Effect of Processing Parameters on the Microstructure of Mechanically Alloyed Nanostructured Al-Mn Alloys

The grain boundary, solid solution, and precipitation strengthening mechanisms are important for controlling the mechanical properties of Al-based alloys. Due to severe plastic deformation, mechanical alloying refines grain structure to a nanoscale level which leads to a strong increase in solute content and the related strengthening effect of solute atoms and secondary-phase precipitates. This study analyzed the elemental Mn and Al6Mn phase dissolution in Al during high-energy ball milling. For this purpose, XRD data, microstructure, and hardness evolutions were compared for two Al—5.2 at% Mn alloys prepared by mechanical alloying using elemental Al and Mn powders and a pre-melted master alloy. In the two-phase master alloy, containing the Al solid solution and the Al6Mn phase, the strain accumulation, grain refinement, solid solution supersaturation, and milling-induced hardening effects were facilitated. Both elemental Mn and intermetallic compound were dissolved during mechanical alloying, and the maximum solute content was near 3.1 at% Mn. A fine crystalline size of ~25 nm and the maximum Mn solute content were observed after milling of elemental powders and the master alloy for 60 h and 20 h, respectively. The microhardness of ~3 GPa corresponded to a ~3.1% solute Mn content, and the microhardness increased to ~5 GPa after long–term milling due to precipitation strengthening effect of the secondary Al6Mn phase in the master alloy.

Section: Dissolution and Precipitation Effectssupporting

confidence: 65%

Effect of Mechanical Alloying on the Dissolution of the Elemental Mn and Al-Mn Compound in Aluminum

Yakovtseva,

Emelina,

Mochugovskiy

et al. 2023

“…The main processes observed during the mechanical alloying of the studied Al-7.7Mn-4.9Zr-3.2Cu alloy are the grain refinement and dissolution of the alloying elements with further precipitation of the secondary Al6Mn phase after long-term milling. These processes were the same as those for the binary Al-10Mn alloy [69,70] and ternary Al-Mn-Cu alloys, with similar ~8%Mn and ~3.5%Cu [74] and with higher element contents of ~15.3%Mn and ~6.2%Cu [98]. Zirconium was completely dissolved in Al, but the precipitation of the Al3Zr phase was not detected during the mechanical alloying of the studied alloy.…”

Section: Effect Of Mechanical Alloyingsupporting

confidence: 62%

“…Large concentrations of the lattice defects are conductive to high diffusivity, which increases the solubility of the alloying elements. The abnormally supersaturated solid solutions are formed during MA of Al-Mg [61,62], Al-V [63,64], Al-Fe [65,66], Al-Mn [67][68][69][70], and Al-Zr [71][72][73] alloys. The solubility of Zr and Mn is increased to ~8 at% [71] and ~3.1-3.5 at% [67,74], respectively.…”

Section: Introductionmentioning

confidence: 99%

The Microstructure and Properties of Al–Mn–Cu–Zr Alloy after High-Energy Ball Milling and Hot-Press Sintering

Yakovtseva,

Mochugovskiy,

Prosviryakov

et al. 2024

In the present research an Al–7.7%Mn–4.9%Zr–3.2%Cu (wt%) alloy was processed by mechanical alloying (MA) followed by hot press sintering. The microstructure, phase composition, and mechanical properties of the MA granules and sintered samples were investigated. The dissolution of Mn, Zr, and Cu with further precipitation of the Al6Mn phase were observed during high-energy ball milling. In the alloy processed without stearic acid after milling for ~10 h, an Al-based solid solution with ~4.9 wt%Zr, ~3.2 wt%Cu and a ~5 wt%Mn with a grain size of ~16 nm and a microhardness of ~530 HV were observed. The addition of stearic acid facilitated Mn dissolution and precipitation of the Al6Mn phase during milling but led to the formation of the ZrH2 phase that decreased the Zr solute and the microhardness. Precipitation of the Al6Mn, L12–Al3Zr, and Al2Cu phases during annealing and sintering of the MA granules in the temperate range of 350–375 °C was observed, and an additional Al20Cu2Mn3 phase was precipitated at 400–450 °C. Hot-press sintering at 450 °C provided a low fraction of cavities of ~1.5%, the yield strength of 1100 MPa, ultimate compressive strength of 1200 MPa, strain at fracture of 0.5% at room temperature, the yield strength of 380 MPa, ultimate compressive strength of 440 MPa, and strain at fracture of 3.5% at 350 °C. The microstructural evolution during high-temperature deformation on the sample surface was studied and the differences in deformation behavior for the alloys sintered at different temperatures were discussed.

“…An anomalous increase in solid solubility is observed after mechanical alloying due to severe plastic deformation and the resulting high density of crystalline defects, e.g., vacancies, dislocations, and grain boundaries [29,[32][33][34][35][36][37][38][39][40]. The solute content of the low-soluble elements in aluminum, Nb [41,42], Co [43], V [44,45], Zr [46,47], and Ti [26], increases, and a strong extension of the Mn [4,48] and Mg [49] solubility is observed. For the same reasons [50][51][52][53][54][55][56][57][58], solute content increased significantly after high-pressure torsion [59][60][61].…”

Section: Introductionmentioning

confidence: 99%

Influence of Pre-Milling on the Mn Solid Solubility in the Al-Mn-Cu Alloy during Mechanical Alloying

Yakovtseva

Emelina

Mochugovskiy

et al. 2023

Increasing the strength of Al-based alloys is an important issue of physical metallurgy and industrial processing. Severe plastic deformation and related extension of solid solubility during mechanical alloying provide an opportunity for significant strengthening due to grain refinement, solid solution, and precipitation strengthening mechanisms. During mechanical alloying, an anomalous increase in the solid-state solubility of alloying elements occurs. The present study focuses on the investigation of the pre-milling treatment to the microstructure, phase composition, and solubility in Al-7.7 Mn-3.5 Cu (wt%) alloy processed by a high-energy ball milling of Al-14.3 Mn-6.5 Cu (wt%) master alloy diluted with Al powder. During milling, the mean granular size decreased to ~5 µm, and a strong grain refinement occurred. According to our TEM and XRD data, ball milling provided a mean grain size of 13–14 nm and a microhardness of 490–540 HV. The lattice parameter of the Al-based solid solution decreased with an increase in the milling time to 7.5–10 h, which suggested the dissolution of the alloying elements, and the lattice parameter increased at a higher milling time of 12.5–40 h, which suggested the decomposition of the solid solution. The XRD data revealed the dissolution of the Al6Mn and Al20Cu2Mn3 solidification-originated phases with a further precipitation of the Al6Mn dispersoids. Pre-milling of the master alloy entailed a significant decrease in the minimal lattice parameter value from 0.4029 nm to 0.4023 nm due to an increase in the Mn solute content from 6.2 wt% (3.3 at%) to 7.5 wt % (4.0 at%) in the studied alloy during high-energy ball milling.