Magnetic Magnesium Alloys Based on MgZn and SmCo with Sensory Properties

Abstract

Reducing inertial masses of engineering equipment or vehicles to lower their energy requirements necessitates the use of lightweight materials possessing high static and cyclic strengths for lower densities. If, in doing this, over dimensioning of mechanical components is to be avoided then a design which is precisely matched to the loading leads to high elastic stresses and strains in the material employed. In order to avoid over loading and plastic deformation, the service loads applied to the component must be monitored. With the aid of such measured loading history data, the resulting fatigue life can be derived so that the maintenance intervals can be planned and subsequent generations of components can be optimized. If the component possesses magnetic properties, it can serve as a self-sensoring device since relevant information about the operating conditions can be collected using the magnetic material. This information can be read out and processed during the component's service by utilizing modern methods of non-destructive component testing and material characterization such as high resolution eddy current technology using harmonic analysis.According to Bozorth, the magnetic domains' length in a ferromagnetic material changes as soon as the domains' direction of magnetization is modified (magnetostriction). [1] If this is related to entire component parts made of ferromagnetic materials then the change in the entire length is the sum of all the individual domain length changes. Inverse magnetostriction (also: Villari-Effect, named after Emilio Villari, Italian physicist 1836-1904) describes the change in magnetic susceptibility, the measure of a material's magnetizability, [2] during elastic deformation. Here, the material's magnetic properties change as a function of the operating mechanical stresses because the individual domains are aligned parallel to the direction of strain. The utility of the inverse magnetostriction effect to determine the applied mechanical forces has already been demonstrated in nickel by Kaleta and Ż ebracki. [3] According to this, the voltage measured by means of a coil increases proportionally to the operating mechanical stresses within the elastic range up to the yield point. Thus, on monitoring the component using measuring technology, the quantitative data can be collected for the instantaneously operating load condition. Klever et al. [**] This research is sponsored by the German Research Foundation (DFG) within the subproject E2 ''Magnetic Magnesium Alloys'' of the Collaborative Research Center 653 ''Gentelligent Components in their Lifecycle.'' Gentelligent (genetically intelligent) components describe a new kind of machine parts which are capable of collecting, pre-processing, and storing information (e.g., temperature and forces during use of the component).In this article, manufacture of a magnetic magnesium alloy based on the known magnesium alloys AZ91 or ZEK200 together with samarium-cobalt is investigated. The objective of the investigations is to produce an Mg ...

Influence of Cobalt on the Properties of Load-Sensitive Magnesium Alloys

“…In contrast to the authors' previous publications [7], the results of the EDS measurements (Table 2) which were performed in order to determine the overall amounts of Co in the produced Mg alloys show good compliance to the nominal amounts of the ferromagnetic alloying element the Mg melts were inoculated with during the casting process. This can be credited to the use of the extruded powder rods, as they facilitate the alloying process and obviously increase alloying efficiency.…”

“…The authors already demonstrated the use of Zn as an additional alloying element in low concentrations [7,8] which improves the strength and, to some degree, the castability. In order to examine the interactions of Co and standard alloying elements like Al, Zn and Mn further investigations are currently made which focus on enhancing the mechanical properties in the as-cast state and primarily the yield strength.…”