## 1 Introduction  
The first ever produced dispersion-strengthened alloys with distribution of uniform dispersoid were synthesized by the powder metallurgy method commonly known as mechanochemical alloying [1]. It is further used as a powerful non-equilibrium processing method that can be deployed to synthesize a variety of meta-stable structured materials [2]. Categorically, the milling of particles is classified as (i) mechanical milling where the similar nature of elements or compounds can be milled, and (ii) mechanical alloying where dissimilar constituents can be milled with transfer or sharing of material species [2; 3; 4]. The advent of ball milling thus supported the production of nanostructure materials that are meta-stable when compared to their pristine counterparts. The grain size refinement is a controllable property based on the mechanochemical agitation, features, and properties of the constituent powders involved in the milling technique and, finally, the amounts of defects and/or dislocations introduced based on the plastic deformation during the thermal recovery processes [2]. In a typical high energy mechanochemical milling process, the reactive ingredients are added with the required balls and the media in a closed container. Then, after specific milling experiment, very fine particulates of the product are obtained, which are often of micrometric size; however, the components that are welded together are nano-sized,for industrial and research quality. The \"media\" refers to fluids (for example, liquid media such as solvents, DI, surfactants, or dispersants, and gaseous media such as air, argon, nitrogen, and reactive atmospheres, namely, hydrogen). The root cause of nanostructural formation could be due to the two concurrent processes, particle fracturing and agglomeration/aggregation (or cold welding in the case of mechanical alloying) that occur at different rates. Additionally, the milled product exhibits a large number of defect accumulation sites. Compared to many other synthesis techniques, solid state milling has dual advantages, for example, this process can not only produce ultra-fine nanoparticles with definite stoichiometric ratios, but also enable those products with high yield, greater densification, and homogeneity. However, a segregation phenomenon like presence of reagents residue that is unavoidable during the milling of diverse materials [3]. For the development of new and advanced materials, with appropriate stress-strain characteristics, the ball milling or rod milling techniques have been considered potential and powerful tools. The mechanical alloying is a unique technique that can be performed at ambient conditions and with different types of mills, such as high (or low) energy, centrifugal type, attritor type, vibratory type, and tumbling type. In the vibratory type of ball mill, grinding of the materials can be performed with vibratory motions with high frequencies and low amplitudes. The ball's velocity in the vibratory milling apparatus is much greater than that of planetary ball mill system; therefore, less time may be needed for the particle size reduction in the vibratory ball mills. Here, the similar parameters need to be considered at time of milling process, i.e., milling speed, milling time, grinding medium, atmosphere, etc. Another type of milling apparatus involving planetary motions of the sample vials containing the materials to be grinded are called planetary ball mills. In this planetary milling method, an equal magnitude, as well as an opposite direction of forces with the containers and the underneath support disks, often produces both friction (due to balls rolling on the walls) and severe impact (due to the balls hits each other or with the milled powder). In a single event of planetary ball mill, at least few hundred grams of the initial powders can be milled with high consistency and uniformity.