The Room Temperature and Elevated Temperature Fracture Toughness Response of Alloy A-286

1978 ◽  
Vol 100 (2) ◽  
pp. 195-199 ◽  
Author(s):  
W. J. Mills
Keyword(s):  
Fracture Toughness ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Second Phase ◽  
Surface Micromorphology ◽  
Second Phase Particles ◽  
The Matrix ◽  
Temperature Fracture ◽  
Increasing Temperature ◽  
Base Superalloy

The elastic-plastic fracture toughness (JIc) response of precipitation strengthened Alloy A-286 has been evaluated by the multi-specimen R-curve technique at room temperature, 700 K (800°F) and 811 K (1000°F). The fracture toughness of this iron-base superalloy was found to decrease with increasing temperature. This phenomenon was attributed to a reduction in the materials’s strength and ductility at elevated temperatures. Electron fractographic examination revealed that the overall fracture surface micromorphology, a duplex dimple structure coupled with stringer troughs, was independent of test temperature. In addition, the fracture resistance of Alloy A-286 was found to be weakened by the presence of a nonuniform distribution of second phase particles throughout the matrix.

Temperature Dependence of Fracture Toughness of the Cubic (L12) Titanium Trialuminides

1996 ◽  
Vol 460 ◽  
Author(s):  
R. A. Varin ◽  
L. Zbroniec
Keyword(s):  
Fracture Toughness ◽  
Stress Intensity Factor ◽  
Room Temperature ◽  
Maximum Load ◽  
Gradual Transition ◽  
Transgranular Cleavage ◽  
Temperature Range ◽  
Temperature Fracture ◽  
Increasing Temperature ◽  
Work Of Fracture

ABSTRACTFracture toughness vs. temperature of the cubic (L12), Mn- modified titanium trialuminide (based on Al3Ti) was investigated in air at the temperature range up to 1000°C. Toughness calculated from the maximum load exhibits a broad peak (KQ≈7–10 MPara0,5) at the 200- 500°C temperature range and then decreases with increasing temperature, reaching a room temperature value of ∼4.5 MPam0.5 at 1000°C. However, the work of fracture (γWOF, J/m2) and the stress intensity factor calculated from it (KIWOF) increases continuously with increasing temperature. Fracture modes exhibit a gradual transition from transgranular cleavage at room temperature to predominantly intergranular failure at the 800- 1000°C range.

Annealing Effects on Toughened Intra-Type Nanocomposites

2006 ◽  
Vol 45 ◽  
pp. 1632-1639 ◽  
Author(s):  
Hideo Awaji ◽  
Seong Min Choi
Keyword(s):  
Fracture Toughness ◽  
Elevated Temperatures ◽  
Volume Fraction ◽  
Process Zone ◽  
Nitrate Solution ◽  
Crack Tip ◽  
Hydrogen Atmosphere ◽  
Second Phase ◽  
High Porosity ◽  
The Matrix

Intra-type nanocomposites, in which nanosized second-phase particles are embedded within matrix grains, generate dislocations around the dispersed nanoparticles. The intra-type nanostructure induces a thermal expansion mismatch between the matrix and the dispersed particles, which will yield nanoscale stress distribution around the particles and generate lattice defects, such as dislocations. The dislocations of ceramics can be generated at elevated temperatures, become sessile dislocations at room temperature, and serve as nanocrack nuclei in highly stresses fields, e.g. at a main crack tip. The frontal process zone size ahead of a crack tip is expanded due to creation of nanocracks and hence the fracture toughness is improved. Annealing after sintered nanocomposites is important in controlling the dislocation activities. Appropriate annealing will disperse dislocations into the matrix grains. However, dislocations are sensitive to temperature, and higher temperature or longer annealing time result in dislocation disappearance and cause the reduction of the strength and fracture toughness of nanocomposites. In this study, commercially available γ-alumina agglomerated powder with high porosity was used to create the intra-type nanostructure. Nickel nitrate solution was infiltrated into nanopores of the γ-alumina agglomerates in vacuum. The alumina/nickel composite powder following reduction in hydrogen atmosphere was sintered using a pulse electric current sintering method. The volume fraction of nickel was about 3 vol %. After appropriate annealing, the highest fracture toughness was obtained to be 7.6 MPam1/2, which is two times higher than that of monolithic alumina.

Microstructural Evolution and Room Temperature Fracture Toughness of a Nb-Ti-Si-Cr-Al-Hf-Y Alloy Prepared by Directional Solidification

2019 ◽  
Vol 971 ◽  
pp. 59-64
Author(s):  
Guan Qun Zhuo ◽  
Lin Fen Su ◽  
Kai Yong Jiang
Keyword(s):  
Heat Treatment ◽  
Fracture Toughness ◽  
Directional Solidification ◽  
Microstructural Evolution ◽  
Room Temperature ◽  
Growth Direction ◽  
Withdrawal Rate ◽  
The Matrix ◽  
Temperature Fracture

The Nb-24Ti-12Si-14Cr-2Al-2Hf-0.1Y (at.%) alloys were fabricated by directional solidification with selected withdrawal rate 1.2 and 18 mm/min, followed by a heat treatment at 1375 °C for 10 h. The microstructure of directional solidified samples were composed of NbSS, Cr2Nb and eutectics (NbSS+Nb5Si3), aligning with the growth direction. After heat treatment, the NbSS in the eutectic structures and NbSS dendrites were connected to form the matrix, and the silicide and Cr2Nb tended to spheroidize. The sample prepared by higher withdrawal rate plus heat treament shows higher average KQ values. The results suggested that the Nb-Si based alloy showed higher room-temperature fracture toughness when the microstructure consists of continuous NbSS distributed with finer Nb5Si3 and Cr2Nb.

Particle-Stimulated Nucleation of Dynamic Recrystallization in AZ31 Alloy at Elevated Temperatures

2005 ◽  
Vol 488-489 ◽  
pp. 261-264 ◽  
Author(s):  
Lan Jiang ◽  
Guang Jie Huang ◽  
Stéphane Godet ◽  
John J. Jonas ◽  
Alan A. Luo
Keyword(s):  
Magnesium Alloy ◽  
Elevated Temperatures ◽  
Az31 Alloy ◽  
Coarse Grained ◽  
Second Phase ◽  
Compression Tests ◽  
Second Phase Particles ◽  
The Matrix ◽  
Second Phases ◽  
Cast Magnesium

Particle-stimulated nucleation (PSN) was investigated in magnesium alloy AZ31 to study the effect of the evolution of second-phases during extrusion and other metal forming processes. Compression tests were carried out on samples taken from coarse-grained as-cast magnesium alloy billets containing a lamellar Mg17All2 eutectic phase and (Al, Mn) particles. These revealed that particle-stimulated DRX nucleation (PSN) was taking place during hot deformation and that this is facilitated by the fragmentation of the Mg17All2. When Mg17All2 dissolves into the matrix at about 350°C, the (Al, Mn) particles remain effective in producing PSN at temperatures up to at least 400°C. This suggests that alloy design leading to a suitable distribution of second-phase particles can improve the properties and formability of wrought magnesium alloys.

Polishing process effect on the image of dispersed precipitates

1984 ◽  
Vol 42 ◽  
pp. 534-535
Author(s):  
C.T. Hu ◽  
C.W. Allen
Keyword(s):  
Matrix Material ◽  
Specimen Preparation ◽  
Second Phase ◽  
Precipitate Particle ◽  
Polishing Process ◽  
Second Phase Particles ◽  
The Matrix ◽  
Surface Profiles ◽  
Thinning Process

One important problem in determination of precipitate particle size is the effect of preferential thinning during TEM specimen preparation. Figure 1a schematically represents the original polydispersed Ni3Al precipitates in the Ni rich matrix. The three possible type surface profiles of TEM specimens, which result after electrolytic thinning process are illustrated in Figure 1b. c. & d. These various surface profiles could be produced by using different polishing electrolytes and conditions (i.e. temperature and electric current). The matrix-preferential-etching process causes the matrix material to be attacked much more rapidly than the second phase particles. Figure 1b indicated the result. The nonpreferential and precipitate-preferential-etching results are shown in Figures 1c and 1d respectively.

Recrystallization in Ultra-Fine Grain Structures of AA3104 Alloy Processed by ECAP and HPT

2012 ◽  
Vol 715-716 ◽  
pp. 346-353
Author(s):  
H. Paul ◽  
T. Baudin ◽  
K. Kudłacz ◽  
A. Morawiec
Keyword(s):  
High Pressure Torsion ◽  
Deformation Mode ◽  
Second Phase ◽  
Orientation Measurement ◽  
Angular Pressing ◽  
Second Phase Particles ◽  
Average Grain Size ◽  
The Matrix ◽  
Electron Microscopes ◽  
Different Strains

The objective of this study was to determine the effect of deformation mode on recrystallization behavior of severely deformed material. Commercial purity AA3104 aluminum alloy was deformed via high pressure torsion and equal channel angular pressing to different strains and then annealed to obtain the state of partial recrystallization. The microstructure and the crystallographic texture were analysed using scanning and transmission electron microscopes equipped with orientation measurement facilities. The nucleation of new grains was observed in bulk recrystallized samples and during in-situ recrystallization in the transmission microscope. Irrespective of the applied deformation mode, a large non-deformable second phase particles strongly influenced strengthening of the matrix through deformation zones around them. It is known that relatively high stored energy stimulates the nucleation of new grains during the recrystalization. In most of the observed cases, the growth of recrystallized grains occurred by the coalescence of neighboring subcells. This process usually led to nearly homogeneous equiaxed grains of similar size. The diameter of grains in the vicinity of large second phase particles was only occasionally significantly larger than the average grain size. Large grains were most often observed in places far from the particles. TEM orientation mapping from highly deformed zones around particles showed that orientations of new grains were not random and only strictly defined groups of orientations were observed.

Dependence of fracture toughness on multiscale second phase particles in high strength Al alloys

2003 ◽  
Vol 19 (7) ◽  
pp. 887-896 ◽  
Author(s):  
G. Liu ◽  
G.-J. Zhang ◽  
X.-D. Ding ◽  
J. Sun ◽  
K.-H. Chen
Keyword(s):  
Fracture Toughness ◽  
High Strength ◽  
Al Alloys ◽  
Second Phase ◽  
Second Phase Particles

scholarly journals Effect of Microstructural Continuity on Room-Temperature Fracture Toughness of ZrC-Added Mo–Si–B Alloys

2018 ◽  
Vol 59 (4) ◽  
pp. 518-527 ◽  
Author(s):  
Shunichi Nakayama ◽  
Nobuaki Sekido ◽  
Sojiro Uemura ◽  
Sadahiro Tsurekawa ◽  
Kyosuke Yoshimi
Keyword(s):  
Fracture Toughness ◽  
Room Temperature ◽  
Temperature Fracture

Microstructure of Friction Stir Processed Mg-Y-Zn Alloy

2007 ◽  
Vol 558-559 ◽  
pp. 777-780 ◽  
Author(s):  
Taiki Morishige ◽  
Masato Tsujikawa ◽  
Sung Wook Chung ◽  
Sachio Oki ◽  
Kenji Higashi
Keyword(s):  
Equal Channel Angular Extrusion ◽  
Second Phase ◽  
Ingot Metallurgy ◽  
Friction Stir ◽  
Fine Grained ◽  
Probe Diameter ◽  
Fine Grain ◽  
Second Phase Particles ◽  
The Matrix ◽  
Zn Alloy

Friction stir processing (FSP) is the effective method of the grain refinement for light metals. The aim of this study is to acquire the fine grained bulk Mg-Y-Zn alloy by ingot metallurgy route much lower in cost. Such bulk alloy can be formed by the superplastic forging. The microstructure of as-cast Mg-Y-Zn alloy was dendrite. The dendrite arm spacing was 72.5 [(m], and there are the lamellar structures in it. FSP was conducted on allover the plate of Mg-Y-Zn alloy for both surfaces by the rotational tool with FSW machine. The stirring passes were shifted half of the probe diameter every execution. The dendrite structures disappeared after FSP, but the lamellar structure could be observed by TEM. The matrix became recrystallized fine grain, and interdendritic second phase particles were dispersed in the grain boundaries. By using FSP, cast Mg-Y-Zn alloy could have fine-grained. This result compared to this material produced by equal channel angular extrusion (ECAE) or rapid-solidified powder metallurgy (RS P/M). As the result, as-FSPed material has the higher hardness than materials produced by the other processes at the similar grain size.

The Reactivity of CaTi4(PO4)6 with Alumina and Y-TZP Ceramics

2007 ◽  
Vol 361-363 ◽  
pp. 787-790
Author(s):  
Sabina Beranič Klopčič ◽  
Irena Pribošič ◽  
Tomaž Kosmač ◽  
Ute Ploska ◽  
Georg Berger
Keyword(s):  
Room Temperature ◽  
Xrd Analysis ◽  
Second Phase ◽  
Reaction Products ◽  
Stabilized Zirconia ◽  
Monoclinic Zro2 ◽  
Commercial Alumina ◽  
The Matrix ◽  
Different Temperatures ◽  
Edx Analyses

The reactivity of CaTi4(PO4)6 (CTP) with alumina and yttria-stabilized zirconia (Y-TZP) ceramics was studied. CTP powder was synthesized and composites with commercial alumina or zirconia matrices containing 10 wt% of CTP were prepared. They were sintered at different temperatures and characterized using XRD, SEM, and EDX analyses. The results showed that the alumina/CTP and Y-TZP/CTP composites start to react below 1000 °C. In the alumina/CTP composite the first reaction product, detected at 970 °C, was AlPO4. At temperatures above 1280 °C TiO2 and CaTiO3 were also formed and no CTP peaks could be detected using XRD analysis. The composite sintered at 1500 °C consisted of Al2O3 matrix, AlPO4, TiO2, CaTiO3 and Al2TiO5. The reaction products formed in the Y-TZP/CTP composite at 970 °C were TiO2 and Ca2Zr7O16. At higher sintering temperatures, 1280 °C and above, CTP was no longer present, Ca2Zr7O16 decomposed, forming CaO2 and ZrO2, and Y2O3 was consumed to form YPO4. Consequently, upon cooling to room temperature the matrix phase transformed to monoclinic ZrO2. Based on these results it can be concluded that CTP is not a suitable bioactive second phase for the fabrication of CTP composites with alumina or zirconia matrices.

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