Investigation on Fracture Mechanism of A356 during Thixo-Forging

2006 ◽  
Vol 116-117 ◽  
pp. 140-144 ◽  
Author(s):  
Kai Kun Wang ◽  
R. Kopp ◽  
Gerhard Hirt
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Melting Point ◽  
Fracture Mechanism ◽  
Liquid Fraction ◽  
Irregular Shape ◽  
High Melting ◽  
High Melting Point ◽  
Microstructural Changes ◽  
Transmission Electron

Transmission electron microscopy (TEM) was used to assess the microstructural changes accompanying semisolid molding of a creep resistant Mg-5%Al-2%Sr alloy. It was revealed that the processing created thixotropic morphologies with globular solids of α-Mg, having well-developed sub-structures. The quickly-solidified liquid fraction, enriched in Al and Sr, led to the formation of increased volumes of a lamellae type Al4Sr phase, surrounding the secondary α-Mg. Traces of Mg17Al12 still existed, predominantly as irregular shape compounds located mainly in grain interiors. Both the primary solid and high melting point precipitates of Mn-Al modified with Sr, acted as nucleation substrates for secondary α-Mg grains.

TEM Study of a Creep-Resistant Mg-5Al-2Sr Alloy after Semisolid Molding

2006 ◽  
Vol 116-117 ◽  
pp. 136-139
Author(s):  
Frank Czerwinski ◽  
Anna Zielinska-Lipiec
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Melting Point ◽  
Liquid Fraction ◽  
Irregular Shape ◽  
High Melting ◽  
High Melting Point ◽  
Microstructural Changes ◽  
Transmission Electron

Transmission electron microscopy (TEM) was used to assess the microstructural changes accompanying semisolid molding of a creep resistant Mg-5%Al-2%Sr alloy. It was revealed that the processing created thixotropic morphologies with globular solids of α-Mg, having well-developed sub-structures. The quickly-solidified liquid fraction, enriched in Al and Sr, led to the formation of increased volumes of a lamellae type Al4Sr phase, surrounding the secondary α-Mg. Traces of Mg17Al12 still existed, predominantly as irregular shape compounds located mainly in grain interiors. Both the primary solid and high melting point precipitates of Mn-Al modified with Sr, acted as nucleation substrates for secondary α-Mg grains.

Phenomena Associated with Oxygen in Titanium

1967 ◽  
Vol 25 ◽  
pp. 310-311
Author(s):  
E. U. Lee ◽  
P. A. Garner ◽  
J. S. Owens
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Microscope ◽  
Microstructural Changes ◽  
Electrolytic Polishing ◽  
Interstitial Impurities ◽  
Thin Foils ◽  
Transmission Electron ◽  
Iodide Titanium ◽  
Alpha Titanium

Evidence for ordering (1-6) of interstitial impurities (O and C) has been obtained in b.c.c. metals, such as niobium and tantalum. In this paper we report the atomic and microstructural changes in an oxygenated c.p.h. metal (alpha titanium) as observed by transmission electron microscopy and diffraction.Oxygen was introduced into zone-refined iodide titanium sheets of 0.005 in. thickness in an atmosphere of oxygen and argon at 650°C, homogenized at 800°C and furnace-cooled in argon. Subsequently, thin foils were prepared by electrolytic polishing and examined in a JEM-7 electron microscope, operated at 100 KV.

Development of a Double Tilt Specimen Heating Holder and its Application for the Study of Phase Transformation of Si3N4 During Sintering

1997 ◽  
Vol 3 (S2) ◽  
pp. 1085-1086
Author(s):  
T. Kamino ◽  
T. Yaguchi ◽  
M. Tomita ◽  
Y. Yasutomi ◽  
K. Hidaka
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Elevated Temperatures ◽  
Heating Element ◽  
High Melting ◽  
High Melting Point ◽  
Transmission Electron ◽  
High Resolution Tem ◽  
Metal Wires ◽  
Very High

The results of our previous studies revealed that the specimen heating holder with the heating elements of spiral shaped fine metal wires of high melting point enable us to observe high resolution transmission electron microscopy(TEM) images at elevated temperatures.In fact, the holder was applied for high resolution TEM study of a formation of SiC crystal at 1500°C and a surface reconstruction of Au deposited Si particle at 1000°C successfully. However, because the heating holder was single tilt type, there was a certain limitation in its application.In this paper, development of a double tilt specimen heating holder with a heating element of spiral shaped fine metal wire and its application for the study of microstructural changes of Si3N4 during sintering at very high temperature.Photograph of the newly developed double tilt specimen heating holder is shown in Fig. 1. The heating element is mounted on the electrically isolated tilting frame of the holder and the heating current is supplied via tilting rod which is also electrically isolated from other parts of the holder.

Transmission electron microscopy of worn zirconia surfaces

1998 ◽  
Vol 13 (2) ◽  
pp. 396-405 ◽  
Author(s):  
W. M. Rainforth ◽  
R. Stevens
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Wear Behavior ◽  
Tetragonal Zirconia ◽  
Dry Sliding Wear ◽  
Microstructural Changes ◽  
Wear Rates ◽  
Transmission Electron ◽  
Order Of Magnitude ◽  
Amorphous Surface

The dry sliding wear behavior of 3 mol% tetragonal zirconia polycrystals (3Y-TZP) and a composite containing 20 vol.% SiC whiskers have been examined by transmission electron microscopy. High wear rates for the TZP were associated with dramatic microstructural changes. The extreme outer ∼ 400 nm consisted of an amorphous surface layer containing both alumina and zirconia. Below this, the t-ZrO2 grain size was an order of magnitude smaller than in the starting material. At a depth of 1–2 μm the tetragonal grains had become elongated, with a maximum aspect ratio of 30 : 1. The first monoclinic zirconia was found at a depth of 5 μm. In contrast, the composite exhibited a wear rate 5 orders of magnitude lower, associated with minor microstructural changes.

Structural Changes in 238Pu-Substituted Zirconolite on Recovery from the Metamict State

1985 ◽  
Vol 50 ◽  
Author(s):  
F. W. Clinard ◽  
R. J. Livak ◽  
L. W. Hobbs ◽  
D. L. Rohr
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Thermal History ◽  
Structural Changes ◽  
Intermediate Stage ◽  
Irradiation Damage ◽  
Microstructural Changes ◽  
Final Value ◽  
Transmission Electron ◽  
Internal Strains

Abstract238Pu-substituted zirconolite (CaPuTi2O7) was held at ≈350 K for a time sufficient to allow self-irradiation damage to convert the material to the metamict condition. Samples were then stored at 875 K, while dimensional and microstructural changes were monitored by dilatometry and transmission electron microscopy. Densification proceeded sporadically over a period of ≈400 days, attaining a final value of 4 vol% as a result of crystallization. The material was found to be friable at an intermediate stage of recovery, apparently as a result of internal strains. Evidence is presented that CaPuTi2O7 can exist in more than one metamict state, depending on extent of prior damage and thermal history.

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