Dr. Suib is a Board of Trustees Distinguished Professor of Chemistry and received the CT Medal of Science for his work in catalysis, semiconductors and ceramic composites. He received a B. S. degree in chemistry and geology at the State University College of New York at Fredonia. His graduate and postdoctoral training was completed at the University of Illinois at Champaign Urbana. In 1980, Steve joined UConn’s faculty in the Department of Chemistry and served as the head of the department for 10 years. He is a Fellow of the American Chemical Society and the American Institute of Chemists.

Materials by Design

Bare and nonionic surfactant-functionalized praseodymium oxide nanoparticles: Toxicological studies.

Advanced Materials Research

Investigation on the influence of SiC particle parameters on the machinability of SiCp/Al composite

The present study evaluated hardness, tensile properties and two-body abrasive wear behaviour of Al–Mg–Si alloy specimens artificially aged at 448 K for different durations ranging from 0.5 to 504 h. In addition to the measurements of Vickers hardness and tensile properties, wear tests of differently aged alloys were conducted against SiC abrasive paper of 220 grit size under normal load of 9.81 N with the help of a pin-on-disc tribometer. Abrasive wear characteristics were assessed in terms of measurements of specific wear rate and roughness of the abraded surfaces. These were substantiated via examinations of worn surfaces, collected wear debris and subsurfaces of worn specimens to comprehend the micro-mechanisms of abrasion. The abrasive wear performance varied significantly with the duration of artificial aging and the lowest specific wear rate as well as roughness of the abraded surfaces corresponded to the peak-aged condition. An attempt was also made to correlate mechanical properties and tribological performance. It was found that the specific wear rate exhibited direct linear relation with the strain hardening exponent, and inverse linear relationships with hardness, yield strength and strength coefficient. Microplowing, microcutting and microcracking were identified as mechanisms of abrasion; the extents of these processes were found to be governed by the state of aging that determined the mechanical properties.

Influence of Artificial Aging on Mechanical Properties and High Stress Abrasive Wear Behaviour of Al–Mg–Si Alloy

This study examined the effects of heat treatment on the microstructure and wear properties of Al–Zn–Mg–Cu/in-situ Al–9Si–SiCp/pure Al composites. Pure Al powder was used to increase densification but it resulted in heterogeneous precipitation as well as differences in hardness among the grains. Heat treatment was conducted to solve this problem. The heat treatment process consisted of three stages: solution treatment, quenching, and aging treatment. After the solution treatment, the main dissolved phases were η′(Mg4Zn7), η(MgZn2), and Al2Cu phase. An aging treatment was conducted over the temperature range, 100–240 °C, for various times. The GP zone and η′(Mg4Zn7) phase precipitated at a low aging temperature of 100–160 °C, whereas the η(MgZn2) phase precipitated at a high aging temperature of 200–240 °C. The hardness of the sample aged at 100–160 °C was higher than that aged at 200–240 °C. The wear test was conducted under various linear speeds with a load of 100 N. The aged composite showed a lower wear rate than that of the as-sintered composite under all conditions. As the linear speed was increased to 1.0 m/s, the predominant wear behavior changed from abrasive to adhesive wear in all composites.

Effect of Heat Treatment on the Microstructure and Wear Properties of Al–Zn–Mg–Cu/In-Situ Al–9Si–SiCp/Pure Al Composite by Powder Metallurgy

The newly designed Ti-based bulk metallic glass (BMG) in which case of fracture behavior was observed 1990MPa to compressive strength with a wide plastic deformation around 7% after process of elastic deformation. This phenomenon can be compared with those of Ti-based alloys and other Ti-based BMGs and indicates high potential to be applied in use. It was evaluated the Ti-based BMG for thermal stability that the reduced glass parameters, ΔTx, Trg and γ, are 79K, 0.50 and 0.38, respectively. In addition, it reveals high activation energies for crystallization in which are estimated to Ex1 = 291.77 ±9.71 kJ/mol, Ex2 = 588.77 ±28.88 kJ/mol and Ex3 = 330.26 ±3.61 kJ/mol on kissinger plotting in this study.

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Effect of Hafnium and Zirconium to Glass Forming Ability, Thermal Stability, Plasticity Deformation and Crystallization of Ni-Free Pentabasic Ti-Based Bulk Metallic Glasses

Among various processes for manufacturing complex-shaped metal parts, additive manufacturing is highlighted as a process capable of reducing the wastage of materials without requiring a post-process, such as machining and finishing. In particular, it is a suitable new manufacturing technology for producing AISI H13 tool steel for hot-worked molds with complex cooling channels. In this study, we manufactured AISI H13 tool steel using the laser power bed fusion (LPBF) process and investigated the effects of tempering temperature and holding time on its microstructure and mechanical properties. The mechanical properties of the sub-grain cell microstructure of the AISI H13 tool steel manufactured using the LPBF process were superior to that of the H13 tool steel manufactured using the conventional method. These sub-grain cells decomposed and disappeared during the austenitizing process; however, the mechanical properties could be restored at a tempering temperature of 500 °C or higher owing to the secondary hardening and distribution of carbides. Furthermore, the mechanical properties deteriorated because of the decomposition of the martensite phase and the accumulation and coarsening of carbides when over-tempering occurred at 500 °C for 5 h and 550 °C for 3 h.

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Influence of Tempering Temperature and Time on Microstructure and Mechanical Properties of Additively Manufactured H13 Tool Steel

To investigate the effect of Fe content on the correlation between the microstructure and mechanical properties in near-b titanium alloys, the Ti-5Al-5Mo-5V-1Cr-xFe alloy system has been characterized in this study. As the Fe content increased, the number of nucleation sites and the volume fraction of the α phase decreased. We observed a significant difference in the shape and size of the α phase in the matrix before and after Fe addition. In addition, these morphological deformations were accompanied by a change in the shape of the α phase, which became increasingly discontinuous, and changed into globular-type α phase in the matrix. These phenomena affected the microstructure and mechanical properties of Ti alloys. Specimen #2 exhibited a high ultimate tensile strength (1071 MPa), which decreased with further addition of Fe.

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Ki-Chang Bae

Papers

Effect of Heat Treatment on the Microstructure and Wear Properties of Al–Zn–Mg–Cu/In-Situ Al–9Si–SiCp/Pure Al Composite by Powder Metallurgy

Effect of Hafnium and Zirconium to Glass Forming Ability, Thermal Stability, Plasticity Deformation and Crystallization of Ni-Free Pentabasic Ti-Based Bulk Metallic Glasses

Influence of Tempering Temperature and Time on Microstructure and Mechanical Properties of Additively Manufactured H13 Tool Steel

Effect of Fe Content on the Microstructure and Mechanical Properties of Ti-Al-Mo-V-Cr-Fe Alloys

Structural evaluation in the isothermal treated non-stoichiometric bismuth ferrite by Raman spectroscopy