Search results for "Microstructure"

FSW of AA2139-T8 Butt joints for aeronautical applications

2011

The effect of process parameters on mechanical and microstructural properties of AA 2139 T8 joints produced by friction stir welding (FSW) was analysed by means of statistical tools. Three different parameters were taken into account: angular speed ( ω), welding speed ( va), and plunging depth ( p); each of them was varied on three levels. Forces and temperatures achieved during the welding were monitored and analysed for all joints. An accurate microstructural analysis was performed: the occurrence of some remarkable defects, typical of FSW, such as tunnel or lack of penetration, was related to actual process parameters adopted. The extension of each FSW characteristic zone was measured a…

Effect of Microstructure on the High Temperature Oxidation and Pesting Behaviour of MoSi<sub>2</sub>

2004

Comparative assessment of surface roughness produced by hard machining with mixed ceramic tools including 2D and 3D analysis

2005

Abstract This paper provides a new comprehensive analysis of part surface finish in continuous dry turning of a hardened construction steel when using mixed alumina cutting tools. Consequently, the surface profiles (2D arragement) and surface microstereometries (3D arragement) generated during different hard part turning operations on a 40H low chromium alloy steel (equivalent to AISI 5140 or DIN 41Cr4), heat treated to the hardness of about 60 HRC, were evaluated. As a result, this paper aggregates the multi-parameters characterization of the surface roughness with the machined surface structure obtained at the three selected feed rates and constant cutting speed of 100 m/min. Results show…

Solid state bonding mechanics in extrusion and FSW: Experimental tests and numerical analyses

2007

In the paper the authors compare the different solid state bonding mechanics for both the processes of hollow profiles extrusion and Friction Stir Welding (FSW), through the results obtained from a wide experimental campaign on AA6082-T6 aluminum alloys. Microstructure evaluation, tensile tests and micro-hardness measurements realized on specimens extracted by samples of the two processes are discussed also by means of the results obtained from coupled FEM simulation of the processes. ©2007 American Institute of Physics

Microstructural Changes Determining Joint Strength in Friction Stir Welding of Aluminium Alloys

2005

In the paper the results of a wide experimental activity on friction stir welding (FSW) of aluminum alloys are reported. In particular the butt joints of two different materials, namely AA1050-O and AA6082-T6 were considered. Grains dimensions and precipitates density were investigated both in the parent materials and after the welding processes. Furthermore post-welding heat treatments effects on the joint strength were studied.

On the influence of tool path in friction stir spot welding of aluminum alloys

2008

Abstract Friction stir spot welding (FSSW) has been proposed as an effective technology to spot weld the so-called “difficult to be welded” metal alloys. In the paper, a variation of the FSSW process has been considered. A tool path is given after the sinking phase nearby the initial penetration site; in this way a larger welding spot is obtained and more material is involved in the bonding process. The process mechanics of such modified FSSW process is highlighted and the joint strength undergoing tensile tests is considered at the varying both of the assigned tool path and of a few process parameters. Macro- and micro-analyses are made in order to analyze the local material microstructure…

On microstructural phenomena occurring in friction stir welding of aluminium alloys

2006

Abstract The results of experimental activity on friction stir welding (FSW) of aluminum alloys are reported. Butt joints of two different materials, namely AA2024-T4 and AA7075-T6, were investigated from a metallurgical point of view. Grain dimensions and insoluble particle densities were investigated both in the parent materials and in the joints. Furthermore, the effect of post-welding heat treatments on the joint strength was studied.

Effect of microstructure and chemical composition on localized corrosion resistance of a AISI 304L stainless steel after nanopulsed-laser surface mel…

2015

Abstract Changes induced in the surface properties of AISI 304L stainless steel when it is treated with a nanopulsed ytterbium-doped fiber laser were investigated to determine the microscale distribution of its physico-chemical properties. A Gaussian energy distribution was created with a radius of 71 μm (1/e2) at the focal point. Local investigations were carried out using transmission electron microscopy to consider the effect of overlapping individual laser impacts. The results obtained reveal that laser surface melting leads to changes in the crystallographic structure of the steel through the formation of a δ-ferritic phase. It also results in the creation of an oxide layer that increa…

Corrosion Behaviour of Ti6Al4V and TiMo10Zr4 Alloys in the Ringer’s Solution: Effect of pH and Plastic Strain

2015

The corrosion behaviour of titanium alloys is not well understood – especially the role of the microstructure and plastic strain. In this paper, the influence of the microstructure and plastic strain on the corrosion resistance of TiMo10Zr4 and Ti6Al4V alloys was studied in the Ringer’s solution at 37 °C. Measurements were performed for different pH values and in aerated and de-aerated solutions using potentiodynamic polarization techniques. Results obtained on the two alloys were compared. It was shown that in the absence of plastic strain TiMo10Zr4 shows better corrosion resistance than Ti6Al4V (especially for pH = 8). By contrast, the current density in the passive range measured after 8…

WC-based thin films obtained by reactive radio-frequency magnetron sputtering using W target and methane gas

2015

Abstract Deposition of tungsten carbide (WC) films was investigated by radio-frequency reactive sputtering using a tungsten target and methane gas. The effect of some processing parameters (pressure, power, CH 4 -to-Ar gas flow ratio) upon the chemical and structural properties of the films has been investigated. The evolution of the chemical composition has been analyzed by photoemission, the microstructure has been studied through electron microscopy techniques and the crystallographic structure was investigated by X-ray diffraction as well as Raman spectroscopy. This study demonstrates that the formation of tungsten carbide is highly dependent on the deposition conditions: thin films are…