Desmond Klenam, PhD

University of the Witwatersrand, School of Chemical and Metallurgical Engineering, Researcher & Materials Scientist

University of Oxford, Dept of Materials, Africa Oxford Fellow

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Desmond applies multidisciplinary approaches to challenges in physical metallurgy, academic advisory, and management consulting. I am passionate about teaching, research, and mentoring of young people; my way of putting the next generation in a pole position. I am an analytical, critical, and independent thinker with a knack for challenging conventional wisdom. I approach learning with the heart and mind of a novice and pay attention to details like an expert. Specialty: Alloy development
Desmond had his PhD in Metallurgy and Materials from the University of the Witwatersrand, Johannesburg South Africa. Currently, a visiting scientist at Department of Mechanical Engineering, Worcester Polytechnic Institute, USA.

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Papers by Desmond Klenam, PhD

Effect of nanoscale surface oxide layers on the cold spray of commercially pure titanium and Ti–6Al–4V powders

Computational Materials Science

Effect of aspect ratio on the metal flow behaviour during forming process: a numerical simulation approach

Scientific African, May 1, 2024

Dry sliding wear behavior of experimental low-cost titanium alloys

Tribology transactions, May 24, 2024

Using dynamic materials modelling approach to establish critical parameters for hot coiling of spring steels

Research Square (Research Square), May 22, 2024

This study investigated deformation-induced defects in 55Cr3, 54SiCr6, and 52CrMoV4 spring steels... more This study investigated deformation-induced defects in 55Cr3, 54SiCr6, and 52CrMoV4 spring steels through isothermal compression testing using Gleeble 3500 thermomechanical simulator. The tests were conducted at deformation temperatures of 760, 820, 860, and 920°C, strain rates of 0.1, 1, 5, and 10 s-1 , and a total strain of 0.5. Critical parameters leading to defects were established using power dissipation and instability maps. Microstructural examinations were performed on the deformed samples to validate predictions from power dissipation and instability maps. The results indicated that 55Cr3 spring steel exhibited instability at 850-870°C and 0.3-0.6 s-1 , resulting in rounded cracks and pores in the microstructure. To avoid these defects, this temperature and strain rate range should be avoided during the coiling of 55Cr3 with a ferritic-pearlitic initial microstructure. Both 54SiCr6 and 52CrMoV4 were identified as potential alternatives to 55Cr3, with both alloys primarily undergoing dynamic recovery similar to 55Cr3. However, 54SiCr6 was recommended as the preferred alternative due to its higher power dissipation efficiency of 33% and an optimum deformation region similar to that of 55Cr3.

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Co-Ni-V Ternary Phase Diagram Evaluation

MSI Eureka, May 22, 2024

Hydroxyapatite nano‐pillars on <scp>TI‐6Al‐4V</scp>: Enhancements in cell spreading and proliferation during cell/surface integration

Journal of biomedical materials research. Part A, Apr 17, 2024

On the influence of compositional variations in high chrome cast iron: an assessment of microstructure and mechanical behaviour

Manufacturing review, 2024

In this study, the influence of compositional variation on the microstructure and properties of h... more In this study, the influence of compositional variation on the microstructure and properties of high chrome cast iron produced in jobbing foundries was evaluated. The aim was to determine whether compositional analysis alone is sufficient for qualifying acceptable high chrome cast iron components made in jobbing foundries. The compositions of the melts were analysed using optical emission spectroscopy. They were then compared with targeted compositions for commercially acceptable high chrome cast iron components. Equilibrium phases and phase transition temperatures of the different high chrome cast iron were calculated using the measured compositions as input on Thermo-Calc. Thermal analyses were also carried out to obtain the cooling profiles of each melt using ATAS MetStar software. The predictions from Thermo-Calc and ATAS Metster thermal analyses were then compared with experimentally determined optical and scanning electron images of the alloys. Hardness, fracture toughness, and wear resistance were determined both in the as-cast and heat-treated conditions. The results showed that even slight compositional variations significantly influence the microstructure and mechanical properties of high chrome cast iron, even when the compositions fall within the targeted compositional range typically accepted for industrial applications. Therefore, the study suggests that using compositional analysis alone is not sufficient for accepting high-quality high chrome cast iron components for industrial applications.

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Strain gradient plasticity in AISI A36 plain carbon steel weldment: Comparison of butt and lap joint configurations

Results in engineering, Apr 1, 2024

Corrosion Resistant Materials in High-Pressure High-Temperature Oil Wells: An Overview and Potential Application of Complex Concentrated Alloys

by Fred McBagonluri and Desmond Klenam, PhD

Engineering Failure Analysis, Dec 31, 2023

Data science and material informatics in physical metallurgy and material science: An overview of milestones and limitations

Results in Materials

Mo-Ti-Zr Ternary Phase Diagram Evaluation

MSI Eureka

Robust macroscale superlubricity on carbon-coated metallic surfaces

Applied materials today, Apr 1, 2024

Constitutive analysis of hot metal flow behavior of virgin and rejuvenated heat treatment creep exhausted power plant X20 steel

This paper presents constitutive equations that describe the hot flow behaviour of Virgin (VG) X2... more This paper presents constitutive equations that describe the hot flow behaviour of Virgin (VG) X20 and rejuvenated heat-treated creep exhaust (CE) X20 steels. The study provides a foundation for determining the effect of rejuvenation heat treatment on CE steels by making comparisons to the VG steel. Hot compression tests in the temperature range of 900°C to 1050°C, strain rate range of 0.1–10 s− 1 to a total strain of 0.6 and stress-strain curves were obtained. The flow stress curves of both steels exhibited dynamic recovery (DRV) characteristics as the main softening mechanism. Constitutive constants of steady-state stresses were determined. The stress exponents, n, were 6.62 (VG) and 5.58 (CE), and the apparent activation energy values were 380.36 kJmol− 1(VG) and 435.70 kJmol− 1 (CE). Analysis of the activation energies showed that VG steel had better workability properties than CE steel and was easier to deform at high temperatures. Constitutive equations for predicting the flow...

Strain gradient plasticity phenomenon in surface treated plain carbon steel

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, Apr 1, 2023

Enhanced corrosion performance of low‐cost titanium alloys in a simulated diabetic environment

Materials and Corrosion-werkstoffe Und Korrosion, Jun 12, 2023

Mechanical properties: Fatigue

by Fred McBagonluri and Desmond Klenam, PhD

Elsevier eBooks, 2023

$Research paper thumbnail of A comprehensive review on the deformation behavior of refractory high entropy alloys at elevated temperatures$

A comprehensive review on the deformation behavior of refractory high entropy alloys at elevated temperatures

by Desmond Klenam, PhD, Engr Olufemi, and Akeem Damilola Akinwekomi

Manufacturing review, 2023

Thermo-mechanical processing of refractory high entropy alloys (RHEAs) at high temperatures is ve... more Thermo-mechanical processing of refractory high entropy alloys (RHEAs) at high temperatures is very important. It is an effective method of modifying the microstructure, properties, and shaping into final components after casting. Using the Scopus database, 57 articles relating to the hot deformation of refractory high entropy alloys were extracted from 2011 to 2022. Despite the limited number of articles on hot deformation of RHEAs, it is important to find out if the dominant softening mechanisms reported in other metallic alloys are evident. This is the main impetus for this study since the hot deformation behavior has not been comprehensively studied. All the probable mechanisms influencing deformation in metallic alloys, such as work hardening, dynamic recrystallization, and dynamic recovery, have also been observed in RHEAs. The bulging phenomenon, serrated grain boundaries, and necklace-like structures reported in metallic alloys have also been detected in hot deformed RHEAs. Unsafe deformation behavior such as cracks that have been reported in metallic alloys, have also been observed in RHEAs. This review has provided a comprehensive study on the hot working processes of RHEAs and highlighted critical gaps for future research direction with some suggested limitations.

$Table 3. Top 10 most influential studies on hot deformation of RHEAs. et al. [49] studied the high temperature compression o bo5Moeo5T aos Was and VopNbepMoa9T azgW 209 RHEAs at 600-1600 °C with astrain rate of 0.001s_'. At 600 and 800°C, bysMoo5Ta,W2, RHEA undergoes continuous strength- ening, whereas at higher temperatures (1000-1400°C) it reaches a high stress at an intermediate strain [49]. According to Senkov et al. [49], the strain softening at these temper- atures is an indicator of plastic uncertainty and spallation o the surface material observed at larger strains. At 1600°C, nearly steady state flow at a fixed stress of ~590-600 MPa was observed, and so the yield stress for Nbo;Moo25Tag5 Wo: RHEA steadily decreased as a function of temperature. For the VagNbagMo29Taag W29 RHEA deformed at temperatures (1400 and 1600 °C), a fast decline in yield stress and obvious softening was observed. The flow stress in most metals and alloys decreases with the increase in deformation tempera- ture and the decrease in strain rate [64-67]. Also, when there is a reduction in the strain rate or an increase in the deformation temperature, the critical strain for dynamic recrystallization is decreased. Eleti et al. [32] observed a distinct sharp stress drop around yielding, followed by continuous flow softening, while deforming a Hf{NbTaTiZr RHEA at 1000-1200°C, strain of 0.69, and strain rate of 10~° to 10 *s~!. The sudden drops of the flow stress are visibly detected at initial stages of hot deformation (Fig. 2a). To reveal the mechanism of sharp stress drop, Eleti et al. [32] performed an interrupted deformation test at 1000 °C, held for 600s, and then deformed at a strain rate of 0.001 s (Fig. 2b). The unusual stress drop in the Hf{NbTaTiZr RHEA is due to either dislocation unlocking by solute atoms or the ending of short-range order by dislocation motion. Short- range order can have a profound effect on the stacking-fault energy and dislocation motion, which have noticeable influence on the plastic deformation of HEAs [68]. Similarly, in 2022, Li et al. [69] observed a sharp stress drop in TigZrHfVo 5Tag.2 RHEA at 900-1100 °C and astrain rate of 10° to 10-' s-* (Figs. 2c-e). To reveal the mechanism of sharp stress drop, Li et al. [69] performed an interrupted hot deformation and strain aging experiment (Fig. 2f) at 900°C/0.1s~* with a strain of 0.1 and held for intervals, 0s and 600s. The sharp stress drop was also attributed to the unlocking of dislocations pinned by the Cottrell atmosphere or short-range order. The unusual yield-drop phenomena in RUD Aa arn prnmmaniks pnhanr«and sn allasr pamnnatinana 3 Flow stress behavior of RHEA during hot deformation$

$Fig. 10. Crack propagation in hot compressed refractory high entropy alloys at 800°C (a-e) and 1600°C (f): (a) Broken carbide and rack in TiNbTaZrHf RHEA based composite [104]. (b) Microcracks observed inside the silicides containing Hf{NbTiVSig,,; RHEA [55]. c) Microcracks observed inside the deformed NbyoTizsAlisVioTasHfgzW2 RHEA [41]. (d) Severe cracks at grain boundaries of Wo.4MoNb,TaTi RHEA [76]. (e) Fracture feature of river-like appearance for ZrTiHf{NbMoy RHEA [105]. (f) Propagation of cracks in WReTaMo RHEA [82].$

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Fracture mechanics of carbon steel under different carbon monoxide and dioxide gas mixture conditions in water

Scientific African, Sep 1, 2022

Complex Concentrated Alloys: A Cornucopia of Possible Structural and Functional Applications

Reference Module in Materials Science and Materials Engineering, 2022

Prediction of stress-corrosion cracking using electrochemical noise measurements: A case study of carbon steels exposed to H2O-CO-CO2 environment

Engineering Failure Analysis, Feb 1, 2023

Desmond Klenam, PhD

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