The Glassy Structure Formation and Phase Evolution in Mechanically Alloyed and Spark Plasma-Sintered Al-TM-RE Alloys

Abstract

5 alloy powders via mechanical alloying performed at 300 revolution per minute with ball-to-powder ratio of 15:1 and subsequently the devitrification tendency of 300°C and 500°C spark plasma-sintered bulk amorphous alloys. Mechanically alloyed .5 powders yielded nearly fully amorphous structure after 140, 170 and 200 h, respectively. The requirement of prolonged milling was attributed to the soft and ductile nature of aluminum with high stacking fault energy. Amorphous powders were consolidated via spark plasma sintering at 300 and 500°C by applying a constant pressure of 500 MPa. X-ray diffraction was performed on the 300-and 500°Csintered samples. XRD patterns of the 300°C-sintered alloys exhibited very-low-intensity nanocrystalline FCC-Al peak overlaying an amorphous hump evincing retention of a large amount of the amorphous phase. Enhanced devitrification tendency was reported in the 500°C-sintered alloys; however, a major difference in the devitrification tendency of the 500°C-sintered Al 86 Ni 8 Y 6 , Al 86 Ni 6 Y 6 Co 2 and Al 86 Ni 6 Y 4.5 Co 2 La 1.5 alloys was that the quinary alloy exhibited higher tendency of devitrification, which was also corroborated by performing HRTEM and analytical TEM experiment. This could be attributed to the higher probability of coupling of atoms by short-range atomic shuffling during spark plasma sintering. Vickers hardness, and relative density estimated via ArchimedesÕ principle, varied depending on the degree of free volume annihilation and crystallization during sintering.

Advances in Synthesis and Characterization of Aluminum‐Based Amorphous Alloys: A Review

“…Chemical composition of amorphous powder particles also influence the sintering behavior. [ 182 ] The interesting outcome of the work done by the present authors suggests that higher number of components in different Al–TM–RE alloy systems supplemented the devitrification phenomena. It was confirmed from the comparative study of XRD patterns of 300 and 500 °C sintered Al 86 Ni 8 Y 6 , Al 86 Ni 6 Y 6 Co 2 , and Al 86 Ni 6 Y 4.5 Co 2 La 1.5 samples.…”

“…It was confirmed from the comparative study of XRD patterns of 300 and 500 °C sintered Al 86 Ni 8 Y 6 , Al 86 Ni 6 Y 6 Co 2 , and Al 86 Ni 6 Y 4.5 Co 2 La 1.5 samples. [182] The XRD patterns of the 300 °C sintered Al 86 Ni 8 Y 6 , The configurational entropy (S config ) is also increased by the presence of higher number of components in the composition. Consequently, the probability of coupling of atoms which follows the Stokes-Einstein equation also increases and leads to more devitrification.…”

“…It was confirmed from the comparative study of XRD patterns of 300 and 500 °C sintered Al 86 Ni 8 Y 6 , Al 86 Ni 6 Y 6 Co 2 , and Al 86 Ni 6 Y 4.5 Co 2 La 1.5 samples. [ 182 ] The XRD patterns of the 300 °C sintered Al 86 Ni 8 Y 6 , Al 86 Ni 6 Y 6 Co 2 , and Al 86 Ni 6 Y 4.5 Co 2 La 1.5 samples are shown in Figure 32. XRD pattern of Al 86 Ni 8 Y 6 alloy system reveals completely broad hump without any detectable crystalline peak.…”

“…Figure 31. a) TEM image revealing crystalline rich and deficit regions of Al 86 Ni 6 Y 4.5 Co 2 La 1.5 sample sintered at 500 °C; SAED patterns from b) crystalline-rich region revealing bright dots and c) amorphous rich region revealing diffused pattern with few dots. Reproduced under the terms of the CC-BY 4.0 [182]. Copyright 2019, Springer Nature.…”

“…XRD patterns of the samples consolidated at 300 °C revealing amorphous hump superimposed with FCC-Al nanocrystalline peaks. Reproduced under the terms of the CC-BY 4.0 [182]. Copyright 2019, Springer Nature.…”