scholarly journals Microstructural Improvement of Eutectic Al + Mg2Si Phases on Al–Zn–Si–Mg Cast Alloy with TiB2 Particles Additions

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2902
Author(s):  
Byungjoo Kim ◽  
Jihoon Hwang ◽  
Yongho Park ◽  
Youngcheol Lee
Keyword(s):  
Crystal Structure ◽  
Aluminum Alloys ◽  
Heterogeneous Nucleation ◽  
Cast Alloy ◽  
Mg2si Phase ◽  
Phase Modification ◽  
Polarizing Microscope ◽  
Nucleation Sites ◽  
Tib2 Particles

In this study, the effects of adding TiB2 particles to eutectic Al + Mg2Si phases in aluminum alloys were analyzed. The eutectic Al + Mg2Si phases were modified effectively when a large amount of TiB2 was added, and changes in the shape, size, and distribution of the eutectic Al + Mg2Si phases were confirmed using a polarizing microscope and FE-SEM. The crystal structure of the TiB2 particles and Mg2Si phases were analyzed using HR-TEM, and the analysis confirmed that the TiB2 particles can act as heterogeneous nucleation sites. This paper intends to clarify the principle of phase modification of the eutectic Al + Mg2Si phases by TiB2 particles and proposes a new mechanism to improve Mg2Si phase modification when TiB2 particles are added.

scholarly journals Effect of Eutectic Mg2Si Phase Modification on the Mechanical Properties of Al-8Zn-6Si-4Mg-2Cu Cast Alloy

Metals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 32 ◽  
Author(s):  
Byung Joo Kim ◽  
Sung Su Jung ◽  
Ji Hoon Hwang ◽  
Yong Ho Park ◽  
Young Cheol Lee
Keyword(s):  
Mechanical Properties ◽  
Master Alloy ◽  
Base Alloy ◽  
Cast Alloy ◽  
Energy Dispersive Spectrometer ◽  
Chinese Script ◽  
Phase Modification ◽  
Master Alloys ◽  
Polygonal Shape ◽  
Tib2 Particles

The modification effect of Al-5Ti-1B master alloy on eutectic Mg2Si in Al-Zn-Si-Mg system alloy was investigated in this study. The microstructure shows that an extreme effect can be achieved after the addition of Al-5Ti-1B master alloy into the base alloy. The morphology of eutectic Mg2Si changed from Chinese script to fine polygonal shape, and the size was refined from over 50 μm to under 10 μm. This morphology change is believed to be due to TiB2 particles existing in Al-5Ti-1B master alloy, and the presence of TiB2 particles inside the modified Mg2Si was confirmed by scanning electron microscope/energy dispersive spectrometer (SEM/EDS) observation. The mechanical properties were also improved by the addition of Al-5Ti-1B master alloys. This study investigated the reason for the improvement in mechanical properties with the modification of the microstructure.

scholarly journals First Principle Study of TiB2 (0001)/γ-Fe (111) Interfacial Strength and Heterogeneous Nucleation

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1573
Author(s):  
Qin Wang ◽  
Peikang Bai ◽  
Zhanyong Zhao
Keyword(s):  
Stainless Steel ◽  
Heterogeneous Nucleation ◽  
316L Stainless Steel ◽  
Interfacial Strength ◽  
Interface Energy ◽  
Interface Fracture ◽  
Partial Density ◽  
Covalent Bonds ◽  
Tib2 Particles ◽  
Adhesion Work

TiB2/316L stainless steel composites were prepared by selective laser melting (SLM), and the adhesion work, interface energy and electronic structure of TiB2/γ-Fe interface in TiB2/316L stainless steel composites were investigated to explore the heterogeneous nucleation potential of γ-Fe grains on TiB2 particles using first principles. Six interface models composed of three different stacking positions and two different terminations were established. The B-terminated-top 2 site interface (“B-top 2”) was the most stable because of the largest adhesion work, smallest interfacial distances, and smallest interfacial energy. The difference charge density and partial density of states indicated that a large number of strong Fe-B covalent bonds were formed near the “B-top 2” interface, which increased the stability of interface. Fracture analysis revealed that the bonding strength of the “B-top 2” interface was higher than that of the Fe matrix, and it was difficult to fracture at the interface. The interface energy at the Ti-poor position in the “B-top 2” interface model was smaller than that of the γ-Fe/Fe melt, indicating that TiB2 had strong heterogeneous nucleation potency for γ-Fe.

Geometric Design of Heterogeneous Nucleation Sites on Biocompatible Surfaces

2013 ◽  
Vol 13 (8) ◽  
pp. 3835-3841 ◽  
Author(s):  
Vilmalí López-Mejías ◽  
Allan S. Myerson ◽  
Bernhardt L. Trout
Keyword(s):  
Heterogeneous Nucleation ◽  
Geometric Design ◽  
Nucleation Sites

Heterogeneous Formation of Oriented Silicon Oxynitride on α-Si3N4 Seed Crystals : Habits And Radiation Stability

1999 ◽  
Vol 5 (S2) ◽  
pp. 778-779
Author(s):  
R.W Carpenter ◽  
W Braue ◽  
M.J. Kim
Keyword(s):  
Silicon Nitride ◽  
Heterogeneous Nucleation ◽  
Radiation Stability ◽  
Silicon Oxynitride ◽  
Minor Constituent ◽  
Sintering Aids ◽  
Sintering Aid ◽  
Nucleation Sites ◽  
Heterogeneous Formation ◽  
A Minor

Lath-like silicon oxynitride crystals have often been observed in the microstructure of silicon nitride based ceramics after processing. They are usually located in glassy regions which are siliceous solidified sintering aid liquid, and usually contain a small (∼100nm) a-Si3N4 crystal. These nitride crystals are considered to be seeds, incompletely dissolved in the melt, that are heterogeneous nucleation sites for the oxynitride crystals. We present here the first observations of morphological and crystallographic habits between the seed nanocrystals and the host oxynitride laths.Fig. 1 shows a typical oxynitride lath containing a nitride seed crystal. The lath is surrounded by glass and ß-Si3N4 particles, and a small cristobalite particle (a minor constituent). This microstructure is from an Si02-Si3N4 ceramic processed with Al2O3 sintering aid. The same oxynitride lath/seed structures were observed when other sintering aids (eg. Y2O3, MgO, ZrO2) were used, so they are independent of sintering aid.

The Effect of the Erbium Content on the Microstructure and Mechanical Property of 6061 Aluminum Alloys

2017 ◽  
Vol 898 ◽  
pp. 35-40 ◽  
Author(s):  
Wen Jian Lv ◽  
Bo Long Li ◽  
Peng Qi ◽  
Zuo Ren Nie
Keyword(s):  
Solid Solution ◽  
Grain Size ◽  
Tensile Strength ◽  
Aluminum Alloys ◽  
Cast Alloy ◽  
Solution Treatment ◽  
Size Refinement ◽  
Effective Grain Size ◽  
Different Content ◽  
Microstructure And Mechanical Property

The 6061 aluminum alloys with different content of erbium were prepared. The erbium content was optimized by measurement of grain refining effects and tensile strength. After solid solution treatment of the alloy with optimized erbium content at 505 °C ~ 595 °C for 4 h. and then ageing at –160 °C ~ 200 °C for 3 h., the grain size decreased with the content of erbium, achieving the most effective grain size refinement at the erbium content of 0.15wt.%. The tensile strength of as-cast alloy could reach up to 243 MPa at the erbium content of 0.15%. -Combined with the microstructures and mechanical properties, the erbium content of 0.15% was the optimized content, and heat treatments of ageing at 180 °C for 3 h. followed by solid solution at 565 °C for 4 h were suggested.

scholarly journals Fracture–Mechanical Assessment of the Effect of Defects on the Fatigue Lifetime and Limit in Cast and Additively Manufactured Aluminum–Silicon Alloys from HCF to VHCF Regime

Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 943 ◽  
Author(s):  
Jochen Tenkamp ◽  
Mustafa Awd ◽  
Shafaqat Siddique ◽  
Peter Starke ◽  
Frank Walther
Keyword(s):  
Stress Intensity ◽  
Aluminum Alloys ◽  
Cast Alloy ◽  
Weight Ratio ◽  
Silicon Alloys ◽  
Fatigue Lifetime ◽  
Aluminum Silicon Alloys ◽  
Die Cast ◽  
The Relationship ◽  
Aluminum Silicon

Aluminum–silicon alloys are commonly used in die-cast and additively manufactured (AM) light-weight components due to their good processability and high strength-to-weight ratio. As both processing routes lead to the formation of defects such as gas and shrinkage porosity, a defect-sensitive design of components is necessary for safe application. This study deals with the fatigue and crack propagation behavior of die-cast alloy AlSi7Mg0.3 and additively manufactured alloy AlSi12 and its relation to process-induced defects. The different porosities result in significant changes in the fatigue stress-lifetime (S–N) curves. Therefore, the local stress intensity factors of crack-initiating defects were determined in the high and very high cycle fatigue regime according to the fracture mechanics approach of Murakami. Through correlation with fatigue lifetime, the relationship of stress intensity factor (SIF) and fatigue lifetime (N) could be described by one power law (SIF–N curve) for all porosities. The relationship between fatigue limit and defect size was further investigated by Kitagawa–Takahashi (KT) diagrams. By using El Haddad’s intrinsic crack length, reliable differentiation between fracture and run out of the cast and AM aluminum alloys could be realized. SIF–N curves and KT diagrams enable a reliable fatigue design of cast and AM aluminum alloys for a finite and infinite lifetime.

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