## 4 Discussion and Future Trend  
Following the background discussed in the literature review, the justifications for the current state-of-the-art proposal have been developed based on the research potential noticed after classifying the papers. The purpose of these prospects is to direct the research's actions so that they are correctly initiated. Our findings show that field is still in its infancy. The research maturity of the papers included in the literature review suggests that cellular lattice structures in additive manufacturing are still an emerging field. The yearly distribution of related publications supports this finding, showing that research activity from 2019 increased at much higher rates than the general position in the same field. In the first 5 years, research is greatly focused on only Titanium alloys, and now for the past 3 years Inconel 625/718, stainless steel, Al alloys, and Maraging steel are emerging for industrial applications. However, Titanium alloys are still increasingly used as Porous lattice structures in biomedical implants, and aerospace applications due to their lightweight, cheaper cost, and strength-weight ratio [89]. Powder bed fusion is employed with laser and electron beam also increased two times than normal use by its applications for manufacturing small components. DED technology is preferred by the manufacturer  
Figure 31: Comparison of all experimental data for ER70S-6 WAAM specimens under different fatigue load types. Reprinted with permission from ref. [73]. 2022, Elsevier. Figure 32: Comparison between CDM-based predicted results and experimental results. Reprinted with permission from ref. [88]. 2021, Elsevier. for larger components and for repairing worn-out parts. The numerical method by FE-simulations remains constant but the utility of open-source software increases steadily over the commercial software of its cost. The validation of experimental papers with numerical analysis has grown over only the experimental investigation method. According to the systematic study, data of SLM, EBM, and DED, Ti-6 Al-4V shows that unpolished specimens performed poorly with no measurable effect of any postprocessing, while the fatigue strength was increased by a factor of 2-3 for the specimens tested with a polished surface. In polished specimens, heat treatment (without HIPing) did not show any significant improvement in fatigue performance as compared to non-heat-treated specimens [90]. After identifying the critical locations and stresses of a part using FEA, the performance of AM components may be enhanced by fine-tuning the processing parameters and design parameters during production. This technology is very cost-effective and time-saving for the AM process [91]. The optimization methodology proposed was able to find an efficient geometry, and fulfill the design requirements [92]. The optimization was proved to be efficient by optimizing the volume and the mass of the component was 12.53% of the initial domain. The stiffness-to-mass ratio was almost six times higher than the initial value. The residual stresses resulting from the AM process have a substantial influence on fatigue. Therefore, it must be considered during the design phase of components vulnerable to cyclic stresses [93]. To reduce the residual stress upon processing, the build platform was heated to 200 \({}^{\circ}\)C. Moreover, before machining the cylinders were stress-relief, and heat-treated at 800 \({}^{\circ}\)C for 2 h., under a vacuum atmosphere [94]. By examining SEM imaging that shows a sub-surface fusion fault [95]. It is between many-particle boundaries and cracks to the surface. Indeed, unmelted powder forms between two-particle boundaries. Material anomalies indicate the prevalent porosity type and process-inherent flaws in fatigue specimens. It has been investigated that experimental fatigue results were estimated according to a probabilistic model. The resulting S-N curves were approximately the same with the scatter bands being nearly coincident [96].