Sharif Digital Repository

The manufacture of ultra high strength materials has always been a target for aerospace and transportation industries. Currently, the limitation of energy resources even makes this goal more serious. Nowadays, more than 50% of total extrusion products are made from Al alloys and around 90% of them are the 6000 series alloys. Therefore, regarding to high strength, low weight, and hardening aluminum AA6000 alloys capabilities can play a major role in fulfilling this task. Over the last decade, a number of techniques collectively referred to as severe plastic deformation (SPD), have emerged as a promising approach for the production of bulk ultrafine-grained (UFG) nano-structured materials.... 

In this research, Al-20Si-5Fe-1Mg-xMn(x= 0,3,6) ribbons were produced by Melt spinning method. Microstructure and growth morphology of ribbons were studied by optical microscope (OM), scanning electron microscope (SEM) and X-ray diffraction (XRD). The results were compared with as cast samples. In OM results, two different zones were observed. Featureless zone (with planar growth morphology) and dendrites zone. Microstructure of ribbons were completely different from the as cast samples. It consisted of just Aluminium and silicon. XRD results approved that matter. In fact, high solidification rate of ribbons increased the solubility of silicon and other alloys in aluminium and consequently... 

Al-20Si-5Fe-3Cu-1Mg–xCr (X=0, X=1.5) ribbons were produced by melt-spinning technique at the rotating speed of 20 and 40 ms-1. The thickness of ribbons were 40 to 80 and 15 to 35 μm, respectively. The properties of as-melt spun and as-cast specimen were investigated by optical microscopy (OM), scanning electron microscopy (SEM), X-Ray diffractometry (XRD) and the microhardness method. It was found that at the air side of ribbons the microstructure was dendritic while at the wheel side it was featureless. The microstructure of ribbons at two rotating speed showed a homogenous distribution of Si particles embedded in an α-Al matrix. XRD investigations exhibited the absence of any intermetallic... 

Upset Resistance Welding (URW) is a solid-state joining process which can be used to join a variety of parts and profiles including railways, wheel rims and pipes used in oil and petrochemical industries. This process has three primary parameters, welding current, current passage time and mechanical pressure. Martensitic Stainless Steels (MSSs) due to high strength and wear resistance, good atmospheric corrosion resistance and relatively low price and Duplex Stainless Steels (DSSs) because of higher strength and better corrosion resistance in chlorine environments, are widely used in different industries. Dissimilar MSS/DSS joints are of great importance for piping, specially in oil and... 

Development of electronic industries, compression of electronic equipment, and removing lead from electronic circuits for environmental reasons, a significant challenge was created in the design and development of tin-based lead-free solders with physical and mechanical properties close to old tin-lead alloys. In this regard, the set of Sn-Ag-Cu alloys with eutectic composition and related compounds have been proposed as alloys to replace Sn-Pb solders. As a lead-free solder alloy, low melting point (≈217℃), high reliability of joints, and compatibility with various fluxes are among the properties of this category of alloys. In order to improve the mechanical properties of the joint...