Improving the Productivity and Energy Efficiency by a Heat Treatment Method Applied to Aluminum Forged Parts

In industrial applications, hot forging of AA6082 alloy is carried at 480°C. After the hot forging operation parts are cooled down to room temperature and heated again up to 540°C for solution heat treatment and artificially aged. Heating-cooling-heating cycles leads to energy and time loss in production, and have long-termenvironmental and economic impacts. Mass production of aluminum parts for applications in various industries (automotive, aerospace etc.) requires a process with higher productivity. The aim of this study was to provide time and energy efficiency by combining hot forging and solution treatment processes into a single operation. AA6082 billets were forged at 540°C for 7.5, 15 and 30 minutes in order to achieve simultaneous solution treatment. Billets were then water quenched and artificially aged. Mechanical properties (hardness, tensile strength) as well as microstructure of samples were investigated. Required mechanical properties were achieved on the samples forged and treated at 540°C for 15 and 30 minutes

Rapid Synthesis of Metallic Reinforced in Situ Intermetallic Composites in Ti-Al-Nb System via Resistive Sintering

Intermetallics are known as a group of materials that draws attention with their features such as ordered structure, high temperature resistance, high hardness and low density. In this paper, it is aimed to obtain intermetallic matrix composites and also to maintain some ductile Nb and Ti metallic phase by using 99.5% purity, 35-44 mu m particle size titanium, niobium and aluminium powders in one step via recently developed powder metallurgy processing technique - Electric current activated/assisted sintering system (ECAS). In this way, metallic reinforced intermetallic matrix composites were produced. Dominant phases of TiAl3 and NbAl3 which were the first compounds formed between peritectic reaction of solid titanium, niobium and molten aluminum in Ti-Al-Nb system during 10, 30 and 90 s for 2000 A current and 1.5-2.0 voltage were detected by XRD and SEM-EDS analysis. Hardness values of the test samples were measured by Vickers indentation technique and it was detected that the hardnesses of intermetallic phases as 411 HVN whereas ductile metallic phase as 120 HVN

Growth morphology and phase analysis of titanium-based coating produced by thermochemical method

In the present study, high-speed tool steel was used to coat titanium by pack cementation technique. Coatings show a growth morphology similar to that of the chemical vapor deposition method. Time and temperature of the coating affects its growth morphology. Coating obtained at low temperature (900 degrees C) yields morphology with growth of tiny particles while coating produced at high temperature (1000 degrees C) has a morphology with coarser particles. Phase structure of the layers also varies depending on the process time and temperature. Short coating duration yields TiC03N0.7 phase structure, whose composition is close to TiN whereas long coating duration combined with high temperature yields TiC0.7N0.3, whose composition is close to TiC. Mechanical properties such as hardness and resistance to abrasion also reflect changes in phase structures of different types of coating. (c) 2006 Elsevier Ltd. All rights reserved

EFFECT OF ELECTRIC CURRENT ON THE PRODUCTION OF NiTi INTERMETALLICS VIA ELECTRIC-CURRENT-ACTIVATED SINTERING

This study focuses on investigating the fabrication of in-situ intermetallic NiTi composites from a powder mixture containing the mass fractions 50 % nickel powder and 50 % titanium powder. The elemental powders were mixed in the stoichiometric ratio corresponding to the NiTi intermetallic molar proportion of 1 : 1, ball-milled and uniaxially compressed under a pressure of 170 MPa. Sintering was then carried out for 15 min in a steel mold using the electric-current-activated sintering method. Electric-current values of 1000 A, 1300 A and 2000 A were used for the sintering while keeping the voltage in the range of 0.9 V to 1.2 V. The phases in the samples were analyzed with XRD and their Vickers hardness was measured as (701 +/- 166) HV0.05. Energy dispersive X-ray spectroscopy carried out with a scanning electron microscope (SEM-EDS) showed that the microstructures of the samples consist of different phases such as Ti, Ni2Ti3, NiTi2, Ni3Ti and TiO2 as a function of electric current. The XRD analysis also supported the SEM-EDS results. The nano-indentation technique was used to determine the elastic modulus of different phases

Production and Characterization of Niobium Toughened Ti-TiAl3 Metallic-Intermetallic Composite

Ti-TiAl3 in situ composites with 10 wt.% Nb were successfully prepared from Ti, Al, and Nb metallic powders by powder metallurgy processing technique of electric current activated/assisted sintering. The current and process time used for producing metallic-intermetallic composites were 2000 A and 90 s, respectively. In terms of fracture toughness, effects of addition of ductile niobium phase to Ti-TiAl3 composites were investigated. According to SEM-EDS and XRD results, the synthesized composites mainly consisted of TiAl3 matrix and dispersive Nb reinforcing phases, as well as ductile Ti phases. Hardness and fracture toughness values of the samples were measured by Vickers hardness tester under loads of 100 g and 10 kg, respectively. Fracture toughness value of TiAl3 intermetallic composites was increased with Nb ductile phase addititon from 1.69 +/- 0.05 MPam(1/2) to 5.23 +/- 0.3 MPam(1/2)

Nucleation and coating growth in the titanising of high speed steels

The nucleation and growth of the coatings are affected by each of the two components of the substrate, these being the primary carbides and the matrix containing dissolved carbon. The formation of the coating starts with the matrix on which the nuclei form, which then proceed to cover the whole of the surface of the metal by a process of lateral growth. The temperature of the process has a considerable effect on both the nucleation process and growth of the coating, an increase in the processing temperature resulting in a reduction in the nucleation density

KEY ENGINEERING MATERIALS

In the present study, alumina ceramics containing 99% and 99.8% alumina, which has been studied and indicated reliable performance in vivo and vitro experiments for another ideas before this study, were subjected to the high speed mechanical effects or ballistic performance of alumina by the way of terminal ballistic tests with armor piercing of 7.62 mm diameter was studied in order to reveal traumatological properties of the material. High values of ballistic efficiencies were obtained for thinner test material and for higher impact velocities. Results revealed the ballistic efficiency of ceramics considerably varies with the thickness and projectile velocity, for the velocities ranged from 576 to 803 m/s and thicknesses of 4.1 and 8.3 mm

Characterization of NiAl with cobalt produced by combustion synthesis

In this study, as an alloying element the effect of cobalt addition by 2.5 wt.% and 5 wt.% on the NiAl intermetallic compound produced by pressure-assisted combustion synthesis method was investigated. As starting materials aluminum powder with 15 mu m size, carbonyl-nickel 4-7 mu m size and cobalt powders 10-44 mu m size having 99%, 99.8% and 99.9% purity, respectively were used. The formation temperature of intermetallic compound for three different powders mixture determined by DSC analysis was approximately 654 degrees C. The production of NiAl was carried out in electrical resistance furnace in open air with a uniaxial pressure of 150 MPa at 1050 degrees C for 60 min. Optical and SEM studies showed that intermetallic compounds have low porosity and phase transformation has been completed. The distribution of alloying elements was confirmed by EDS analysis. The presence of NiAl and CoAl phases was determined by XRD analysis. The relative density of pure NiAl, NiAl + 2.5 wt.% Co and NiAl + 5 wt.% Co materials was 99.65%, 99.48% and 99.30% and the microhardness of materials was about 368 HV1.0, 398 HV1.0 and 425 HV1.0, respectively. (C) 2010 Elsevier B.V. All rights reserved

A study on NiAl produced by pressure-assisted combustion synthesis

The production of intermetallic compound was carried out in an electrical resistance furnace in open air under 150 MPa uniaxial pressure at 1050 degrees C for 1 hour using aluminum powder with 15 mu m size and Carbonyl-nickel powder with 4-7 mu m size having 99% and 99.8% purity, respectively. The formation temperature of intermetallic compound was determined by Differential Scanning Calorimeter analysis, and exothermic reaction of powder mixture was determined to occur at 655 degrees C. Optical microscope, scanning electron microscopy and X-ray diffraction analysis were used to characterize produced samples. These samples consist of single phase NiAl with very low porosity. Based on the Archimedes' principle, the relative density of the samples was 99.6%. The microhardness of the samples was approximately 367 +/- 17 HV1.0. it was observed that NiAl intermetallic exhibited good oxidation resistance at high temperatures in open atmosphere. The distribution of alloying elements within intermetallic compound was determined by energy-dispersive X-ray spectroscopy. (C) 2009 Published by Elsevier Ltd