The microstructure evolution and room temperature deformation behavior of ferrite-based lightweight steel

Nezhadfar, P.D.,Zarei-Hanzaki, A.,Sohn, S.S.,Abedi, H.R. Elsevier Sequoia 2016 Materials science & engineering. properties, micro Vol.665 No.-

<P>The microstructure evolution and room temperature deformation behavior of a duplex advanced ferrite based lightweight steel was investigated through compression testing method. In order to trace the microstructure evolution, the tests were interrupted at the true strains of 0.05, 0.1, 0.15, 0.3 and 0.6. The occurrence of deformation bands in ferrite phase is characterized as the main feature of the developed microstructure under the specified regime and the frequency of deformation bands increases by increasing the imposed strain. To well assess the nature of these deformation bands, electron back scattered diffraction analysis is employed. The results approve that deformation bands are in twin relation with the ferrite matrix. The twins are characterized in conventional (112)[111] system with 60 misorientation and present three point coincidence type pole figures. The ferrite twins are formed in a specific orientation relationship with its mother ferrite orientation thereby strongly affect the strain distribution pattern. The twinning occurrence in ferrite matrix is believed to be as the influencing factor of the observed load fluctuations at the early stage of deformation and at relatively high stress level. (C) 2016 Elsevier B.V. All rights reserved.</P>

Evolution of microstructure and mechanical properties in a hypoeutectic Al-Si-Mg alloy processed by accumulative back extrusion

Haghdadi, N.,Zarei-Hanzaki, A.,Abedi, H.R.,Abou-Ras, D.,Kawasaki, M.,Zhilyaev, A.P. Elsevier Sequoia 2016 Materials science & engineering. properties, micro Vol.651 No.-

<P>This study demonstrates the evolution of microstructure and mechanical properties of a hypoeutectic Al-7Si-0.4Mg (A356) alloy processed by accumulative back extrusion (ABE) at temperatures ranging from 200 to 500 degrees C. ABE processing is one of the new severe plastic deformation techniques enabling one to produce relatively large ultrafine-grained materials in a cylindrical shape. One complete pass of ABE was estimated to introduce a reasonably homogeneous effective strain of similar to 3 as calculated by finite element analysis. Microstructural observation showed that globular alpha-Al primary phase was subdivided into fine substructures and Si particles having a fibrous shape were fragmented and spheroidized within the eutectic constituent through ABE processing. There was no evidence of homogeneous distribution of the fine Si particles in the alpha-Al phase after ABE. Mechanical testing at room temperature showed that both yield strength and ultimate tensile strength of the A356 alloy dramatically increased through ABE, especially at lower processing temperatures, as compared with the as-cast condition whereas there was no significant reduction in ductility at all processing temperatures. The experimental results were discussed with emphasis on the microstructure evolution involving dynamic recrystallization and deformation behavior including strengthening mechanisms and strain hardening in the Al-Si alloy. (C) 2015 Elsevier B.V. All rights reserved.</P>

Outstanding Mild Wear Performance of Ti–29Nb–14Ta–4.5Zr Alloy Through Subsurface Grain Refinement and Supporting Effect of Transformation Induced Plasticity

Farahnaz Haftlang,Abbas Zarei‑Hanzaki,Hamid Reza Abedi,Joraslov Málek,Ehsan Farabi,Hossein Beladi 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.4

The tribological performance of Ti–29Nb–14Ta–4.5Zr alloy against Ti–6Al–4V ELI was investigated for the mild condition,emphasized on the superficial changes and changes underneath the wear track. The results of X-ray photoelectronspectroscopy indicated that TiO2,Nb2O,Ta2Oand Zr2Ooxides aggregated to form a protective tribo-layer, which effectivelyprevented further superficial damages. Development of fine-grain layer and the occurrence of phase transformation ofβ → α’’/ω were characterized as the main wear-induced evolution of the subsurface layer. The wear-induced transformationincreases the hardenability of the subsurface layer, effectively support the worn surface and prevent premature cracking. These phenomenal evolutions were led to a simultaneous increase in the strength and ductility and subsequently wear lossreduction in comparison to the Ti64 ELI.

Trading off between dynamic strain aging and substructure evolution in κ-carbide-free lightweight steel at room temperature

Abedi, H.R.,Zarei Hanzaki, A.,Nemati, N.,Kim, Dae-Eun Elsevier 2018 Scripta materialia Vol.157 No.-

<P><B>Abstract</B></P> <P>The previous proposed models to describe the room temperature dynamic strain aging of twinning-induced-plasticity steels appear to be theoretically invalid in the case of lightweight grades. The proposed theory in the present work accentuates the high capability of the experimented dilute solid solution in progressive formation and refinement of the cell structures. The higher dislocation population in the cell-walls in comparison to that of cell-interiors is viable enough to increase the stress assisted drift and stimulate the sub-boundaries preferred sites to accommodate the solutes. The short-range dislocation core diffusion enables the cell-walls to assist the strain aging to occur.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Characterization of Twin-Like Structure in a Ferrite-Based Lightweight Steel

Pooriya Dastranjy Nezhadfar,Abbas Zarei-Hanzaki,Seok Su Sohn,Hamid Reza Abedi 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.5

The present study examined cold to warm compressive deformation behavior of a ferrite- based lightweight steel through characterization of the banded structures. Compression tests were carried out at 25 to 500 °C at a strain rate of 0.01 s -1 up to true strain of 0.6. Analysis of the microstructural evolution using electron back scatter diffraction indicated that the twin-like bands in the large ferrite grains occurred with the {112}[111] system at a 60° misorientation. Density of the twin-like bands is increased by raising the deformation temperature. EBSD results showed that the primary and secondary twins occurred in the [-11-1] and [1-1-1] directions. In addition, the strain at 500 °C distorted the twin-like bands and resulted in wavy boundaries. The strain hardening behavior was also examined using the Crussard-Jaoul (C-J) model and the n-values were calculated for each stage of imposing strain. The results showed high dislocation density in the adjacent of twin-like boundaries intersections which resulted in the n-value increment.

Nanostructured β-type titanium alloy fabricated by ultrasonic nanocrystal surface modification

Kheradmandfard, Mehdi,Kashani-Bozorg, Seyed Farshid,Kim, Chang-Lae,Hanzaki, Abbas Zarei,Pyoun, Young-Shik,Kim, Jung-Hyong,Amanov, Auezhan,Kim, Dae-Eun Elsevier 2017 Ultrasonics sonochemistry Vol.39 No.-

<P><B>Abstract</B></P> <P>The surface of β-type Ti-Nb-Ta-Zr (TNTZ) alloy, which is a promising material for biomedical applications, was treated with the ultrasonic nanocrystal surface modification (UNSM) technique to enhance its hardness. As a result, a gradient nanostructured (GNS) layer was generated in the surface; the microstructure of the top surface layer consisted of nanoscale lamellae with a width of about 60–200nm. In addition, there were lamellar grains consisting of nanostructured subgrains having unclear and wavy boundaries. The treated surface exhibited a hardness value of ∼385HV compared to 190HV for the untreated alloy. It was further determined that highly dense deformation twins were generated at a depth of ∼40–150µm below the UNSM-treated surface. These deformation twins led to a significant work hardening effect which aided in enhancing the mechanical properties. It was also found that UNSM treatment resulted in the formation of micropatterns on the surface, which would be beneficial for high bioactivity and bone regeneration performance of TNTZ implants.</P> <P><B>Highlights</B></P> <P> <UL> <LI> UNSM is a method that utilizes ultrasonic vibration to generate nanostructured surface. </LI> <LI> The surface of β-type Ti-Nb-Ta-Zr (TNTZ) alloy was treated with the UNSM technique. </LI> <LI> A gradient nanostructured layer was generated in the surface. </LI> <LI> Top surface layer consisted of nanoscale lamellae with a width of about 60–200nm. </LI> <LI> Hardness of treated surface was ∼385HV compared to 190HV for the untreated alloy. </LI> </UL> </P>

Significant improvement in cell adhesion and wear resistance of biomedical β-type titanium alloy through ultrasonic nanocrystal surface modification

Kheradmandfard, Mehdi,Kashani-Bozorg, Seyed Farshid,Lee, Jung Seung,Kim, Chang-Lae,Hanzaki, Abbas Zarei,Pyun, Young-Sik,Cho, Seung-Woo,Amanov, Auezhan,Kim, Dae-Eun Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.762 No.-

<P><B>Abstract</B></P> <P>A novel β-type Ti–29Nb–13Ta–4.6Zr (TNTZ) alloy with a low Young's modulus, high bio-corrosion resistance, and excellent biocompatibility has been recently introduced for implant applications. Here, ultrasonic nanocrystal surface modification (UNSM) treatment was applied to TNTZ alloy to improve its wear resistance and biofunctionality. Application of UNSM to a TNTZ alloy resulted in the generation of a nanostructured surface layer. The wear resistance of the UNSM-treated specimen was observed to be more than 7 times higher than that of the untreated one. Cell culture tests indicated that MC3T3 cells adhered and spread more readily on the UNSM-treated specimen than on the untreated one. MTT assays after 1 and 4 days in culture also indicated enhancement of cell proliferation on the UNSM-treated specimen than that of the untreated one. Live/dead assay revealed no significant cytotoxicity in either substrate. The significant improvement of cell adhesion, spreading, and proliferation on the UNSM-treated TNTZ alloy specimen were attributed to both grain refinement and micro-patterned surface effects. These results demonstrate that UNSM-treatment not only improves the wear resistance of TNTZ alloy, but also enhances its biocompatibility, which makes it a strong candidate for applications in medical implants.</P> <P><B>Highlights</B></P> <P> <UL> <LI> UNSM treatment was applied to a β titanium alloy to generate nanostructured surface. </LI> <LI> The wear resistance of the UNSM-treated specimen was significantly improved. </LI> <LI> Treated specimens showed significant improvement of cell adhesion and proliferation. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Simultaneous grain refinement and nanoscale spinodal decomposition of β phase in Ti-Nb-Ta-Zr alloy induced by ultrasonic mechanical impacts

Kheradmandfard, Mehdi,Kashani-Bozorg, Seyed Farshid,Kang, Kyeong-Hee,Penkov, Oleksiy V.,Zarei Hanzaki, Abbas,Pyoun, Young-Shik,Amanov, Auezhan,Kim, Dae-Eun Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.738 No.-

<P><B>Abstract</B></P> <P>It was found that ultrasonic nanocrystal surface modification (UNSM) treatment performed on Ti-Nb-Ta-Zr (TNTZ) alloy surface to produce a gradient nanostructured surface layer also resulted in the nano-scale spinodal decomposition of β phase. For the first time, nano-scale spinodal decomposition of β phase induced by ultrasonic mechanical impacts was observed in a short time without any age treatment. The peak shift of XRD to lower angles, (110) β XRD peak splitting, overlapped and asymmetric XRD peaks, satellite reflections in the SAED pattern, and lattice straining in HR-TEM images confirmed nano-scale spinodal decomposition of β phase in the TNTZ alloy induced by UNSM treatment. Nano-scale EDS line-scan probe analysis revealed the β phase separation into nano-scale domains of Ti-rich (β<SUB>1</SUB>) and Ti-depleted (β<SUB>2</SUB>) phases. HR-TEM images showed the semi-coherent arrangement of Ti-rich (β<SUB>1</SUB>) and Ti-depleted (β<SUB>2</SUB>) regions. Nanosized grain formation and spinodal decomposition of β phase were induced simultaneously by UNSM treatment. The nano-scale grains, high dislocation density, and semi-coherent interface between the spinodally separated phases contributed to the high hardness of the UNSM-treated TNTZ alloy specimen.</P> <P><B>Highlights</B></P> <P> <UL> <LI> UNSM is a method that applies ultrasonic impacts to generate nanostructured surface. </LI> <LI> UNSM was applied to the surface of TNTZ alloy. </LI> <LI> Gradient nanostructured layer was produced in the top surface. </LI> <LI> Nano-scale spinodal decomposition of β phase induced by ultrasonic impacts. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>