scholarly journals Failure Analysis of Rheocast Cylinder Head Covers of Hypereutectic Al–Si Alloys

2020 ◽  
Author(s):  
Jian Feng
Keyword(s):  
Heat Treatment ◽  
Surface Morphology ◽  
Service Time ◽  
Shot Peening ◽  
High Frequency ◽  
Cylinder Head ◽  
Die Casting ◽  
Fatigue Properties ◽  
Homogeneous Distribution ◽  
Engine Components

AbstractThe purpose of the present study is to determine the cause of failures of semisolid rheocast cylinder head covers of hypereutectic modified LM30 alloys. The covers, manufactured by rheocasting, a process that consists of the incorporation and homogeneous distribution of the reinforcements in semisolid metal (SSM) before die casting, were shot-peened after heat treatment to increase the fatigue resistance. However, these engine components failed during operation after a short service time. The major flaws were located by radiography. The microstructure was controlled by metallography. Significant interactions between shot peening and surface/subsurface contaminants were identified by surface morphology and fractography. The fatigue properties of hypereutectic alloys were investigated by a high-frequency vibrophore. It was identified that the failure was related to the cleanliness of SSM as well as the rheocasting process. Recommendations were given to prevent the recurrence of similar failures.

Effect of Shot Peening on the Long Life Fatigue Properties of Ti6Al4V with Different Heat Treatment

2015 ◽  
Vol 664 ◽  
pp. 81-86 ◽  
Author(s):  
X.J. Cao ◽  
Luo Peng Xu ◽  
Chong Wang ◽  
Jiang Jin ◽  
Qing Yuan Wang
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Shot Peening ◽  
Oxide Inclusion ◽  
Surface Hardness ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Almen Intensity ◽  
Ultrasonic Fatigue ◽  
Long Life

In order to investigate the effect of shot peening on the long life fatigue properties of Ti6Al4V (TC4), ultrasonic fatigue tests were performed with a frequency of 20 kHz. According to different heat treatment, two groups of specimens were surface modified by shot peening with an Almen intensity of 0.10 mmA~ 0.15 mmA and an overlapping rate of 100%. One group was stress-relief annealed at 650 °C, and the other was then treated with solution-aging. With the shot peening, both the depth of the residual stress layer and the maximum compressive residual stress are increased. Surface hardness is also increased. The fatigue strength is increased, but enhancement is no more than 5% because of the increase of surface roughness. Noticeably, all of the TC4 specimens after shot peening show inner crack initiations. Oxide inclusion is always the core of cracks, and the small crack propagation in crack initiation area acts as the slip of α-phase.

Improvement of Fatigue Properties of Fillet Lap Joints by Applying. Local Heat Treatment with TIG Arc.

1999 ◽  
Vol 17 (2) ◽  
pp. 319-325 ◽  
Author(s):  
Koichi OSAWA ◽  
Tsuyoshi SHIOZAKI ◽  
Toshiaki URABE ◽  
Akihide YOSHITAKE ◽  
Takanobu SAITO ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Local Heat ◽  
Lap Joints ◽  
Fatigue Properties ◽  
Local Heat Treatment

scholarly journals Grain Size Evolution and Mechanical Properties of Nb, V–Nb, and Ti–Nb Boron Type S1100QL Steels

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 492
Author(s):  
Jan Foder ◽  
Jaka Burja ◽  
Grega Klančnik
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Grain Size ◽  
Hot Forging ◽  
Size Control ◽  
High Strength ◽  
Fatigue Properties ◽  
Titanium Addition ◽  
Austenite Grain Size ◽  
Size Evolution

Titanium additions are often used for boron factor and primary austenite grain size control in boron high- and ultra-high-strength alloys. Due to the risk of formation of coarse TiN during solidification the addition of titanium is limited in respect to nitrogen. The risk of coarse nitrides working as non-metallic inclusions formed in the last solidification front can degrade fatigue properties and weldability of the final product. In the presented study three microalloying systems with minor additions were tested, two without any titanium addition, to evaluate grain size evolution and mechanical properties with pre-defined as-cast, hot forging, hot rolling, and off-line heat-treatment strategy to meet demands for S1100QL steel. Microstructure evolution from hot-forged to final martensitic microstructure was observed, continuous cooling transformation diagrams of non-deformed austenite were constructed for off-line heat treatment, and the mechanical properties of Nb and V–Nb were compared to Ti–Nb microalloying system with a limited titanium addition. Using the parameters in the laboratory environment all three micro-alloying systems can provide needed mechanical properties, especially the Ti–Nb system can be successfully replaced with V–Nb having the highest response in tensile properties and still obtaining satisfying toughness of 27 J at –40 °C using Charpy V-notch samples.

scholarly journals Low Cycle Fatigue Characteristics of Oxygen-Free Copper for Electric Power Equipment

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4237
Author(s):  
Takuma Tanaka ◽  
Togo Sugioka ◽  
Tatsuya Kobayashi ◽  
Ikuo Shohji ◽  
Yuya Shimada ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Electric Power ◽  
Stress Amplitude ◽  
Low Cycle Fatigue ◽  
Ebsd Analysis ◽  
Fatigue Properties ◽  
Power Equipment ◽  
Cycle Fatigue ◽  
Fracture Surfaces ◽  
Heat Treated

The effect of heat treatment on tensile and low cycle fatigue properties of the oxygen-free copper for electric power equipment was investigated. The heat treatment at 850 °C for 20 min, which corresponds to the vacuum brazing process, caused the grain growth and relaxation of strain by recrystallization, and thus, the residual stress in the oxygen-free copper was reduced. The tensile strength and 0.2% proof stress were decreased, and elongation was increased by the heat treatment accompanying recrystallization. The plastic strain in the heat-treated specimen was increased compared with that in the untreated specimen under the same stress amplitude condition, and thus, the low cycle fatigue life of the oxygen-free copper was degraded by the heat treatment. Striation was observed in the crack initiation area of the fractured surface in the case of the stress amplitude less than 100 MPa regardless of the presence of the heat treatment. With an increase in the stress amplitude, the river pattern and the quasicleavage fracture were mainly observed in the fracture surfaces of the untreated specimens, and they were observed with striations in the fracture surfaces of the heat-treated ones. The result of the electron backscattered diffraction (EBSD) analysis showed that the grain reference orientation deviation (GROD) map was confirmed to be effective to investigate the fatigue damage degree in the grain by low cycle fatigue. In addition, the EBSD analysis revealed that the grains were deformed, and the GROD value reached approximately 28° in the fractured areas of heat-treated specimens after the low cycle fatigue test.

scholarly journals Influence of V and Heat Treatment on Characteristics of WMoNbTaV Refractory High-Entropy Alloy Coatings by Mechanical Alloying

Coatings ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 265
Author(s):  
Chun-Liang Chen ◽  
Sutrisna
Keyword(s):  
Heat Treatment ◽  
Mechanical Alloying ◽  
Annealing Treatment ◽  
High Energy ◽  
304 Stainless Steel ◽  
Homogeneous Distribution ◽  
High Entropy Alloy ◽  
Solid Solution Phase ◽  
High Entropy ◽  
Steel Substrates

Refractory high-entropy alloy (RHEA) is one of the most promising materials for use in high-temperature structural materials. In this study, the WMoNbTaV coatings on 304 stainless steel substrates has been prepared by mechanical alloying (MA). Effects of V addition and subsequent heat treatment on properties of the WMoNbTaV coatings were investigated. The results show that the RHEA coatings with nanocrystalline body-centered cubic (BCC) solid-solution phase were generated by the mechanical alloying process. The presence of the V element promotes a uniform microstructure and homogeneous distribution of composition in the RHEA coatings due to improving alloying efficiency, resulting in an increase of hardness. After the annealing treatment of the RHEA coatings, microstructure homogeneity was further enhanced; however, the high affinity of Ta for oxygen causes the formation of Ta-rich oxides. Annealing also removes strain hardening generated by high-energy ball milling and thus decreases the hardness of the RHEA coating and alters microstructure evolution and mechanical properties.

Effect of Heat Treatment on Very High Cycle Fatigue Properties of TC4

2021 ◽  
Vol 881 ◽  
pp. 3-11
Author(s):  
Bo Han Wang ◽  
Li Cheng ◽  
Xun Chun Bao
Keyword(s):  
Heat Treatment ◽  
High Cycle Fatigue ◽  
Treatment Method ◽  
Fatigue Performance ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Α Phase ◽  
Very High Cycle Fatigue ◽  
Significant Difference ◽  
Very High

The bimodal, equiaxed and Widmanstatten microstructures of TC4 titanium alloy were obtained through different heat treatment processes. The content of primary α phase in the bimodal and equiaxed microstructures was measured to be about 40% and 90%, and the average size was about 9.4μm and 7.9 μm. Three types of microstructure fatigue S-N curves are obtained, which are successively descending type, single-platform descending type and infinite life type. The order of very high cycle fatigue performance is Widmanstatten>equiaxed>bimodal, but the anti-fretting fatigue performance of Widmanstatten is the worst. The grain refinement makes the fatigue performance of the equiaxed better than that of the bimodal. The second process is determined as the best heat treatment method. There is no significant difference in the life of the crack propagation stage. The very high cycle fatigue life mainly depends on the crack initiation stage. In the bimodal and the equiaxed, the crack initiates in the primary α phase of the subsurface, and the crack in the Widmanstatten initiates in the coarse α 'grain boundary of the subsurface.

Characterization of nanocrystalline surface layer induced by shot peening and effect on their fatigue strength.

2004 ◽  
Vol 843 ◽  
Author(s):  
Hideo Mano ◽  
Kondo Satoru ◽  
Akihito Matsumuro ◽  
Toru Imura
Keyword(s):  
Residual Stress ◽  
Surface Layer ◽  
Fatigue Strength ◽  
Vickers Hardness ◽  
Shot Peening ◽  
White Layer ◽  
The Other ◽  
Fatigue Properties ◽  
Nanocrystalline Layer

ABSTRACTThe shot peening process is known to produce a hard layer, known as the white layer” on the surface of coil springs. However, little is known about the fatigue properties of this white-layer.In this study, coil springs with a white-layer were manufactured. The surface of these springs was then examined using micro Vickers hardness, FE-SEM etc. to test fatigue strength of the springs.From the results obtained, a microstructure of the white-layer with grain size of 50–100 nm was observed, with a Vickers hardness rating of 8–10 GPa.Tow category springs were manufactured utilizing a double-peening process. These springs had the same residual stress destruction and surface roughness. Only one difference was observed: one spring had a nanocrystalline layer on the surface, while the other did not. The results of the fatigue test realized an increase in the fatigue life of the nanocrystalline surface layer by 9%.

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