The wide-gap aluminothermic rail welds with root opening of 50-70 mm were produced using plain carbon steel rail and non-alloy aluminothermic charge. Mechanical PROPERTIES and micro-structure of the weld metal and HAZ as well as the impact energy and the fracture toughness of the welds were investigated. The yield and tensile strength of wide-gap welds were about 98% and 95% of the base metal, respectively. Both minimum and maximum hardnesses of the joint were seen in HAZ which were related to the grain coarsening and normalizing, respectively. The mean value of wide-gap weld fracture toughness is more than narrow-gap weld. Moreover, trans-granular cleavage indicated the brittle fracture mode of the weld metal.

In spite of excellent corrosion resistance, good ductility and low cost of AISI 316 austenitic stainless steel, the low hardness and poor mechanical characteristic of material restricts its applicability in several industrial services. To improve the mechanical PROPERTIES AlFeCuCrCoNi-WC10 high-entropy alloy coatings were deposited via laser cladding on austenitic stainless steel AISI 316 substrate. The influence of WC on phase constituents, microstructure, microhardness and elemental distribution were investigated using X-ray diffractometry, optical microscopy microhardness tester and FESEM-EDS (Energy Dispersive Spectroscopy), respectively. The XRD peaks revealed that as clad AlFeCuCrCoNi-WC10 multiple principal element alloy coating composed of BCC, FCC and W-rich phase. The cladding zone microstructure is mainly consisting of fine-grained non-directional and equiaxed crystals away from the base material and columnar grains near the base material. The energy dispersive spectroscopy indicated segregation of W and Cr in the interdendritic region.  However, other elements of the multiple principal element alloy are observed to be uniformly distributed throughout the cladding. The microhardness of the AlFeCuCrCoNi-WC10 (670 Hv0.5)high entropy alloy coating was 4.5 times greater than that of substrate AISI-316.

Cladding of steel with titanium alloys to improve corrosion behavior and reduce production costs, is used widely in aerospace, chemical and nuclear industries. Roll bonding is one of the solid state processes to produce this combination. In this research the high quality bonding of hot roll bonding of titanium on steel Substrate was investigated in terms of physical and mechanical PROPERTIES, and the effect of copper interlayer to prevent interdiffusion was evaluated. The microstructure at interface was observed by an optical and scanning electron microscope and the presence of intermetallic phases in the reaction zone was examined by X-ray diffraction on the fracture surfaces of the joints. The experimental results showed that the volume fraction of intermetallic will be controlled effectively, because there is not enough time for interdiffusion of the elements. Total thickness of intermetallic layers and microhardness at the interface increased with increasing bonding temperature.

In this research, welding of Incoloy 925 nickel-iron based superalloy was examined in order to investigate the effect of chemical composition of used filler metals on the microstructure, mechanical PROPERTIES and corrosion resistance of welded zones. For this purpose, shielding gas tungsten arc welding process and two nickel-base filler metals including ERNiCrMo-3 and ERNiCr-3 were used. Morphological observations showed that at the end of solidification, microstructure of weld metals were stabilized in the form of austenitic with dendritic morphology. In addition, in tensile test although tensile strength of weld metals were lower than Incoloy 925 base alloy but rupture in specimens occurred in heat-affected zone of base metal. In charpy impact test, ERNiCr-3 weld metal was broken by more attracting fracture energy compared to Incoloy 925 base metal and ERNiCrMo-3 weld metal. By performing potentiodynamic polarization test also determined that the corrosion potential difference between base metal and ERNiCrMo-3 weld metal can persuade occurrence of galvanic corrosion in the joint. Finally, with regard to the achieved results, ERNiCr-3 filler metal was diagnosed better selection for welding of Incoloy 925 superalloy.

Thixoforging is known as a modern process for the production of parts in semi-solid state that has been developed in recent years. Thixoforging involves forging of nondendritic structure ingots in the temperature range of liquid and solid phases. The purpose of this study was to investigate the effect of primary microstructure, Hydraulic Ram speed and heat treatment on METALLURGICAL and mechanical PROPERTIES of parte in thixoforging process. Microstructural study has been investigated by using optical microscopy, scanning electron and image analysis software. Results show that the increase of forming speed from 1 to 5 mm/s cause the decrease of grain size from 85 to 73 micrometer in which case the final compressive strength equal 433 MPa were measured. Also, accomplishment of T6 heat treatment causes formation of globular Si eutectic phase and precipitation of Mg2Si hard particles in matrix phase that lead to increasing the compressive strength from 433 to 522MPa and hardness increase from 79 to 88 HV.

Explosive welding is used for excellent bonding of similar and dissimilar materials with a wide variety of thicknesses, area dimensions and different thermal and mechanical PROPERTIES. In this study, an Al/St/Al multilayer sheet was fabricated by explosive welding process and the effects of annealing temperature on the interfacial PROPERTIES of explosively bonded Al/Cu bimetal have been investigated. For this purpose, hardness changes along the thickness of the samples have been measured, and the thickness and type of intermetallic compounds formed at the joining interface have been explored by means of optical microscopy (OM), scanning electron microscopy (SEM) and also energy dispersive spectroscopy (EDS). By heat treatment of the samples at 300, 350 and 400oC, it was observed that intermetallic layer was formed at the interfaces. The obtained results indicate that, with the increase of the annealing temperature, the thickness of intermetallic compounds has increased and the amount of hardness along the thickness of the joining interface has diminished. In the annealed sample at 300°C for 60 min, it was observed that intermetallic layers have formed at the interface of Al/St bimetals. These layers consist of the intermetallic compound Al2Fe and its thickness becomes to about 35 mm at some points.

The research is based on experimental tests, lap joint welding of 5456 aluminum alloy was carried, so that the hard working H321 sheet with the thickness of 5 mm was placed on an annealed sheet with the thickness of 2. 5 mm and has been investigating the simultaneous effects of parameters such as rotation speed and welding speed on METALLURGICAL and mechanical PROPERTIES in friction stir welding process. The results showed that increasing of rotation speed and reducing of welding speed (increase of welding step) causes increased heat input, increase vertical flux, increase hook height and reduction in effective Sheet thickness and it is causing the failure from the thermomechanical zone where the maximum heat input applied also, increasing of welding speed causes reduction in the material mixing and hook height and it causes an interface failure. It was observed with an examination of the results due to the differences in thickness of the sheets, existence of hook defect and its appropriate height and orientation is useful in this joint and causes an increase in strength and failure was in the base metal of the sheet with a thickness 2. 5 mm in a tensile test.

In recent years, more attention is paid to stainless Steel 316L as fracture plate and fixation in human’s body. Present studies are focused on surface and METALLURGICAL PROPERTIES of this material. Biocompatibelity of this material and its superior mechanical PROPERTIES has made it the most demanded biomaterial. In this research, four different implants are investigated in three stages. Four commercial brands of implants from Germany, Switzerland, India and Iran are selected. Mechanical tests such as impact, hardness and fatigue are done on this implant, according to their corresponding standard. Scanning electronic microscope (SCM) is used to investigate surface fracture, and optical microscope for microstructure, to determine kind of fracture. Corrosion test is simulated in the body using hank solution to determine implant corrosion. Aim of this research is quality evaluation with respect to mechanical PROPERTIES and failure resistance. Moreover, regardless of brand it is aimed to investigate medical/METALLURGICAL methods to present implant failure inside the body. Iranian brand is more or less similar to Sweden and German brand, however, Indian brand is not compatible to medical standards in term of microstructure, chemical composition and mechanical PROPERTIES.

High strength low alloy steels are widely used in gas industry, so shield metal arc welding in pipelines to transport natural gas from Iran is of great importance. For experimental investigation of seam weld and integrity of girth weld, destructive and non-destructive tests are required. In this article the effects of normal heat treatment on PROPERTIES of multi pass welding in different situations (6-7: 30, 7: 30-9, 9-10: 30, 10: 30-12) with 36 in outside diameter is evaluated by chemical, metallography, tensile, toughness and hardness. The result shows that normalizing increases ferrite ratio in root pass and weld cap pass respectively 24 and 6 percent than base steel. Also the increase rate of ferrite in root, hot, filler, and the cap pass are respectively 32, 14, 12 and 7 percent before than normalizing. The elongation weld of was increased ratio than before the heat treatment in base metal respectively 65 and 5 percent. The impact energy alignment to weld (9-10: 30) had a rate of 70 percent increase before the heat treatment. The increase rate of C, V and Ti in the weld zone according to base metal in situation of 6-7: 30 are respectively 0. 01, 0. 003 and 0. 005.