# Measurement of Elastic Properties of Brittle Materials by Ultrasonic and Indentation Methods
## 1 Introduction
[5], e.g., Gruneisen parameter, thermal conductivity, thermal relaxation time, thermal energy density, specific heat, granular size, Debye average velocity, and concentration etc. It is also a certain trace imprinted on material that may be used for characterization. Instrumented indentation [10] is a technique investigated for determining both the elastic and plastic properties of the materials. The nanoindentation method [11] gained popularity with the development of advanced instruments that can record micro load and displacement with high precision. If the indentation is taken at a nanoscale level it can provide accurate measurements of the continuous variation of indentation load down to micro Newton, as a function of the indentation depth down to nanometer. [PERSON] et al. [12] used standardized experimental procedure and analytic models (depending on the indenter shape identified by [PERSON] et al. [13]) the load-displacement data can be used to determine elastic moduli, hardness and other mechanical properties including residual stresses. Metallic glasses can be described as metals or metal alloys without crystalline structure. Metallic glasses exhibit unique characteristics, i.e., the absence of translational periodicity and compositional homogeneity. They are usually prepared by rapid solidification during liquid phase. According to [PERSON] [14], the crystallization can be avoided when the cooling rate is high enough, so that the atoms can be frozen in their liquid configuration as the solidification occurs. Unlike conventional metallic materials, metallic glasses do not exist in long-range atomic order, from which endowed some unique and interesting properties, e.g., high strength, elastic limit, toughness, good corrosion resistance, wear resistance and soft magnetic properties [15]. In industry, bulk metallic glasses (BMG) have been used as material for golf club heads, mobile phone casing, scalpels, tennis rackets, high-frequency power coils, and high torque geared motor parts [16; 17; 18; 19]. It is very interesting to investigate how the special inherent structure impacts the acoustic properties of BMG. However, very few studies associated with the acoustic properties were made and most of the mechanical properties were performed by other modalities, most frequently by the tensile tests. The turbine disk and blades of many small gas turbines, especially small aircrafts, turbo-fan missiles and vehicular engines, are usually cast into a single piece, generally known as integral wheels. There is a considerable variance of loading conditions from blade to disk, i.e., lower temperature and high stress at the hub versus high temperature and low stress at the tip. The materials used to construct the integral wheel must fit in the requirement of both blade and disk. These materials, therefore, must have a very high tensile strength at operating temperature of the hub to protect the parts from bursting, and high creep strength under the blade operating condition. CM247 LC is a class of cast nickel-based superalloys with low carbon content, which was investigated by [PERSON] et al. [20]. [PERSON] [21] discovered that it is a modified superalloy based on the chemical composition of Mar-M247, specifically designed for producing directionally solidified (DS) turbine blades. The reason for the designated application is that the CM247 LC superalloy is exceptionally castable to form an equiaxed grain structure if the casting parameters are well controlled. Therefore, high strength and superior creep resistance can be achieved. The control of the grain size (finer grain is preferred) is crucial for maintaining the required standard of both physical and mechanical properties [22; 23]. In spite of the unique granular structure of the above stated materials, rather little research has touched upon the relationship between the acoustic properties and elastic moduli.