Papers by Keyword: Hardness

Abstract: U71Mn rails were welded by ultra-narrow gap welding with constrained arc by flux strips，then normalizing treatment and stress relief annealing were performed for the joints. Another sample with no heat treatment, was studied in comparison. The effect of post weld heat treatment on the hardness and microstructure of rail joint were studied by scanning electron microscope (SEM) and microhardness test. The test results showed that normalizing treatment can improve the hardness of weld seam and base metal, and stress relief annealing couldn’t improve the hardness of joints obviously.

Abstract: The effect of In addition on melting behaviors, microstructure and properties of Zn-5Al solder were investigated. It was found that addition of In decreasing the melting point of Zn-5Al solder. XRD analysis confirmed the presence of Indium in form of α-Zn+β-In solid solution. The segregation of In on grain boundary was observed. Segregation of In on grain boundary caused a significant decrease of strength of the Zn-5Al-In solder compared to Zn-5Al.

Abstract: Studied the effect of the introduction of cobalt into the charge powder fused wire system Fe-C-Si-Mn-Cr-Ni-Mo-V, used in cladding assemblies and equipment parts and mechanisms operating under abrasive and abrasive shock loads., the samples cored wires were manufactured in the laboratory conditions using appropriate powder materials and as a carbonfluoride contained material were used the dust from gas purification of aluminum production.

Abstract: Studied the effect of the introduction of vanadium and cobalt into the charge powder fused wire system Fe-C-Si-Mn-Cr-Ni-Mo-V, used in cladding assemblies and equipment parts and mechanisms operating under abrasive and abrasive shock loads. the cored wires samples were manufactured in the laboratory conditions and using appropriate powder materials and as a carbonfluoride contained material were used the dust from gas purification of aluminum production.

Abstract: Recently, the laser welding technology of carbon steel is being widely used compared with arc welding technology for its better welding characteristics. In the present study, the influence of welding conditions of both laser beam welding (LBW) and gas metal arc welding (GMAW) as a comparative study on the weld joint microstructures, hardness distribution and fatigue properties crosses the butt-welded joints of dual phase (DP) steel and mild steel are investigated. The results show that LBW produced narrow welds with complete penetration while GMAW produces wide fusion and heat affected zones. The microstructure of the fusion zone of laser welded DP steels contains mainly bainite, martensite, and a few amount of acicular ferrite phases. Hardness values of the heat-affected zone (HAZ) for dual-phase (DP) steels showing lower values for both LBW and GMAW processes due to the tempering action of the martensite phase. A narrow softening region was clearly observed in the HAZ welded for LBW compared with GMAW. In general, the fatigue life of the welded joints is improved by using laser welding technique.

Abstract: The mechanical properties of sintered nanostructured Pb_1-xCu_xTe (0 ≤ x ≤ 0.2) alloy systems were investigated using nanoindentation technique. The powder precursors of the designed systems were prepared by ball milling technique and sintered by hot isostatic pressing. Cu acts as a dopant in these alloy systems, and an increase in its concentration, up to x = 0.1, leads to a more dense and refined nanostructure along with enhancements in both hardness and Young’s modulus. The Cu addition caused an apparent embrittlement in the materials, and spalling of the materials was recognized when x exceeded 0.15. These results imply that design parameters of complex mechanical environments under thermal shocks and vibrations cannot be determined only in terms of hardness and Young’s modulus of thermoelectric systems like Pb_1-xCu_xTe alloys.

Abstract: This paper is a contribution to the study of the microstructure in welded joint of INC 738 LC. It presents the microstructures obtained after real welding and also after thermal cycle simulation of welding by rapid heating and cooling treatments in specific simulation equipment. We were focusing on the temperature range [900°C, 1100°C] which is the temperature range of main phases occurrence, as coarse γ’primary, fine γ’ secondary and carbides. Optical microscopy and microhardness measurements were used as characterization techniques. We have found that the obtained microstructures by thermal cycle simulation of welding correspond to those observed in the same zone of the real welded joint performed by real welding.

Abstract: In present scenario, nanocomposites are playing an imperative role in most of the industrial application due to their outstanding performances with good mechanical properties. The aim of this research is to study the effect of tool rotational speed and traverse speed on micro structural and hardness properties of fabricated surface nanocomposites of Al-Al₂O₃. By varying tool rotational and traverse speed at a constant volume percentage the surface nanocomposites were produced by applying one pass of friction stir processing. A clear view of material flow and defect characterization in the stir zone were studied. Optimum condition of tool rotational speed of 1120 rpm and tool traverse speed of 16 mm/min was obtained to produce a defect free surface nanocomposite. Microstructure observations were carried out through optical microscope and micro hardness test were conducted by using Vickers micro hardness tester. From the phase volume fraction analysis, it was observed that the Al₂O₃ nanoparticles were well dispersed in the stir zone. It was found that, the tool speed and traverse speed had a significant impact on microstructure properties as well as mechanical properties of the fabricated surface nanocomposite. From the final results it was found that a mixture of dynamically restored ultra fine grins with a mean size of ~80 nm and the average micro hardness value of 130HV were achieved through a fabricated aluminium Al₂O₃ nanocomposite.

Abstract: Many Ti-alloys were designed by introducing iron (Fe) as an alloying element to improve the mechanical properties and reduce the cost of the alloys. Therefore, new (α+β) titanium alloys, Ti-6Al-(1-3)Fe were developed through complete replacement of vanadium (V) by iron with major composition modifications of Ti–6Al–4V, which is commonly used for aerospace applications. Ti-Al-Fe alloys were melted through vacuum arc melting technique followed by hot rolling. This study aims to investigate the effect of Fe addition on the microstructure and hardness of emerging (Ti-Al-Fe) alloys in comparison with Ti-6Al-4V alloy. Results reveal that the microstructures are typical lamellar structures, and the hardness ranges from 32 to 40.7 HRC. The hardness of the investigated alloys increases with increasing Fe content.

Abstract: TiB₂p/Al-10Zn-1.7Mg-1.0Cu-0.12Zr composite was prepared by synthesis of in-situ Al-TiB₂ master alloy, high purity aluminum, pure zinc, pure magnesium, Al-50 wt% Cu and Al-4 wt% Zr master alloys. The mass fraction of TiB₂ particles was varied from 0% to 9.14%. SEM and TEM were applied to evaluate the microstructure and phase component. HB hardness test were carried out on hardness value of the matrix alloy and the composite. The results showed that TiB₂ particles uniformly distributed in the composite and well combined with the matrix alloy. The average grain size of the composites decreased from 110.35μm to 52.07μm when the TiB₂ particles is 4.47%, and the grain size changed slightly when TiB₂ content increased further. The hardness value of the composites which raised from 189HB to 206HB is superior to that of the matrix alloy. As the content of TiB₂ particles increased, HB hardness value also increased.