Influence of tool rotational speed on microstructure and joint strength of friction stir spot welded pure copper

Abstract: Copper is very difficult to be spot welded by conventional fusion welding techniques due to higher thermal diffusivity. Friction stir spot welding (FSSW) is a novel solid state welding process which is suitable and competent to spot weld copper. Commercially pure copper sheets of 3 mm thickness were spot welded by FSSW using industrial friction stir welding machine. The spot welds were made by varying the tool rotational speed at three levels. The spot welds were characterized using optical microscopy. The shear fracture load was evaluated using a computerized tensile testing machine. The results revealed that the tool rotational speed remarkably influenced the microstructure, shear fracture load and mode of fracture

Microstructural characterization and sliding wear behavior of Cu/TiC copper matrix composites developed using friction stir processing

Abstract: The relatively new severe plastic deformation method, friction stir processing (FSP) is a cutting-edge process to synthesize surface and bulk metal matrix composites. The present work is focused to produce Cu/TiC copper matrix composites (CMCs) and investigate the microstructure and sliding wear behavior at room temperature without lubrication. In the beginning of the process, TiC particulates were pressed in a machined groove on the surface of copper plates. The dimensions of the groove were altered to produce four different volume fractions of TiC particulates (0, 6, 12, and 18 vol.%). FSP was accomplished by an optimized set of process parameters. The microstructure was observed using optical microscopy, scanning electron microscopy (SEM) and electron back scattered diffraction (EBSD). The microstructures showed a consistent dispersion of TiC particulates in the copper matrix irrespective of the volume fraction. The dispersion was observed to be uniform across the whole stir zone region. The interfacial bonding with the copper was proper. The reinforcement of TiC particulates enhanced the microhardness and led to a reduction the wear rate of the composite remarkably. TiC particulates changed the wear mechanism and the..

Microstructure and mechanical characterization of aluminum seamless tubes produced by friction stir back extrusion

Abstract: Friction stir back extrusion (FSBE) is emerging as a novel method to produce high strength fine grained metallic tubes. The objective of the present work is to produce aluminum seamless tubes from solid cylindrical bars using FSBE and to report the microstructure and mechanical characterization. A die, tool and fixture were designed to carry out FSBE. A conventional friction stir welding machine was utilized for FSBE. A cylindrical bar of aluminum alloy AA6061-T6 was kept inside the hole in the die and extruded by plunging the rotating tool. The microstructure of the produced tubes was studied using optical microscopy. The microstructure was found to be homogeneous along the tube. The microhardness and compressive strength of the tube are presented in this paper. The results indicate that FSBE process is capable of producing sound aluminum seamless tubes

Production and characterization of titanium carbide particulate reinforced AA6061 aluminum alloy composites using stir casting

Abstract: Stir casting is an economical method to produce aluminum matrix composites. In the present work, composites of aluminum alloy AA6061 reinforced with various amounts (0, 5, 10 and 15wt. %) of TiC particles were prepared by stir casting technique. X-ray diffraction patterns of the prepared composites clearly revealed the incorporation of TiC particles without the presence of any other compounds. The microstructures of the composites were studied using optical and scanning electron microscopy. It was observed that the TiC particles distributed all over the composite and properly bonded to the matrix alloy. Local clusters of TiC particle were also seen in a few places. The result shows that the reinforcement of TiC particles enhances the microhardness, ultimate tensile strength and wear resistance of the composite. The details of fracture morphology, worn surface and wear debris are also presented in this paper

Predicting the influence of process parameters on tensile strength of AA6061/TiC aluminum matrix composites produced using stir casting

Abstract: Stir casting is an economical method to produce aluminum matrix composites (AMCs). In this work, stir casting was used to produce AA6061/15wt. % TiC AMCs. An empirical relationship was developed to predict the effect of stir casting parameters on the ultimate tensile strength (UTS) of AA6061/TiC AMCs. A central composite rotatable design consisting of four factors and five levels was used to minimize the number of experiments i.e. castings. The factors considered were stirrer speed, stirring time, blade angle and casting temperature. The effect of those factors on the UTS of AA6061/TiC AMCs was derived using the developed empirical relationship and elucidated using microstructural characterization. Each factor significantly influenced the UTS. A higher or lower values of those factors resulted in poor tensile strength. The variation in the UTS was attributed to porosity content, cluster formation, segregation of TiC particles at the grain boundaries and 2 homogenous distribution in the aluminum matrix. The UTS was high when the porosity content was low and the distribution was homogenous. The present work concludes that a careful selection and control of stir casting parameters are necessary to reduce porosity content and obtain uniform distribution to improve the load bearing capacity of the AA6061/TiC AMCs

Influence of fly ash particles on dry sliding wear behavior of AA6061 aluminum alloy

Abstract: In the present study AA6061 aluminium alloy composites containing 0, 4, 8 and 12 Wt. % of fly ash particles have been fabricated by the compocasting process. The dry sliding wear behaviour of unreinforced alloy and composites are studied using Pin-On-Disc machine. The dry sliding wear test was conducted at a load of 4.9, 9.8, 14.7, 19.6, and 24.5 N, sliding velocity of 1.57 m/s, sliding distance of 4000 m and a track radius of 100mm at an ambient temperature respectively for all the tests. Results indicate that the dry sliding wear resistance of Al-fly ash composite increases with an increase in the amount of fly ash content. The load bearing capacity of the AA6061 alloy during dry sliding wear has increased in presence of fly ash particles. Composites exhibit better wear resistance compared to unreinforced alloy up to a load of 24.5 N. Study of the wear surfaces and debris of both alloy and composites using the scanning electron microscope suggests that at high loads (>4.9 N), where fly ash particles act as load bearing constituents, the wear resistance of AA6061 Al alloy reinforced with a size range (2-3 μm) fly ash particles

Microstructure and wear characterization of aluminum matrix composites reinforced with industrial waste fly ash particulates synthesized by friction stir processing

Abstract: Fly ash (FA) is a waste product of coal combustion in thermal power plants which is available in massive quantities all over the world causing land pollution. This paper reports the characterization of AA6061 aluminum matrix composites (AMCs) reinforced with FA particles synthesized using friction stir processing (FSP). The volume fraction of FA particles was varied from 0 to 18 in steps of 6. The prepared AMCs were characterized using optical microscopy (OM), scanning electron microscopy (SEM) and electron backscattered diagram (EBSD). The wear rate was estimated using a pin-on-disc wear apparatus. FA particles were observed to be distributed homogeneously in the AMC irrespective of the location within the stir zone. The EBSD micrographs revealed remarkable grain refinement in the AMC. The 2 incorporation of FA particles enhanced the microhardness and wear resistance of the AMC. The strengthening mechanisms of the AMC were discussed and correlated to the observed microstructures. The wear mechanisms were identified by characterizing the wear debris and worn surfaces

Microstructure and mechanical characterization of in situ synthesized AA6061/(TiB2+Al2O3) hybrid aluminum matrix composites

Abstract: TiB2 and Al2O3 particulates reinforced AA6061 aluminum matrix composites (AMCs) were synthesized by in-situ reaction of titanium (Ti) and boric acid (H3BO3) powders with molten aluminum. AMCs were fabricated using an electric stir casting furnace under a controlled environment. Heat flow curves of differential thermal analysis (DTA) showed that the synthesis temperature for the formation of TiB2 and Al2O3 using Al-Ti-H3BO3 reaction system was 950°C. The in-situ synthesized composites were characterized using XRD, FESEM, TEM and EBSD. XRD results revealed the formation of TiB2 and Al2O3 particulates in the composite. FESEM micrographs revealed a homogenous distribution of both the particulates with good interfacial bonding. EBSD maps showed that the in-situ formed TiB2 and Al2O3 particulates refined the grains of the aluminum matrix from 103 μm at 0 wt.% to 14 μm at 15 wt.%. Al2O3 particles exhibited spherical shape while TiB2 particles displayed hexagonal and cubic shapes. The formation of ultrafine and nano scale thermodynamically stable TiB2 and Al2O3 particles enhanced the microhardness and the tensile strength of the 2 AMCs. The microhardness and the tensile strength were respectively 122 HV and 287 MPa at 15 wt.%

Microstructure and mechanical characterization of aa6061/tic in situ aluminium matrix composites synthesized by in situ reaction of silicon carbide and potassium fluotitanate

Abstract: In situ method of synthesizing aluminum matrix composites (AMCs) has been widely recognized and followed by researchers due to numerous merits over conventional stir casting. Aluminum alloy AA6061 reinforced with various amounts (0, 2.5 and 5 wt. %) of TiC particles were synthesized by the in situ reaction of inorganic salt K2TiF6 and ceramic particle SiC with molten aluminum. The casting was carried out at an elevated temperature and held for a longer duration to decompose SiC to release carbon atoms. X-ray diffraction patterns of the prepared AMCs clearly revealed the formation of TiC particles without the occurrence of any other intermetallic compounds. The microstructure of the prepared AA6061/TiC AMCs was studied using field emission scanning electron microscope

Microstructure evolution and mechanical characterization of friction stir welded titanium alloy Ti–6Al–4V using lanthanated tungsten tool

Abstract: Friction stir welding (FSW) exhibits significant advantages to join titanium and its alloys compared to other welding methods. FSW of 3 mm thick titanium alloy Ti–6Al–4V sheets was carried out using a lanthanated tungsten alloy tool. The traverse speed was varied from 40 mm/min to 200 mm/min in steps of 80 mm/min by keeping other parameters constant. The microstructure evolution was observed using conventional and advanced characterization techniques. The micrographs revealed a fully developed lamellar structure at 40 mm/min and a recrystallized structure in rest of the joints. An increase in β phase was observed at HAZ while TMAZ showed a distorted structure. The average grain size was observed to reduce with an increase in traverse speed. No tool wear debris was observed in the stir zone while a worm hole defect was noticed at 200 mm/min. Ti–6Al–4V hardened..