## 1 Introduction
For example, in the case of gamma alloys, the first commercial flight using alloy 4822 engines in Low-Pressure Turbine Blades (LPTBs) was conducted in March 2012, but the first exploratory research into gamma alloys had begun 40 years earlier [31]. Other interesting alloys under development included in recent studies are Ni-Al alloys with memory effect and superelasticity [32] and gamma alloys [31]. A topic of special interest within the hybrid components is the joining of dissimilar materials to create the multimaterial. The main joints are mechanical, through drilling and bolts or rivets [33], and thermal, through different welding technologies. The machining of multimaterial or hybrid composites in a single operation is a challenging task because of the different characteristics of the materials resulting in different optimal machining conditions. This requires the use of compromise solutions between tool geometry and cutting parameters and frequently results in severe tool wear, increased cutting forces, poor hole quality or large burrs, worsening the difficulties in the interface between materials [18; 34; 35; 33]. For instance, the most common defects in drilling titanium in hybrid compounds are errors in hole size, roundness, position, and the existence of burrs. Titanium chips evacuation can cause scratches at the interface between materials and in the materials during the chip outlet, and the surface quality is also influenced by the number of holes made by the tool because of the effect of wear [33]. On the other hand, drilling plays a fundamental role in the assembly of parts in the aeronautical industry, and it is estimated to be used in 50% of the operations with chips removal. Therefore, it is frequently used in structural parts that require a subsequent assembly through bolts or rivets. The most frequent problems faced in the drilling process are high tool wear, poor surface quality, and out-of-tolerance diameter [36]. Likewise, a significant factor in the drilling process, analyzed in several recent works, is the influence of the tool geometry and/or its coating on the final quality of the process [7; 20; 33; 37; 38; 39]. The manufacturing of parts of responsibility for industries such as aerospace or automotive requires very strict manufacturing tolerances in terms of dimensional, geometrical, and physical-chemical properties to ensure reliable and predictable behavior in service [40]. The usual range of roughness tolerances required in the aeronautical and aerospace sector in terms of arithmetical mean roughness, \(Ra\) (\(\upmu\)m) is 0.8 \(\upmu\)m \(<Ra<\) 1.6 \(\upmu\)m [41]. In the case of rivets, they are repaired by drilling a hole to a larger diameter and using either a larger diameter river or an ACRES(r) sleeve or similar which allows the use of a bolt of the nominal design diameter [42]. The metal sheets used in the aeronautical sector are mainly obtained by rolling, and their thickness most frequently varies from very thin sheets to sheet thicknesses of more than 6 mm [43]. In addition, the advantages of residual compression stress (RCS) generated by different manufacturing processes and its effect on improving the fatigue behavior of materials have been analyzed in various papers. For example, [PERSON] et al. [44] carried out a study on the effect of shot peening on cast magnesium A8 parts. The researchers found that although the shot peening process significantly increases the surface roughness of the surfaces on which it is applied, the initiation of cracks on these surfaces is much lower than when it is not applied. The study concludes that the shot peening process increases fatigue life and delays the crack initiation, despite producing a significant increase in surface roughness. Besides, and within the study, it was achieved an increase of up to five times the working life and 30% of the fatigue resistance limit by applying shot peening to cast magnesium A8 parts.