Microstructure and mechanical properties of slowly cooled Cu_47.5Zr_47.5Al₅

Abstract

Cu 47.5 Zr 47.5 Al 5 was prepared by arc melting and solidified in situ by suction casting into 2-5-mm-diameter rods under various cooling rates (200-2000 K/s). The microstructure was investigated along the length of the rods by electron microscopy, differential scanning calorimetry and mechanical properties were investigated under compression. The microstructure of differently prepared specimens consists of macroscopic spherical shape chemically inhomogeneous regions together with a low volume fraction of randomly distributed CuZr B2 phase embedded in a 2-7 nm size clustered "glassy-martensite" matrix. The as-cast specimens show high yield strength (1721 MPa), pronounced work-hardening behavior up to 2116 MPa and large fracture strain up to 12.1-15.1%. The fracture strain decreases with increasing casting diameter. The presence of chemical inhomogenities and nanoscale "glassy-martensite" features are beneficial for improving the inherent ductility of the metallic glass.

Deformation-induced martensitic transformation in Cu–Zr–(Al,Ti) bulk metallic glass composites

“…It is important to note here that the B2 CuZr phase can only be obtained from the glassy state by proper adjustment of the cooling rate. Annealing treatments of glassy alloys lead to the formation of metastable phases or the precipitation of the equilibrium phases, depending on the composition [20].To the best of the authors' knowledge only the formation of martensite in Cu-Zr-based partially glassy alloys upon quenching has been reported so far [19,[21][22][23][24]. This is due to the stresses in the material that occur during the solidification process that usually trigger martensite formation.…”

“…To the best of the authors' knowledge only the formation of martensite in Cu-Zr-based partially glassy alloys upon quenching has been reported so far [19,[21][22][23][24]. This is due to the stresses in the material that occur during the solidification process that usually trigger martensite formation.…”

Microstructure and Compressive Properties of <I>In-Situ</I> Martensite CuZr Phase Reinforced ZrCuNiAl Metallic Glass Matrix Composite

“…The structure, size, and distribution of the reinforcement are strongly influenced by the compositions and the solidification conditions. [12][13][14] These composites show obvious plastic deformation and work-hardening behavior under roomtemperature compression. The enhanced mechanical properties are attributed to the stress-induced martensite transformation from a cubic primitive B2 CuZr austenite phase to a monoclinic B19 0 CuZr martensite phase.…”

Effect of Tempering on Microstructure and Mechanical Properties in a Multiphase ZrCuAlNiO Alloy

“…7,8) The formation of martensite phases has been observed in a number of Zr-Cu(Ni) based multi-component alloys during rapid cooling or straining. [9][10][11][12][13][14][15] Previous studies have indicated that the ZrCu phase should be a metastable phase and could be saved by a rapid cooling. If the cooling rate is not large enough, the ZrCu phase with a B2 structure could transform into two martensite phases with the monoclinic symmetry.…”

“…12,13) The ZrCu martensites and ZrCu (B2) phases could be used as reinforcement in the Zr-Cu(Ni) based alloys to improve the strength and toughness of the materials. [15][16][17][18][19][20][21] In addition, the Zr-Cu(Ni) system exhibits particular promise for developing precipitation-strengthened multiphase alloys. However, a problem is the incomplete knowledge of the stability of various phases in Zr-Cu(Ni) system alloy at high temperatures.…”