Spark Plasma Sintering (SPS)

“…Typical FESEM images of the AA7075 powder at medium ( Figure 2 a) and higher ( Figure 2 b) magnifications show rounded particles with a spherical or more elongated shape and a large size distribution, consistent with the gas atomization practices employed for its production [ 33 ]. For the AA7075-M powder, the particles have taken the shape of micrometric flakes about 1 µm thick and with lateral dimensions in the range 10–100 µm, which is a typical morphology for milled soft metals for a short time (≤ 5 h), as reported in previous works [ 34 , 35 ]. In particular, Razavi-Tousi and Szpunar [ 35 ] found that using various milling conditions, aluminum particles always tend to form disc-shaped particles for short milling times due to cold welding.…”

“…Table 2 also shows the estimated value of the density of dislocations for each sample, which was obtained using Equation (7). Comparing values for AA7075 and AA7075M highlights that milling considerably increases the density of dislocations [34,40]. Moreover, sintering reduces the density of dislocations, as it increases the size of the crystallite and decreases the strain of the lattice.…”

Wear Dry Behavior of the Al-6061-Al2O3 Composite Synthesized by Mechanical Alloying

“…The mechanical alloying can be used to produce alloys and compounds that are difficult or impossible to obtain by conventional melting as casting techniques [17][18][19][20]. The mechanical alloyed technique consists of repeated welding, fracturing, and rewelding of powder particles, leading to particle size variations and changes in the powder particle shape [16].…”

Microstructural Evolution, Thermal Stability and Microhardness of the Nb–Ti–Si-Based Alloy during Mechanical Alloying

“…The mechanical alloying (MA) process, a typical high-energy ball milling operation involving repeated fracturing and cold welding of the powder particles [13][14][15], is a common method to prepare powder blends, and has a significant influence on the subsequent consolidation of the powder mixtures [16,17]. We have recently investigated the evolutions of morphology and phase constituents of Nb-Ti-Si-based alloy powder blends (with the nominal composition of Nb-20Ti-15Si-5Cr-3Hf-3Al (at %)) during ball milling at low and moderate milling speeds [18].…”