## 4 PBF-LB/M Process
### Design
#### 4.1.1 Novel Lightweight Compositions  
To enhance sustainability and efficiency, the design of novel high-performance, lightweight alloys explicitly tailored for the PBF-LB/M process is crucial. These lightweight alloys, with optimized strength-to-weight ratios, are essential for advancing sustainability by reducing material usage and improving overall component performance. By developing alloys with a high strength-to-weight ratio, it is possible to ensure the suitability for components that require excellent mechanical properties while remaining light, which is crucial for fuel-dependent industries [71]. Integrating novel lightweight materials in the automotive sector has shown substantial promise, achieving total weight reductions of 20-45% in innovative vehicle designs. Notably, weight reductions of 20-35% have been linked to fuel consumption decreases of 12-20%, underscoring the critical importance of material advancements in driving sustainable and energy-efficient automotive innovation [72]. Lightweight aluminum alloys often replaced traditional steel and iron components, yielding a weight savings of 40-60% with a cost premium of 1.3-2 [73]. Constitutive about 9% of an average vehicle mass [72], aluminum is widely employed in components such as engines (e.g., housing), wheels, and transmissions due to its excellent strength-to-weight ratio, enabling 1 kg of aluminum to replace 2-4 kg of steel. Aluminum alloys play a critical role also in aerospace structures, valued for their lightweight properties and extensively utilized in components such as fuselage skins, upper and lower wing panels, and wing stringers [74]. Innovative aircraft designs are critical for advancing the efficiency and sustainability of modern air travel. Reducing structural weight enables aircraft to carry greater payloads, whether passengers or cargo, without increasing fuel consumption. This optimization translates into lower operational costs, more efficient route planning, and substantially reduced carbon emissions. Notably, a 1% reduction in aircraft weight typically results in an approximate 0.75% decrease in fuel consumption, underscoring the importance of lightweight strategies [75]. The Boeing 787 is a benchmark in leveraging advanced lightweight materials, achieving a 20% weight reduction compared to similar aircraft. This innovation delivers fuel efficiency gains of 10-12%, demonstrating the transformative potential of material advancements in achieving more sustainable aviation practices [76]. High-performance aluminum alloys can provide the mechanical and thermal properties required for specific applications while achieving weight reduction goals. Typical commercial aluminum alloys used in the automotive and aerospace industries are low-cost, age-hardenable wrought aluminum alloys, such as the 2 xxx and 7 xxx series, which have good mechanical properties and can meet a wide range of industrial requirements. However, these alloys are characterized by poor processability due to their high susceptibility to hot cracking caused by rapid melting and solidification [77]. Consequently, the number of these alloys that can be successfully processed using PBF-LB/M and other fusion-based AM processes is quite limited. Currently, the aluminum alloys that can be additively manufactured with lasers are mainly near-eutectic Al-Si-based alloys [78]. This is due to their short solidification range (the temperature range between liquidus and solidus for a material with a distinct chemical composition during which solidification occurs) and consequently their low susceptibility to hot cracking [11]. Although quasi-eutecticcompositions have shown good manufacturability, they fail to meet industrial requirements in terms of mechanical properties and high-temperature performance. Therefore, research into novel, high-performance aluminum alloys compatible with the PBF-LB/M process is continually progressing.