Influence of the temperature of sintering under pressure on the structure and mechanical properties of a composite material AMg2 / γ-Al2O3 nanofibres

Abstract

A nanocrystalline composite powder based on an AlMg2 alloy reinforced with 1 wt.% γ-Al 2 O 3 nanofibers was obtained in a planetary mill by mechanical synthesis. It was consolidated by sintering under pressure at a temperature of 300-450°C and a pressure of 600 MPa. The effect of the temperature of sintering under pressure on the structural-phase composition, density, hardness, and conventional yield stress of bulk composites was studied. For this, X-ray phase analysis, transmission electron microscopy, hydrostatic weighing, and mechanical testing were used. It has been found that an increase in the sintering temperature in this range leads to an increase in the relative density of compacts from 0.87 to 0.98. Based on the results of X-ray diffractometry, the sizes of coherent scattering regions corresponding to bulk composites consolidated at different temperatures are determined. It is shown that an increase in the consolidation temperature from 300 to 400°C leads to a linear increase in the size of coherent scattering regions from 109 to 495 nm, a further increase in temperature to 450°C results in a more intensive growth up to 4.2 μm. In this case, the hardness of the composite material decreases from 206 ±13 to 149 ± 3 HV 10 , which is due to the occurrence of the reduction processes and the transition of the structure from nanoscale to the micron scale. The maximum conventional yield stress for compression, 791± 58 MPa, corresponds to samples consolidated at 350°C, which is due to the overall effect of dispersion hardening by γ-Al 2 O 3 nanofibres and nanostructuring of the matrix material. An increase in temperature to 450°C neutralizes the effect of nanostructuring and leads to a reduction in the conventional yield stress for compression to 632 ± 30 MPa.

Influence of Energy-Mechanical Treatment on Structure-Mechanical Properties of Co–Cr–Mo Alloys Obtained by Spark Plasma Sintering

“…High temperature and long duration of the sintering process are disadvantages of traditional sintering methods, resulting in significant grain growth. In addition, as a rule in this case, the obtained sintered products have high porosity, which significantly reduces their mechanical properties [10,[15][16][17]. Recently, advanced technologies have been applied, such as sintering under microwave impact and spark plasma sintering (SPS) [18,19].…”