خستگی خوردگی در آلیاژ آلومینیوم – منیزیم بسیار ریزدانه

A microscopic study on the corrosion fatigue of ultra-fine grained

and conventional Al–Mg alloy

مطالعه میکروسکوپی خستگی خوردگی در آلیاژ آلومینیوم – منیزیم بسیار ریزدانه و مرسوم

ABSTRACT

The corrosion behavior of a nanocrystalline (NC)/ultrafine grained (UFG) Al–Mg based alloy was investigated and compared to its conventional counterpart 5083(H111). The corrosion fatigue (CF) was studied with respect to pit initiation, pit location and crack propagation as a function of environment. Scanning electron microscopy (SEM) with EDS was used to analyze the fracture surface of the failed specimen with respect to pitting characteristics, crack propagation and corrosion product. Load vs. cycles to failure was measured and S/N curves were generated for the UFG Al–Mg based alloy and the conventional counterpart 5083 in air and seawater.

 

حساسیت به ترک انجمادی در فلزهای جوش آلیاژهای آلومینیوم

Solidification crack susceptibility of aluminum alloy weld metals 

حساسیت به ترک انجمادی در فلزهای جوش آلیاژهای آلومینیوم

ABSTRACT

The susceptibilities of the three aluminum alloys to solidification crack were studied with trans-varestraint tests and tensile tests at elevated temperature. Their metallurgical characteristics, morphologies of the fractured surface and dynamic cracking behaviors at elevated temperature were analyzed with a series of micro-analysis methods. The results show that dynamic cracking models can be classified into three types. The first model has the healing effect which is called type A. The second is the one with deformation and breaking down of metal bridge, called type B. The last one is with the separation of liquid film along grain boundary, called type C. Moreover, the strain rate has different effects on crack susceptibility of aluminum alloys with different cracking models. ZL101 and 5083 alloys belong to type A and type C cracking model respectively, in which strain rate has greater effect on eutectic healing and plastic deformation of metal bridge. 6082 alloy is type B cracking model in which the strain rate has little effect on the deformation ability of the liquid film.

 

جوشکاری اصطکاکی-تلاطمی آلیاژ آلومینیوم به فولاد زنگ‌نزن

Friction stir welding of dissimilar Al 6013-T4 To

X5CrNi18-10 stainless steel

جوشکاری اصطکاکی-تلاطمی غیرهمجنس Al 6013-T4 به فولاد زنگ‌نزن X5CrNi  

ABSTRACT

The joining of dissimilar Al 6013-T4 alloy and X5CrNi18-10 stainless steel was carried out using friction stir welding (FSR) technique. The microstructure, hardness and fatigue properties of fiction stir welded 6013 aluminium alloy to stainless steel have been investigated. Optical microscopy was used to characterise the microstructures of the weld nugget, the heat affected zone (HAZ), thermo-mechanical affected zone (TMAZ) and the base materials. The results show that FSR can be used the joining of dissimilar Al 6013 alloy and X5CrNi18-10 stainless steel. Seven different zones of the microstructure in the welding are reported as follows: (1) parent stainless steel, (2) HAZ in the stainless steel at advancing side of weld, (3) TMAZ in the stainless steel at advancing side of weld, (4) weld nugget, (5) TMAZ in the Al alloy at retreating side of weld, (6) HAZ in the Al alloy at retreating side of weld and (7) parent Al alloy. A good correlation between the hardness distribution and the welding zones are observed. Fatigue properties of Al 6013-T4/X5CrNi18-10 stainless steel joints were found to be approximately 30% lower than that of the Al 6013-T6 alloy base metal.

 

رفتار خزشی آلیاژ آلومینیوم - تیتانیوم

Creep behavior of Ti-6Al-4V from 450°C to 600°C

رفتار خزشی Ti-6Al-4V از 450  تا 600 درجه سانتیگراد

ABSTRACT

We present in this paper the creep behavior of Ti-6Al-4V from 450°C to 600°C under applied stress from 100 MPa to 500 MPa. Creep behavior is studied analyzing creep damage after tests and calculating stress exponent (n) and activation energy (Q). Operating creep deformation mechanisms characterization is possible by analyzing crept microstructure by TEM. A comparison of n and Q values with values from literature and a correlation with TEM micrographs will lead us to a discussion about operating creep deformation mechanisms.

 

محدوده دمایی برای تشکیل منطقه GP در آلیاژ آلومینیوم-منیزیم-روی

The Temperature Limit for GP Zone Formation

in an Al-Zn-Mg Alloy

محدوده دمایی برای تشکیل منطقه GP در آلیاژ آلومینیوم-منیزیم-روی  

ABSTRACT

The temperature limit for GP zone formation, Tlimit was determined for an Al-5 pct Zn-2 pct Mg alloy by examining the formation process of the intermediate phase. Studies of changes in hardness and electrical resistivity, together with electron metallography permitted a conclusion that the Tlimit for this alloy is 125 °C. The nucleation mechanism of the intermediate phase is also discussed. Two types of precipitation mode were found the partly coherent phase;i.e. heterogeneous nucleation on GP zones and homogeneous nucleation respectively. It is concluded that the dominant nucleation mode is determined by the quenching conditions.

 

طیف مادون قرمز منیزیم و آلومینیم ‎جایگزین فریت‎های لیتیوم

Far-infrared spectral studies of magnesium and aluminum

co-substituted lithium ferrites

بررسی‎های طیف مادون قرمز دور منیزیم و آلومینیم جایگزین فریت‎های لیتیوم 

ABSTRACT

Polycrystalline MgxAl2xLi0.5(1−x)Fe2.5(1−x) O4 (x = 0.0, 0.2, 0.5, 0.6 and 0.7) ferrites were prepared by standard ceramic method, and characterized by X-ray diffraction and infrared absorption spectroscopy. The spectra show two significant absorption bands in the wave number range of 400–1000 cm−1 arising from interatomic vibrations in the tetrahedral and octahedral coordination compounds. The decrease in intensity and increase in broadness of bands with concentration (x) are explained on the basis of cation distribution. The force constants and bulk modulus are found to decrease with Mg-Al content (x) which suggested weakening of interatomic bonding. An alternate method for the determination of bulk modulus, longitudinal and transverse velocities is suggested. The magnetic and electrical properties of these compounds are explained in the light of structural and optical properties.

 

توزیع یونی و مغناطیسی کردن آلومینیوم جانشین فریت های لیتیمی

Ion distribution and saturation magnetization of

aluminum substituted lithium ferrites

توزیع یونی و مغناطیسی کردن آلومینیوم جانشین فریت های لیتیمی 

ABSTRACT

Ion distribution is determined in a series of aluminum substituted lithium ferrites by carefully analyzing the powder X-ray diffraction patterns. A new finding is that Al+3's substitute the Fe+3's in tetrahedral sites as well as in octahedral sites of the spinel structure. The proper formula, then, is (Fe1-a+3Ala+3)[Li0.5 +Fe1.5-(x-a)Alx-a+3]O 4, where a is approximately 0.23x2+0.22x. The saturation magnetizations are calculated and compared with the measured values.

 

خواص ساختاری منیزیم و آلومینیوم جانشین شده در فریت لیتیم

Structural properties of magnesium and aluminium co-substituted lithium ferrite

خواص ساختاری منیزیم و آلومینیوم جانشین شده در فریت لیتیم

 

ABSTRACT

The structural properties of Mg2 + and Al3 + co-substituted Li0.5Fe2.5O4 are studied by synthesizing the spinel solid solution series MgxAl2xLi0.5(1
x)Fe2.5(1
x)O4. Polycrystalline samples of this series with x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5 have been prepared by double-sintering ceramic method. The structural details like: lattice constant and distribution of cations in the tetrahedral and octahedral interstitial voids have been deduced through X-ray diffraction (XRD) data analysis. The x dependence of bond length, oxygen positional parameter, site ionic radii, bulk density, porosity and shrinkages have also been determined.