Microstructural evolution and mechanical properties of Ti-6Al-4V wall deposited by pulsed plasma arc additive manufacturing

The IN738LC Ni-based superalloy strengthened by the coherent γ′-Ni3(Al,Ti) intermetallic compound is one of the most employed blade materials in gas turbine engines and IN738LC thin wall components without macro-cracks were fabricated by pulsed plasma arc additive manufacturing (PPAAM), which is more competitive when considering convenience and cost in comparison with other high-energy beam additive manufacturing technologies. The as-fabricated sample exhibited epitaxial growth columnar dendrites along the building direction with discrepant secondary arm spacing due to heat accumulation. A lot of fine γ′ particles with an average size of 81 nm and MC carbides were observed in the interdendritic region. Elemental segregation and γ–γ′ eutectic reaction were analyzed in detail and some MC carbides were confirmed in the reaction L + MC→γ + γ′. After standard heat treatment, bimodal distribution of γ′ phases, including coarse γ′ particles (385 nm, 42 vol.%) and fine γ′ particles (42 nm, 25 vol.%), was observed. The mechanism of microstructural evolution, phase formation, as well as cracking mechanisms were discussed. Microhardness and tensile tests were carried out to investigate the mechanical performance. The results show that both the as-fabricated and heat-treated samples exhibited a higher tensile strength but a slightly lower ductility compared with cast parts.

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Laser Additive Manufacturing of Novel Aluminum Based Nanocomposite Parts: Tailored Forming of Multiple Materials

Journal of Manufacturing Science and Engineering ◽

10.1115/1.4030376 ◽

2015 ◽

Vol 138 (2) ◽

Cited By ~ 7

Author(s):

Dongdong Gu ◽

Hongqiao Wang ◽

Donghua Dai

Keyword(s):

Mechanical Properties ◽

Additive Manufacturing ◽

Microstructural Evolution ◽

Mechanical Performance ◽

Laser Energy ◽

Dimensional Accuracy ◽

Ring Structure ◽

Multiple Materials ◽

Depth Relationship ◽

Tailored Forming

The present study has proved the feasibility to produce the bulk-form TiC/AlSi10Mg nanocomposite parts with the novel reinforcing morphology and enhanced mechanical properties by selective laser melting (SLM) additive manufacturing (AM) process. The influence of linear laser energy density (η) on the microstructural evolution and mechanical performance (e.g., densification level, microhardness, wear and tribological properties) of the SLM-processed TiC/AlSi10Mg nanocomposite parts was comprehensively studied, in order to establish an in-depth relationship between SLM process, microstructures, and mechanical performance. It showed that the TiC reinforcement in the SLM-processed TiC/AlSi10Mg nanocomposites experienced an interesting microstructural evolution with the increase of the applied η. At an elevated η above 600 J/m, a novel regularly distributed ring structure of nanoscale TiC reinforcement was tailored in the matrix due to the unique metallurgical behavior of the molten pool induced by the operation of Marangoni flow. The near fully dense TiC/AlSi10Mg nanocomposite parts (>98.5% theoretical density (TD)) with the formation of ring-structured reinforcement demonstrated outstanding mechanical properties. The dimensional accuracy of SLM-processed parts well met the demand of industrial application with the shrinkage rates of 1.24%, 1.50%, and 1.72% in X, Y, and Z directions, respectively, with the increase of η to 800 J/m. A maximum microhardness of 184.7 HV0.1 was obtained for SLM-processed TiC/AlSi10Mg nanocomposites, showing more than 20% enhancement as compared with SLM-processed unreinforced AlSi10Mg part. The high densification response combined with novel reinforcement of SLM-processed TiC/AlSi10Mg nanocomposite parts also led to the considerably low coefficient of friction (COF) of 0.28 and wear rate of 2.73 × 10−5 mm3 · N−1 · m−1. The present work accordingly provides a fundamental understanding of the tailored forming of lightweight multiple nanocomposite materials system by laser AM.

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