Processing and characterization of crack-free 7075 aluminum alloys with elemental Zr modification by laser powder bed fusion

Wenhui Yu, Zhen Xiao, Xuhui Zhang, Yetao Sun, Peng Xue, Shuai Tan, Yongling Wu, Hongyu Zheng

Article ID: 4
Vol 1, Issue 1, 2022, Article identifier:4


High-performance engineering alloys, such as 7000 series aluminum alloys, suffer poor printability in laser powder bed fusion (LPBF) additive manufacturing. An enormous challenge lies in the suppression of solidification cracks caused by solidification shrinkage and thermal stresses. Porosity formation, as one of the main concerns for LPBF application, should also be avoided at the same time. In this study, aluminum alloy (AA) 7075 with and without Zr modification was additively manufactured by LPBF. Processing parameters of laser power and scanning speed, resulting in various volumetric energy density (VED), were experimentally determined to produce crack-free components with tailored microstructure. Optical microscopy was used to reveal how the crack density and porosity vary with VED. Scanning electron microscopy and transmission electron microscopy uncovered the detailed microstructure in the molten pool and the evolution of the elemental Zr addition. The results indicate that 1 w.t.% addition of elemental Zr in AA7075 led to lower crack density compared with 0.3 w.t.% addition. In 1 w.t.% Zr-modified AA7075, crack-free components were obtained under high VED. Fine equiaxed grains, instead of large columnar grains, were formed at the bottom of the molten pool boundary due to the existence of Al3Zr compound, which favored the nucleation of aluminum grains and elimination of cracks. The phenomenon of silicon segregation near cracks remained in Zr modified alloys, although its effects on cracking were suppressed. Spherical pores in the Zr-modified AA7075 increased due to the deterioration of fluidity by unmelted particles, which distracted the Marangoni flow as well. Sufficient laser energy input can increase the viscosity and ease the pores escaping. By optimizing parameters, crack-free AA7075 parts with low porosity can be manufactured through LPBF with Zr addition.


Laser powder bed fusion; 7075 aluminum alloys; Zr modification; Crack elimination; Porosity

Full Text:



Zhang D, Qiu D, Gibson MA, et al., 2019, Additive manufacturing of ultrafine-grained high-strength titanium alloys. Nature, 576: 91–95.

Wei C, Li L, 2021, Recent progress and scientific challenges in multi-material additive manufacturing via laser-based powder bed fusion. Virtual Phys Prototyp, 16: 347–371.

Sing SL, Huang S, Goh GD, et al., 2021, Emerging metallic systems for additive manufacturing: In-situ alloying and multi-metal processing in laser powder bed fusion. Prog Mater Sci, 119: 100795.

Zhou Y, Wang J, Yang Y, et al., 2022, Laser additive manufacturing of zinc targeting for biomedical application. Int J Bioprinting, 8: 501.

Zhang Y, Attarilar S, Wang L, et al., 2021, A review on design and mechanical properties of additively manufactured NiTi implants for orthopedic applications. Int J Bioprinting, 7: 340–340.

Gu D, Ma C, Dai D, et al., 2021, Additively manufacturing-enabled hierarchical NiTi-based shape memory alloys with high strength and toughness. Virtual Phys Prototyp, 16(Suppl 1): S19–S38.

Yu WH, Sing SL, Chua CK, et al., 2019, Particle-reinforced metal matrix nanocomposites fabricated by selective laser melting: A state of the art review. Prog Mater Sci, 104: 330– 379.

Xie B, Zhao MC, Xu R, et al., 2020, Biodegradation, antibacterial performance, and cytocompatibility of a novel ZK30-Cu-Mn biomedical alloy produced by selective laser melting. Int J Bioprinting, 7: 300–300.

Xue L, Atli KC, Zhang C, et al., 2022, Laser powder bed fusion of defect-free NiTi shape memory alloy parts with superior tensile superelasticity. Acta Mater, 229: 117781.

Mukherjee T, DebRoy T, 2018, Mitigation of lack of fusion defects in powder bed fusion additive manufacturing. J Manuf Process, 36: 442–449.

Yonehara M, Kato C, Ikeshoji TT, et al., 2021, Correlation between surface texture and internal defects in laser powder-bed fusion additive manufacturing. Sci Rep UK, 11: 22874.

Moon S, Ma R, Attardo R, et al., 2021, Impact of surface and pore characteristics on fatigue life of laser powder bed fusion Ti-6Al-4V alloy described by neural network models. Sci Rep UK, 11: 20424.

Tang M, Pistorius PC, Beuth JL, 2017, Prediction of lack-of-fusion porosity for powder bed fusion. Addit Manuf, 14: 39–48.

Plessis AD, 2019, Effects of process parameters on porosity in laser powder bed fusion revealed by X-ray tomography. Addit Manuf, 30: 100871.

Leung CL, Marussi S, Atwood RC, et al., 2018, In situ X-ray imaging of defect and molten pool dynamics in laser additive manufacturing. Nat Commun, 9: 1355.

Yu W, Sing SL, Chua CK, et al., 2019, Influence of re-melting on surface roughness and porosity of AlSi10Mg parts fabricated by selective laser melting. J Alloys Compd, 792: 574–581.

Martin JH, Yahata BD, Hundley JM, et al., 2017, 3D printing of high-strength aluminium alloys. Nature, 549: 365–369.

Aucott L, Dong H, Mirihanage W, et al., 2018, Revealing internal flow behaviour in arc welding and additive manufacturing of metals. Nat Commun, 9: 5414.

Hyer H, Zhou L, Mehta A, et al., 2021, Composition-dependent solidification cracking of aluminum-silicon alloys during laser powder bed fusion. Acta Mater, 208: 116698.

Hyer H, Zhou L, Mehta A, et al., 2021, Effects of alloy composition and solid-state diffusion kinetics on powder bed fusion cracking susceptibility. J Phase Equilib Diffus, 42: 5–13.

Riener K, Pfalz T, Funcke F, et al., 2022, Processability of high-strength aluminum 6182 series alloy via laser powder bed fusion (LPBF). Int J Adv Manuf Technol, 119: 4963– 4977.

Tan Q, Fan Z, Tang X, et al., 2021, A novel strategy to additively manufacture 7075 aluminium alloy with selective laser melting. Mater Sci Eng A, 821: 141638.

Li G, Li X, Guo C, et al., 2022, Investigation into the effect of energy density on densification, surface roughness and loss of alloying elements of 7075 aluminium alloy processed by laser powder bed fusion. Opt Laser Technol, 147: 107621.

Stopyra W, Gruber K, Smolina I, et al., 2020, Laser powder bed fusion of AA7075 alloy: Influence of process parameters on porosity and hot cracking. Addit Manuf, 35: 101270.

Zhu Z, Ng FL, Seet HL, et al., 2021, Superior mechanical properties of a selective-laser-melted AlZnMgCuScZr alloy enabled by a tunable hierarchical microstructure and dual-nanoprecipitation. Mater Today,

Lei Z, Bi J, Chen Y, et al., 2019, Effect of energy density on formability, microstructure and micro-hardness of selective laser melted Sc- and Zr- modified 7075 aluminum alloy. Powder Technol, 356: 594–606.

Shrivastava V, Singh P, Gupta GK, et al., 2021, Synergistic effect of heat treatment and reinforcement content on the microstructure and corrosion behavior of Al-7075 alloy based nanocomposites. J Alloys Compd, 857: 157590.

Liu L, Jiang JT, Cui XY, et al., 2022, Correlation between precipitates evolution and mechanical properties of Al-Sc-Zr alloy with Er additions. J Mater Sci Technol, 99: 61–72.

Qi Y, Hu Z, Zhang H, et al., 2021, High strength Al-Li alloy development for laser powder bed fusion. Addit Manuf, 47: 102249.

Otani Y, Sasaki S, 2020, Effects of the addition of silicon to 7075 aluminum alloy on microstructure, mechanical properties, and selective laser melting processability. Mater Sci Eng A, 777: 139079.

Glerum JA, Kenel C, Sun T, et al., 2020, Synthesis of precipitation-strengthened Al-Sc, Al-Zr and Al-Sc-Zr alloys via selective laser melting of elemental powder blends. Addit Manuf, 36: 101461.

Zhu Y, Zhao Y, Chen B, 2022, A study on Sc- and Zr-modified Al-Mg alloys processed by selective laser melting. Mater Sci Eng A, 833: 142516.

Mehta A, Zhou L, Huynh T, et al., 2021, Additive manufacturing and mechanical properties of the dense and crack free Zr-modified aluminum alloy 6061 fabricated by the laser-powder bed fusion. Addit Manuf, 41: 101966.

Hyer H, Zhou L, Park S, et al., 2022, Elimination of extraordinarily high cracking susceptibility of aluminum alloy fabricated by laser powder bed fusion. J Mater Sci Technol, 103: 50–58.

Li P, Li R, Yang H, et al., 2021, Selective laser melting of Al-3.48Cu-2.03Si-0.48Sc-0.28Zr alloy: Microstructure evolution, properties and metallurgical defects. Intermetallics, 129: 107008.

Zhang X, Xiao Z, Yu W, et al., 2022, Influence of erbium addition on the defects of selective laser-melted 7075 aluminium alloy. Virtual Phys Prototyp, 17: 406-418.

Martin A, Vilanova M, Gil E, et al., 2022, Influence of the Zr content on the processability of a high strength Al-Zn- Mg-Cu-Zr alloy by laser powder bed fusion. Mater Charact, 183: 111650.

Hojjatzadeh SMH, Parab ND, Guo Q, et al., 2020, Direct observation of pore formation mechanisms during LPBF additive manufacturing process and high energy density laser welding. Int J Mach Tools Manuf, 153: 103555.

Gu D, Yuan P, 2015, Thermal evolution behavior and fluid dynamics during laser additive manufacturing of Al-based nanocomposites: Underlying role of reinforcement weight fraction. J Appl Phys, 118: 233109.

Gu D, Ma C, Xia M, et al., 2017, A Multiscale understanding of the thermodynamic and kinetic mechanisms of laser additive manufacturing. Engineering PRC, 3: 675-684.

Khvan AV, Eskin DG, Starodub KF, et al., 2018, New insights into solidification and phase equilibria in the Al-Al3Zr system: Theoretical and experimental investigations. J Alloys Compd, 743: 626–638.

Uddin SZ, Murr LE, Terrazas CA, et al., 2018, Processing and characterization of crack-free aluminum 6061 using high-temperature heating in laser powder bed fusion additive manufacturing. Addit Manuf, 22: 405–415.



  • There are currently no refbacks.

Copyright (c) 2022 Author(s)

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.