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Effect of pores on mechanical properties of 3D printed titanium alloys

The presence of porosity in 3D-printed titanium alloys can significantly impact their mechanical properties, especially fatigue performance.Here's how porosity affects the mechanical properties:

• Fatigue Resistance: Micro-pores can act as fatigue crack initiation sites, which reduces the fatigue performance of 3D-printed components. Even for dense samples of 3D-printed Ti-6Al-4V alloy, these micro-pores don't greatly affect static mechanical properties but can lead to early crack formation under cyclic loading.

• Tensile Properties: High porosity can lead to decreased tensile strength.

• Ductility: High porosity can lead to decreased ductility and reduced fatigue life.

• Other properties: The influence of pores also extends to overall structural integrity, affecting density and potentially leading to cracking.

To mitigate the negative effects of porosity, several strategies can be employed:

• Optimized Protective Gases: Using optimized mixed protective gases like argon-helium mixtures can reduce spatter and defects during the printing process, thereby improving the overall surface quality and reducing porosity.

• Hot Isostatic Pressing (HIP): HIP treatment can close pores and improve the fatigue strength of both dense and porous 3D-printed Ti-6Al-4V alloy samples. • Parameter Adjustment: Adjusting parameters such as laser power and beam movement speed can eliminate fusion defects.

• Powder Density Control: Increasing powder packing density can reduce porosity.

• NAMP (Net-Additive Manufacturing Process): This process allows for the refinement of the microstructure without causing pore recurrence.