Mechanical Properties and Nanocrystallization Behavior of Al-Ni-La Alloys

Abstract

Rapidly solidified Al 89 Ni 6 La 5 ribbons were obtained by induction melting and ejecting the melt onto a rotating Cu wheel in an Ar atmosphere. The ribbons were investigated by differential scanning calorimetry (DSC), X-ray diffractometry (XRD), transmission electron microscopy (TEM), microindentation, and nanoindentation techniques. The XRD and TEM studies revealed that the ribbon was fully amorphous; however, DSC did not show any glass transition. The alloy undergoes two stages of crystallization. The growth of fcc-Al is responsible for the first stage, and precipitation of Al 3 Ni and Al 11 La 3 is responsible for the second stage of crystallization. Microhardness of ribbons in the as-melt-spun, partially, and fully devitrified conditions was examined and subsequently correlated with evolved microstructure. Significant improvement in hardness was observed, with the progress of primary nanocrystallization, due to the effective barrier to shear band by a hard La-rich shell around the fcc-Al nanocrystals and enrichment of the remaining amorphous matrix by the solute elements. The pile up of materials in the form of semicircular shear bands was observed around all the indentations. During nanoindentation, it was observed that hardness and modulus values were initially increased and then decreased. The reasons for such observation were also discussed.

High strength nanostructured Al-based alloys through optimized processing of rapidly quenched amorphous precursors

“…The growth of the α-Al phase is constrained by crystallization of intermetallic compounds (IC) resulting in a relatively small size of α-Al (~50 nm) and the intermetallic phase (~10 nm). This limited growth of the α-Al phase together with the absence of other phase(s)/intermetallic compound(s) is consistent with observations reported previously for other Al-based metallic glasses 37,38 . The reason for this feature is attributed to solute enrichment in the matrix due to the precipitation of α-Al, even though α-Al is softer 39–41 .…”

Non-isothermal crystallization kinetics and mechanical properties of Al 86 Ni 6 Y 4.5 Co 2 La 1.5 metallic glass powder

“…This is consistent with observations reported previously for other Al-based metallic glasses [24,25]. The reason is attributed to the solute enrichment in the matrix due to the precipitation of fcc-Al, even though fcc-Al is softer [26][27][28].…”

AlNiYCo Amorphous Matrix Composites Induced by Bismuth and Lead Additions

“…The Al-based amorphous matrix composites containing a high number density of a-Al nanocrystals exhibit better mechanical properties. [14][15][16][17] Nevertheless, investigations on the Al-based amorphous matrix ex-situ and in-situ composites are scarce. [18,19] Al-Bi and Al-BiPb systems have a liquid miscibility gap owing to the positive heat of mixing.…”