Yield strength of the monocrystalline intermetallic compound MgZn2

Abstract

Dynamical compression tests in the temperature range of 300 to 500 "C are carried out and discussed for single crystals of the intermetallic compound MgZn,. The influence of temperature and chemical composition of the crystals withi:i the range of homogeneity on the plastic behaviour is investigated. The yield drop observed is discussed in terms of a dislocation model. A dislocation multiplication rate leading to e burn is postulated. Stress-strain curves are simulated on the basis of the Orowan equation and compared with a representative experimental curve. From microscopic surface pictures, taken during the deformation, the growth velocity of slip steps is estimated.Dynamische Kompressionsversuche werden im Temperaturbereich 300 bis 500 "C an Einkristallen der intermetallischen Verbindung MgZn, durchgefuhrt und diskutiert. Parameter der Spannungs-Dehnungs-Kurven sind die Temperatur und die chemische Zusammensetzung der Kristalle innerhalb des Homogenitstsbereiches. Der beobachtete Streckgrenzeneffekt wird im Rahmen eines Versetzungsmodells der plastischen Verformung diskutiert. Es wird eine Versetzungsvervielfachung gemaBum postuliert. Auf der Grundlage der Orowanschen Beziehung rechnerisch simulierte Spannungs-Dehnungs-Kurven werden mit einer reprasentativen experimentellen Kurve verglichen. Aus Oberflachenphotographien, wahrend der Verformung aufgenommen, wird die Wachstumsgeschwindigkeit von Gleitstufen ermittelt.

Composition dependence of hardness and elastic modulus of the cubic and hexagonal NbCo2Laves phase polytypes studied by nanoindentation

“…Softening of Laves phases with deviation from the stoichiometric composition was reported by several authors [5,8,22], but the underlying mechanism is not clear yet. An example is the MgZn 2 Laves phase.…”

“…An example is the MgZn 2 Laves phase. As the composition deviates from the stoichiometric composition, a decrease in hardness and yield strength was observed accompanied by a reduction in the initial dislocation density [22,23]. The softening effect is attributed to the decrease in the initial dislocation density at off-stoichiometric compositions [23].…”

Factors affecting the room-temperature mechanical properties of TiCr2-base Laves phase alloys

“…Deviations from stoi chiometry in the intermetallic NiAl result in increases in hardness and strength, and Ni vacancies were found to be more potent strengtheners per unit addition than Ni anti-site defects [3]. The deformation properties of the Laves phase MgZn 2 have been reported to be strongly dependent on the compositions within the range of homogeneity [4]. Due to the topological close-packing of atoms in Laves phases, defects associated with offstoichiometric compositions may modify the atomic motions involved in the synchroshear deformation mechanism [1].…”

Determination of the Rate Dependence of Damage Formation in Metallic‐Intermetallic Mg–Al–Ca Composites at Elevated Temperature using Panoramic Image Analysis

“…[1][2][3] In contrast, the presence of intermetallics naturally leads to decreased tensile elongation, as the present intermetallic phases such as Mg 17 Al 12 or Laves phases such as CaAl 2 (C15), Ca(Mg,Al) 2 (C36), and CaMg 2 (C14) are hard and brittle, particularly below approximately two-thirds of their melting temperature. [4][5][6][7][8][9][10][11] As both low and elevated temperature regimes, that is room temperature and temperatures around and above 150 °C, are of interest in application, the underlying deformation and damage mechanisms and their thermal activation need to be understood. In particular, the competition between brittle fracture and plasticity, enabled by dislocation glide or diffusional processes, may be expected to determine any temperaturedependent macroscopic transitions in mechanical behavior.…”