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Determination of Phase Transformation for TC21 ti-alloy by Dilatometry Method

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Open Journal of Metal 2019年第1期9卷 1-10页

作者： Ramadan N. Elshaer Khaled M. Ibrahim Azza F. Barakat Ahmed I. Farahat Reham R. Abbas Tabbin Institute for Metallurgical Studies Cairo Egypt Central Metallurgical R & D Institute Cairo Egypt Faculty of Engineering Helwan University Cairo Egypt Faculty of Engineering Suez University Suez Egypt

The α + β ? β phase transformation kinetics of TC21 ti-alloy during continuous heating and cooling were studied using a dilatometric technique. Dilatometric heating curve exhibited that two characteristic reflection points can be observed with increasing the heating temperature. Ts referred to the initial transformation temperature of α + β → β and Tf referred to the final transformation temperature of α + β → β. Ts was reported at 720°C, whereas the corresponding Tf was obtained at 950°C. The initial and final transforming temperatures by the first derivative curve were reported at 730°C and 955°C, respectively, which are close to the values obtained in the dilatometric heating curve. Dilatometric cooling curve showed that the starting temperature of β → β + α phase transformation was 880°C;however, the corresponding finishing temperature was 670°C. The starting and finishing temperatures using the first derivative curve were obtained at 665°C and 885°C, respectively. The first derivative for the studied dilatometric heating and cooling curves showed that the starting and finishing temperatures of α + β ? β phase transformation were more accurate and objective. Results show the α + β → β transformation heating curve exhibits a typical S-shaped pattern.

关键词： TC21 ti-alloy Phase Transformation Dilatometry Heating Cooling

Fatigue Performance of Heat Treated TC21 ti-alloy

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Open Journal of Metal 2019年第2期9卷 11-18页

作者： Ramadan N. Elshaer Khaled M. Ibrahim Azza F. Barakat Reham R. Abbas Tabbin Institute for Metallurgical Studies Cairo Egypt Central Metallurgical R & D Institute Cairo Egypt Faculty of Engineering Helwan University Cairo Egypt Faculty of Engineering Suez University Suez Egypt

TC21 is considered a new titanium alloy that is used in aircraft applications as a replacement for the famous ti-6Al-4V alloy due to its high strength. The effect of single and duplex stage heat treatments on fatigue behavior of TC21 ti-alloy (ti-6Al-2Sn-2Zr-3Mo-1Cr-2Nb-0.09Si, wt.%) was investigated. Two heat treatment cycles were applied on as-received TC21 ti-alloy. The first cycle was called single stage heat treatment (SSHT). The other cycle was named duplex stage heat treatment (DSHT). Typical microstructures of SSHT & DSHT composed of primary equiaxed α phase, residual β phase and secondary α phase (αs). Secondary α phase was precipitated in the residual β phase due to low cooling rate using air cooling and aging treatment. Morphology of α phase does not change after solution treatments, while their volume fraction and grain size were changed. SSHT showed the highest fatigue strength of 868 MPa due to high tensile strength, hardness and existing of high percentages of residual β phase in the microstructure. However, DSHT reported lower fatigue strength of 743 MPa due to increasing grain size of α phase. The fracture surface of fatigue samples showed cleavage ductile fracture mode for both heat treatment cycles.

关键词： TC21 ti-alloy Solution Treatment Microstructure Hardness Tensile Fatigue

Microstructural Evolution of Localized Shear Bands Induced during Explosion in ti-6Al-4V alloy

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Journal of Materials Science & Technology 2003年第5期19卷 385-387页

作者： YongboXU M.A.Mevers ShenyangNationalLaboratoryforMaterialsScience InstituteofMetalResearchChineseAcademyofSciencesShenvang110016China DepartmentofMechanicalandAerospaceEngineering UniversityofCaliforniaSanDiegoLaJollaCA920930-0411USA

Microstructures of the localized shear bands generated during explosion with a thick-walled cylinder specimen in ti-6AI-4V alloy, were characterized by TEM and SEM. The results show that the twinning is a major mode of deformation, and the distortion-free grains in the bands with the size of 10μm in diameter were proposed to be the re-crystallization during dynamic explosion. The further observations show that the α→α2 phase transformation may occur in the bands, and this kind of transformation could be confirmed by its dark field image and electron diffraction analysis. Analysis shows that there is specified orientation between the α and α2 Phases.

关键词： Shear localization ti-alloy Phase-transformation Twinning

Fretting Fatigue Improvement of ti6Al4V by Coating and Shot Peening

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Journal of Materials Science & Technology 2005年第2期21卷 246-250页

作者： DaoxinLIU XiaodongZHU BinTANG JiawenHE NorthwesternPolytechnicalUniversity Xi'an710072China Xi'anJiaotongUniversity Xi’an710049China TaiyuanUniversityofTechnology Taiyuan030024China

Ion beam enhanced deposition (IBED) was employed to increase the fretting fatigue resistance of ti6AI4V. CrN and tiN hard coatings were applied on the base material and shot peening was combined with the hard coatings to study the duplex effect on fretting fatigue resistance. The IBED coatings exhibited a good bonding strength. They did not spall off even after shot peening. However, an optimum composition of CrN showed better fretting fatigue resistance than that of tiN with the same processing parameters.

关键词： Fretting fatigue ti-alloy Shot peening Coatings

Effect of Heat Treatment Processes on Microstructure and Mechanical Behavior of TC21 titanium alloy

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Open Journal of Metal 2017年第3期7卷 39-57页

作者： Ramadan N. Elshaer Khaled M. Ibrahim Azza F. Barakat Reham R. Abbas Central Metallurgical R & D Institute Cairo Egypt College of Engineering Taibah University Medina KSA Faculty of Engineering Helwan University Cairo Egypt

The effect of heat treatment on microstructure and tensile properties as well as wear behavior on TC21 (ti-6Al-2Sn-2Zr-3Mo-1Cr-2Nb-Si, wt.%) ti-alloy was investigated. The samples were solution treated at 900°C for 15 min followed by furnace cooling to 800°C with a cooling rate 1°C/min and holding for 20 min, then the samples cooled down to room temperature either using water quenching (WQ) or air cooling (AC). Consequently, aging treatment was applied at 575°C for 4 hr. The microstructure feature showed a secondary α phase (αs) precipitated in residual β phase due to the step cooling from 900°C to 800°C inside furnace as well as the aging treatment. The highest wear rate was obtained for WQ samples due to increasing in volume fraction of αp (58%). However, the lowest wear rate was reported for WQ + Aging samples due to the high hardness. Optimum mechanical properties of the studied TC21 ti-alloy were obtained for AC + Aging condition. A better combination of hardness, tensile properties, and wear resistance was achieved for AC + Aging samples, although their wear resistance was found to be slightly lower than that of WQ + Aging samples.

关键词： TC21 ti-alloy Cooling Rate Aging Microstructure Tensile Properties Wear

Study on J-integral with SENB specimens in a condenser material

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Journal of Marine Science and Application 2004年第1期3卷 91-94页

作者： RENZheng-yi GUOEr-jun LIQing-fen SchoolofMechanical＆ElectricalEngineering HarbinEngineeringUniversityHarbin150001China

A series of tests was performed with three-point single-edge-notched-bend (SENB) specimens in a condenser material (titanium alloy). Results show that the J-integral values of welded joint and HAZ are obviously smaller than those of the base metal. It signifies that the welding process can result in a reduced toughness of titanium alloy and the effect of crack orientation on toughness value is not negligible for engineering applications. Besides, the J-integral values of L-T direction specimens are much higher than those of L-S ones. The J-integral values of rolled ring are:JC-R>JC-L>JL-R.

关键词： condenser material ti-alloy J-integral welding process crack orientation