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Research Publications (Engineering and Built Environment)

Permanent URI for this collectionhttp://ir-dev.dut.ac.za/handle/10321/215

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Author: search.filters.author.Mphahlele, Mahlatse R.Subject: search.filters.subject.Nanoindentation

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    Nanoindentation mechanical properties on spark plasma sintered 48Ti-48Al-2Cr-2Nb alloy
    (Elsevier BV, 2021) Mphahlele, Mahlatse R.; Olevsky, Eugene; Tshephe, Thato; Olubambi, Peter A.; Jen, Tien-Chien; Machaka, Ronald; Olubambi, Peter
    This study aims to investigate the microstructure, plastic (H) properties, elastic (E) properties, reduced elastic (Er) properties the strain-to-break parameter (H/Er), and the resistance to plastic deformation parameter (H3/Er2) of the Ti-48Al-2Cr-2Nb alloy by use of scanning electron microscopy, nanoindentation and micro-indentation techniques. The results show that the sintering parameters had significant effect on the resulting microstructure. Desirable mechanical properties were obtained with the sample sintered at temperature of 1200 °C, pressure of 50 MPa, holding time of 7.5 min and a heating rate of 50 °C/min which had a near lamellar structure, resulting from the grain boundary pinning effect of the fine equiaxed gamma grains and the impartation of ductility due to the coarsened lamellar colonies. The nano-hardness and elastic modulus were observed to be about 4GPa and 31GPa for the near lamellar microstructure, respectively, with the microhardness of about 4.4GPa. While the duplex and the near gamma microstructures possessed the least nano-hardness (3.65–3.78GPa) and elastic modulus (3.6–29.5GPa) with the exception of sample sintered at temperature of 1150 °C, pressure of 50 MPa, holding time of 7.5 min and a heating rate of 100 °C/min., with nano-hardness and elastic modulus of 4.05GPa and 31.25GPa, respectively, however it had the lowest micro-hardness of 2.7GPa. Furthermore, the ratios H/Er and H3/Er2 values were observed to be greater for the same sample suggesting good wear resistance of the alloy.
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    Structural characterization and nanoindentation studies on mechanical properties of spark plasma sintered duplex stainless steel nanocomposite
    (Elsevier BV, 2020-11) Oke, Samuel Ranti; Mphahlele, Mahlatse R.; Ige, Oladeji Oluremi; Falodun, Oluwasegun Eso; Okoro, Avwerosuoghene Moses; Olubambi, Peter Apata
    Nano-sized titanium nitride (TiN) powders were used as reinforcements for the fabrication of duplex stainless steel (SAF 2205) via spark plasma sintering (SPS) route. Optimized parameters of 1150 C temperature, 100 C/min heating rate, 50 MPa pressure and 15 min holding time were utilized for sintering of the SAF 2205-TiN composite. SEM equipped with an EBSD and TKD detectors were used to gain insight into sintered composite microstructures and grain boundary character. XRD was used to study crystallinity and phase transformation. The discrete mechanical properties of ferrite/austenite grains and grain boundaries were studied using nanoindentation technique. The addition of TiN nanoparticles resulted in decrease of the a-Fe peaks with principal planes shifting from a-Fe (110) to g-Fe (111). The EBSD confirmed that the addition of TiN nanoparticles to duplex stainless steel could initiate and advance ferrite to austenite phase reverse transformation. The TKD confirmed that nanosized nitrides are concentrated at the ferrite/austenite interface. The nanoindentation studies showed that the nanohardness (H), elastic modulus (E), plasticity index (J), and anti-wear properties were improved with the TiN nanoparticle addition from 0 to 8 wt%.