scholarly journals Influence of Multi-Holes on Fatigue Behaviors of Cast Magnesium Alloys Based on In-Situ Scanning Electron Microscope Technology

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1700 ◽  
Author(s):  
Xi-Shu Wang ◽  
Chang-Hao Tan ◽  
Juan Ma ◽  
Xiao-Dong Zhu ◽  
Qing-Yuan Wang
Keyword(s):  
Fatigue Crack ◽  
Electron Microscope ◽  
Crack Initiation ◽  
Scanning Electron Microscope ◽  
Magnesium Alloys ◽  
Mg17al12 Phase ◽  
Cast Magnesium Alloys ◽  
Cast Magnesium ◽  
Scanning Electron

The low cycle fatigue tests on the crack initiation and propagation of cast magnesium alloys with two small holes were carried out by using in-situ scanning electron microscope (SEM) observation technology. The fatigue crack propagation behaviors and fatigue life, which are affected by two small artificial through holes, including the distances between two holes and their locations, were discussed in detail based on the experimental results and the finite element analysis (FEA). The results indicated that the fatigue multi-cracks occurred chiefly at the edges of two holes and the main crack propagation was along the weak dendrite boundary with the plastic deformation vestiges on the surface of α-Mg phase of cast AM50 and AM60B alloys. The fatigue cracking characteristics of cast AZ91 alloy depended mainly on the brittle properties of β-Mg17Al12 phase, in which the multi-cracks occurred still at the edges of two holes and boundaries of β-Mg17Al12 phase. The fatigue crack initiation position of cast magnesium alloys depends strongly on the radius of curvature of through hole or stress concentration factor at the closed edges of two through holes. In addition, the fatigue multi-cracks were amalgamated for the samples with titled 45° of two small holes of cast Mg-Al alloys when the hole distance is less than 4D (D is the diameter of the small hole).

SEM In Situ Investigation of the Effects of Ca and Sr Additions on Cracking in Cast AZ91D Alloys at Different Temperatures

2007 ◽  
Vol 353-358 ◽  
pp. 2123-2126 ◽  
Author(s):  
Xi Shu Wang ◽  
Bin Tang ◽  
Jun Chen
Keyword(s):  
Magnesium Alloys ◽  
Sem Images ◽  
Ca Addition ◽  
Mg17al12 Phase ◽  
In Situ Investigation ◽  
Different Temperatures ◽  
Cast Magnesium Alloys ◽  
Cast Magnesium ◽  
Cracking Process

We studied the effects of the Ca and Sr additions on the microstructure and the cracking process of magnesium alloys with in-situ scanning electron microscope (SEM) images. We found that the Ca addition is not only able to refine the Mg17Al12 phase but also form a new Al2Ca phase, which lead to improved ductile of cast magnesium alloys at elevated temperature. The MgAlCaSr phase can be improved the hot resistance. However, the number of cracks per unit area increases with increasing Ca addition.

Effects of Distance and Alignment Holes on Fatigue Crack Behaviors of Cast Magnesium Alloys

2008 ◽  
Vol 33-37 ◽  
pp. 13-18 ◽  
Author(s):  
Xi Shu Wang ◽  
Jing Hong Fan ◽  
Bi Sheng Wu ◽  
Ying Li
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Magnesium Alloys ◽  
Fatigue Crack Propagation ◽  
Fatigue Cracking ◽  
Mg17al12 Phase ◽  
Small Cracks ◽  
Cast Magnesium Alloys ◽  
Cast Magnesium ◽  
Small Holes

To study the fatigue microcrack initiation and propagation behaviors of cast magnesium alloys, the small fatigue crack propagation tests were carried out using the in-situ observation with scanning electron microscope (SEM). All initiations and propagations of fatigue small cracks focused on effects of the interaction of artificial two small holes, which there are the different distances and alignments of two small holes. The results indicate that the fatigue small cracks of cast magnesium alloys occurred mainly at the defects or root of notch but the early stage crack propagations were influenced on the distance and alignment between two small holes. For cast AM50 and AM60B alloys, the fatigue small cracking prior to occurred at the weak dendrite boundary and had some concomitances such as the plastic deformation on surface of α-Mg phase. For AZ91 alloy, the fatigue cracking characterization depended mainly on the brittle properties of β-Mg17Al12 phase, which the multi cracks occurred at the boundaries of β-Mg17Al12 phase. The effect of notch on the fatigue cracking behavior becomes weaker when the radius of notch is over 3-4 times than that of average α-Mg grain size. The fatigue crack propagation behaviors varied with the different arrangements of two small holes. The effects of distance and alignment of two small holes on the fatigue crack propagation behaviors are also obvious.

Effect of Briquetting Pressure on the Performance of In Situ Formed Sialon in Al2O3-C Refractory Bricks

2014 ◽  
Vol 881-883 ◽  
pp. 1049-1052 ◽  
Author(s):  
Nai Peng ◽  
Cheng Ji Deng ◽  
Hong Xi Zhu
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
X Ray Diffraction ◽  
X Ray ◽  
Z Value ◽  
Refractory Bricks ◽  
Scanning Electron

In this paper, the effects of briquetting pressure on the performance of in-situ formed Sialon in Al2O3-C refractory bricks are investigated. The phase compositions and microstructure of the Al2O3-C refractory were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM).The results show the briquetting pressure hardly has effect on the phase of the sintered specimens, two new phases of Sialon with a Z value of 2 and SiC formed. The micrographs of Sialon crystals have the shape of both column and tabular column, but with a cone tip in the specimens sintered at 200MPa and 300MPa and smooth tip in specimens sintered at 400MPa and 500MPa.

In-situ Fracturing of Wood in the Scanning Electron Microscope

Holzforschung ◽  
1996 ◽  
Vol 50 (6) ◽  
pp. 487-490 ◽  
Author(s):  
Josef Bodner ◽  
Gerhard Grüll ◽  
Michael Georg Schlag
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Scanning Electron
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