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Behjati, P.,Kermanpur, A.,Najafizadeh, A.,Samaei Baghbadorani, H.,Karjalainen, L.P.,Jung, J.G.,Lee, Y.K. Scientific and Technical Press ; Elsevier Science 2014 MATERIALS AND DESIGN Vol.63 No.-
A conceptual approach was used to design a new Ni-free austenitic stainless steel with a unique combination of ultrahigh strength and ductility. The concept was based on the alloying of the 0.05C-18Cr-12Mn (wt.%) steel by 0.39%N and heavy warm rolling (84% reduction) at 1173K (900<SUP>o</SUP>C) to achieve the yield strength of minimum 1GPa and high tensile strength and elongation due to a proper stability of the austenite as a result of the optimized stacking fault energy (SFE). The yield strength of 1010MPa, tensile strength of 1150MPa and high fracture strain of 70% were measured for the steel designed. Dislocation and solid solution hardening mechanisms are introduced as the main contributors for the ultrahigh yield strength of the steel. The strain hardening is gradual and the hardening rate reaches a high level of ~2400MPa at a high true strain of 40% due to slow α'-martensitic transformation and mechanical twinning. Consequently, the ductility of the designed steel is excellent.
Behjati, P.,Kermanpur, A.,Najafizadeh, A.,Baghbadorani, H.S.,Jung, J.G.,Lee, Y.K. Elsevier Sequoia 2014 Materials science & engineering. properties, micro Vol.614 No.-
In this work, the influence of precooling on deformation-induced α'-martensitic transformation and mechanical properties of Fe-16Mn-4Cr-0.1C (wt%) austenitic steel is investigated. It is shown that precooling in liquid nitrogen enhances the volume fraction of ε-martensite. During tensile testing, ε-martensite acts as a nucleation site for α'-martensite and promotes the strength and ductility of the steel. The precooled steel exhibits an excellent combination of mechanical properties (tensile strength of 1240MPa, uniform elongation of 35% and total elongation of 42%). Further, it is shown that tensile strength and elongation of the steel strongly depend on the deformation temperature. This is explained by the influence of temperature on stacking fault energy (SFE) and accordingly governing deformation mechanisms of the steel.
Behjati, P.,Kermanpur, A.,Najafizadeh, A.,Samaei Baghbadorani, H.,Jung, J.G.,Lee, Y.K. Elsevier Sequoia 2014 Materials science & engineering. properties, micro Vol.610 No.-
In this work, a specific thermomechanical treatment was used to enhance mechanical properties of a high-manganese austenitic steel. Simple uniaxial tension tests revealed that the treated steel exhibits an outstanding strength (yield strength: 970MPa and tensile strength: 1384MPa) and ductility (fracture strain: 37%) synergy. Microstructural studies showed that several strengthening mechanisms contribute to mechanical properties of the treated steel, including nano grains, nano twinned austenite grains, nano carbides and TRIP. Stacking fault energy and strain-induced martensitic transformation were found to have an important role in appropriate adjustment of the strengthening mechanisms to achieve the optimum properties.
Kermanpur, A.,Behjati, P.,Han, J.,Najafizadeh, A.,Lee, Y.K. Scientific and Technical Press ; Elsevier Science 2015 Materials & Design Vol.82 No.-
Deformation mechanisms of the Ni-free Fe-18Cr-12Mn-0.05C (wt%) austenitic steels containing 0, 0.25 and 0.44N were investigated. Effects of N addition, strain and temperature on the formation of deformation-induced ε- and α'-martensite phases were determined using transmission electron microscopy and electron back-scattered diffraction techniques. Based on the microstructural evolutions, it is proposed that deformation mechanism of these steels includes the sequence of γ→ε-martensite→α'-martensite, in which the formation and stability of the ε-martensite is significantly enhanced by the N content. Increased deformation temperature from 298 to 373K reduces the formation of ε-martensite (more than 80%).
Keyhani, Elahe,Muhammadnejad, Ahad,Behjati, Farkhondeh,Sirati, Fereidoon,Khodadadi, Faranak,Karimlou, Masoud,Moghaddam, Fatemeh A.,Pazhoomand, Reza Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.12
Background: Breast cancer is the most common malignancy among women in both developed and developing countries. The burden is increasing in low-income and middle-income countries (LMCs) and threatens the public health of such societies. Introduction of expensive monoclonal antibodies to cancer treatment regimens poses a real challenge in the health systems of LMCs. Despite controversy of cost-effectiveness of bevacizumab in breast cancer, some studies indicate gain of patients from this drug. The present study aimed to propose a priority setting model for administration of anti-angiogenic agents in breast cancer via assessment of tumor angiogenesis by the microvessel density (MVD) method and associations with clinicopathological characteristics (including simultaneous mutations of TP53 and HER-2 genes). Materials and Methods: Age, axillary lymph nodes status, tumor size, stage and grade, estrogen and progesterone receptors status, HER-2/neu status (by immunohistochemistry and FISH test), TP53 mutation, Ki-67 (for proliferation assay) and CD34 (for angiogenesis assay) were assessed in 111 breast cancer patients. The molecular subtype of each tumor was also determined and correlations of simultaneous mutations of HER-2 and p53 genes with angiogenesis and other clinicopathological characteristics were evaluated. Results: There were significant associations between simultaneous mutations of HER-2 and p53 genes and all other parameters except tumor size. The degree of angiogenesis in the ERBB2 subtype was greater than the others. Younger patients showed a higher angiogenesis rate rather those older than 50 years. Conclusions: Our results demonstrated that patients with simultaneous mutations of HER-2 and p53 genes, those with ERBB2 molecular subtype and also younger women (often triple negative) seem more eligible for obtaining anti-angiogenic agents. These results suggest a model for priority setting of patients with breast cancer for treatment with anti-angiogenic drugs in LMCs.
Muhammadnejad, Ahad,Keyhani, Elahe,Mortazavi, Pejman,Behjati, Farkhondeh,Haghdoost, Iraj Sohrabi Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.12
Background: Canine mammary gland tumors (CMGTs) are the most common tumor found in bitches. Changes in HER-2/neu genes in human breast cancer (HBC) lead to decrease in disease-free survival (DFS) and overall survival rate (OSR). Previous studies have demonstrated that the biological behavior of malignant mammary gland tumors (MMGTs) is similar to that of HBC. The present study aimed at evaluating the relationship between overexpression of HER-2/neu and clinicopathological features in MMGTs to represent a model of prognostic factors for HBC. Materials and Method: The clinicopathological data of 35 MMGTs were obtained. Immunohistochemical staining with HER-2, Ki-67 and CD34 markers was conducted with sections from paraffin-embedded blocks. According to standard protocols, histological type, grade, margin status, lymphovascular invasion (LVI), HER-2/neu score, proliferation rate and microvessel density (MVD) of tumors were determined and the association of HER-2/neu overexpression with these parameters was assessed statistically. Results: The IHC results showed that 12 (34.3%) cases were HER-2/neu positive. Statistical analyses indicated a significant relationship between HER-2 positivity and tumor grade (p=0.043), which also was demonstrated with cancer stage (p=0.035), tumor margin involvement (p=0.016), proliferation index (p=0.001) and MVD (p=0.001); however, there was no statistical relationship between LVI and tumor size. Overexpression of the HER-2/neu gene in MMGTs results in similar biological behavior as that of HBC; as a result, these tumors have can be considered to have important similarities in clinicopathological characteristics. Conclusions: MMGTs can be regarded as an HBC animal model. Further studies in this field would result in new treatments that could be beneficial for both dogs and humans.