تبلور مجدد و مقاومت به خوردگی آلیاژهای آلومینیوم-روی-منیزیم-مس

Effect of of Yb, Cr and Zr additions on recrystallization and corrosion resistance of Al–Zn–Mg–Cu alloys

اثر افزودن ایتربیم، کروم و زیرکونیوم روی تبلورمجدد و مقاومت به خوردگی آلیاژهای آلومینیوم-روی-منیزیم-مس

ABSTRACT

The effect of complex additions of Yb, Cr and Zr on recrystallization and corrosion resistance of Al–Zn–Mg–Cu alloy has been investigated. By complex additions of Yb, Cr and Zr to Al–Zn–Mg–Cu alloy, 20–50nm dispersoids were formed in Al matrix and identified by X-ray diffraction analysis and energy dispersive X-ray spectroscopy as Zn, Mg, Cu, Zr-containing YbCr2A120 with cubic CeCr2Al20 crystal structure. The dispersoids remarkably inhibited the recrystallization of Al matrix, and a lot of low angle grain boundary of the Al–Zn–Mg–Cu alloy by complex additions of Zr, Cr and Yb investigated by electron back scattered diffraction was retained. Complex additions of Yb, Cr and Zr to Al–Zn–Mg–Cu alloy remarkably enhanced resistance to stress corrosion cracking (KISCC) from 9.8 to 17.0MPam1/2, exfoliation corrosion from EB+ to EA and intergranular corrosion with the improved strength, fracture toughness and ductility.

 

راهنمای عملیات حرارتی آلیاژهای غیرآهنی- آلومینیوم و آلیاژهای آن Heat Treaters Guide

Heat Treater's Guide Nonferrous Alloys Wrought Aluminum and Aluminum Alloys

راهنمای عملیات حرارتی آلیاژهای غیرآهنی- آلومینیوم و آلیاژهای آن

ABSTRACT

3003 Aluminum: Microstructures. (a) 3003-0 sheet, annealed. Longitudinal section shows recrystallized grains. Grain elongation indicates rolling direction, but not the crystallographic orientation within each grain. Polarized light. Barker's reagent. 100x. (b) 3003-0 sheet, annealed. Same as adjoining microstructure, but shown at a higher magnification. Dispersion of insoluble particles of (Fe,Mn)Als (large) and aluminum-manganese-silicon (both large and small) was not changed by annealing.

 

تنش‌های پسماند در جوش‌های لب به لب اتصالات لوله غیرمشابه

Effect of the welding heat input on residual stresses in butt-welds of dissimilar pipe joints

اثر ورودی حرارت جوشکاری بر تنش‌های پسماند در جوش‌های لب به لب اتصالات لوله غیرمشابه

ABSTRACT

This study used finite element techniques to analyse the thermo-mechanical behaviour and residual stresses in dissimilar butt-welded pipes. The residual stresses at the surface of some weld specimens were measured experimentally by using the hole-drilling method. The results of the finite element analysis were compared with experimentally measured data to evaluate the accuracy of the finite element modelling. Based on this study, a modelling procedure with reasonable accuracy was developed. The developed finite element modelling was used to study the effects of welding heat input on magnitude and distribution of welding residual stresses in butt-welded pipes made of ferritic and austenitic steels. The hoop and axial residual stresses in dissimilar pipe joints of 8 mm thick for V-groove shape were studied. It is shown that the welding heat input has a significant effect on magnitude and distribution of residual stresses in the stainless steel side of the studied joints.

 

تنش پسماند حرارتی در فرآیند جوشکاری لیزری هیبریدی-GMA welding process

Numerical and experimental study of thermally induced residual stress in the hybrid laser–GMA welding process

مطالعه عددی و تجربی تنش پسماند حرارتی در فرآیند جوشکاری لیزری هیبریدی-GMA

ABSTRACT

A model based on a double-ellipsoidal volume heat source to simulate the gas metal arc welding (GMAW) heat input and a cylindrical volume heat source to simulate the laser beam heat input was developed to predict the temperature field and thermally induced residual stress in the hybrid laser–gas metal arc (GMA) welding process. Numerical simulation shows that higher residual stress is distributed in the weld bead and surrounding heat-affected zone (HAZ). Effects of the welding speed on the isotherms and residual stress of the welded joint are also studied. It is found that an increase in welding speed can reduce the residual stress concentration in the as-weld specimen. A series of experiments has been performed to verify the developed thermo-mechanical finite element model (FEM), and a qualitative agreement of residual stress distribution and weld geometrical size is shown to exist.

 

خزش در فلزات آمورف (شیشه فلزات) Creep in amorphous metals

Creep in amorphous metals

خزش در فلزات آمورف (شیشه فلزات)

ABSTRACT

This paper reviews the work on creep behavior of amorphous metals. There have been, overthe past several years, a few reviews of the mechanical behavior of amorphous metals. Ofthese, the review of the creep properties of amorphous metals by Schuh et al. though oldestof the three, is particularly noteworthy and the reader is referred to this article publishedin 2007. The current review of creep of amorphous metals particularly focuses on thoseworks since that review and places the work prior to 2007 in a different context where newdevelopments warrant.

 

جوشکاری GTAW آلیاژ آلومینیوم تیتانیوم

Effect of Vibration during GTAW Welding on Microstructure and Mechanical Properties of Ti6Al4V

تاثیر ارتعاش در طی جوشکاری GTAW روی ریزساختار و خواص مکانیکی Ti6Al4V 

ABSTRACT

The drive to improve weld quality and process parameters demands the use of improved welding tech niques and materials [1]. Titanium and its alloys are considered to be the best engineering metals for indus trial applications because of their excellent strengthto weight ratio, high fatigue life, toughness, resistance to corrosion and good fatigue strength [2, 3].

Welding methods such as gas tungsten arc, resis tance, and diffusion welding have been developed in response to the expansion of the titanium industry. 

Titanium alloys easily absorb harmful gases because of their high chemical activity, resulting in poor mechanical properties and unstable structure [4, 5]. Gas tungsten arc welding is the preferred method for avoiding these deficiencies [6]. The weld ing of titanium alloys often increases grain size in the welded metal and heat affected zones [7]. Fusion zones typically exhibit coarse columnar grains in response to prevailing thermal conditions during welded metal solidification [6]. These columnar grains produce inferior mechanical properties in the welds [1]. Methods of weld grain refinement include inocu with heterogeneous nucleants, surface nucleation induced by gas impingement, introduction of physical disturbance through techniques such as elec tromagnetic stirring [4]. Vibratory techniques, and pulsed current welding techniques [8].

رفتار زینترینگ و مقاومت هیدروژنی دولومیت واکنشی

Sintering, consolidation, reaction and crystal growth by

the spark plasma system (SPS)

رفتار زینترینگ و مقاومت هیدروژنی دولومیت واکنشی

ABSTRACT

Sintering of raw dolomite and hydroxides derived from dolomite was carried out in the temperature range 1350–1650 °C. The hydroxide derived from dolomite was developed through pre-calcination of dolomite followed by its hydration. For hydroxide development, after precalcination one sample was air-quenched and the other powder was furnace cooled before hydration. The air quenched samples showed better densification than that of the furnace cooling process at the same temperature. Fe2O3 addition enhances sintering by liquid formation at higher temperature. The grain size of doloma with Fe2O3 addition is bigger than that without additive. Hydration resistance was related to densification and grain size of sintered dolomite.

 جهت دانلود رایگان نسخه لاتین این مقاله اینجا کلیک کنید .