Showing 26 results for Heat Treatment
H. Arabi, S. Rastegari, V. Ramezani, Z. Valefi,
Volume 10, Issue 2 (6-2013)
Abstract
The objectives of this research were to find an economical way of reducing porosities in the microstructure of coatings deposited by flame spraying technique on CK45 steel and also trying to increase their cohesive strength to the substrate, so that the overall wear properties of this type of coating can be improved. So several specimens from this steel coated with NiCrBSi powder under specific conditions were subjected to various furnace heat treatment at 1000, 1025, 1050, 1075 and 1100 °C, each for periods of 5, 10 and 15 minute before cooling them in air. Tribological properties of treated coatings were evaluated by pin on disc method. The results show the highest wear resistance and microhardness values observed in one of the sample was due to lower amount of porosity and higher amount of very fine Cr2Ni3B6 particles precipitated homogeneously throughout its microstructure during specific heat treatment.
N. Khatami , Sh. Mirdamadi,
Volume 11, Issue 1 (3-2014)
Abstract
The presence of alloying elements, sometimes in a very small amount, affects mechanical properties one of these elements is Boron. In Aluminum industries, Boron master alloy is widely used as a grain refiner In this research, the production process of Aluminum –Boron master alloy was studied at first then, it was concurrently added to 2024 Aluminum alloy. After rolling and homogenizing the resulting alloy, the optimal temperature and time of aging were determined during the precipitation hardening heat treatment by controlled quenching (T6C). Then, in order to find the effect of controlled quenching, different cycles of heat treatment including precipitation heat treatment by controlled quenching (T6C) and conventional quenching (T6) were applied on the alloy at the aging temperature of 110°C. Mechanical properties of the resulting alloy were evaluated after aging at optimum temperature of 110°C by performing mechanical tests including hardness and tensile tests. The results of hardness test showed that applying the controlled quenching instead of conventional quenching in precipitation heat treatment caused reduction in the time of reaching the maximum hardness and also increase in hardness rate due to the generated thermo-elastic stresses rather than hydrostatic stresses and increased atomic diffusion coefficient as well. Tensile test results demonstrated that, due to the presence of boride particles in the microstructure of the present alloy, the ultimate tensile strength in the specimens containing Boron additive increased by 3.40% in comparison with the specimens without such an additive and elongation (percentage of relative length increase) which approximately increased by 38.80% due to the role of Boron in the increase of alloy ductility
K. Tavighi, M. Emamy, A. R. Emami,
Volume 11, Issue 4 (12-2014)
Abstract
This study was undertaken to investigate the effects of Cu and solution heat treatment on the microstructure and hardness of cast Al-Al4Sr metal matrix composite. Different amounts of Cu (0.3, 0.5, 1, 3 and 5 wt.%) were added to the composite. Specimens were heat treated at 500 °C for 4 hours followed by water quenching. Microstructural studies were assessed by the use of optical microscope, scanning electron microscope (SEM) and x-ray diffractometry (XRD). The results showed that addition of 5 wt.% Cu reduces the length of large needle-like Al4Sr phase and refines the microstructure. In addition, the presence of Cu-intermetallics increases hardness of the composite. Cu mainly forms θ phase which segregates at the grain boundaries. Heat treatment partially dissolves Cu-intermetallics and homogenizes the distribution of θ phase in the matrix.
S. Niksirat, Sh. Raygan, S. Moradi Ghiassabadi,
Volume 12, Issue 2 (6-2015)
Abstract
In this research, two different carbonaceous materials (Graphite:G and Petrocoke:P) were separately
compared in terms of the carbothermic reduction of hematite and anatase in order to synthesize Fe-TiC nanocrystalline composite by mechanically activated sintering method. Powders were activated in a planetary high-energy
ball mill under argon atmosphere for 0, 2, 5, 10,and 20 h. Then, the activated powders were analyzed by XRD and
SEM to investigate phase constituents and microstructure of the mixtures. Results proved that Fe
2
O
3
and TiO
2
were not
reduced by carbonaceous materials even after 20h of milling. SEM investigations showed that G-mixture was more
homogenous than P-mixture after 20h of milling, meaning that graphite-anatase-hematite was mixed satisfactorily.
Thermogravimetry analysis was done on 0 and 20h milled powders. TG and DTG curves showed that mechanical
activation led to almost 300°C decrease in the reduction temperature of hematite and anatase in both mixtures. In the
next step, the powders were sintered in a tube furnace under argon atmosphere. In the G-mixture, anatase was reduced
to titanium carbide at 1100°C but, in the P-mixture, temperature of 1200°C was essential for completely reducing
anatase to titanium carbide.Results of phase identification of the sintered powders showed that anano-crystalline ironbased composite with titanium carbide, as the reinforcement was successfully synthesized after 20 h high-energy
milling of the initial powders and subsequent sintering occurred at 1200˚C for 1h
M. Alipour, M. Emami, R. Eslami Farsania, M. H. Siadati, H. Khorsand,
Volume 12, Issue 4 (12-2015)
Abstract
A modified strain-induced melt activation (SIMA) process was applied and its effect on the structural characteristics and hardness of the aluminum alloy Al–12Zn–3Mg–2.5Cu was investigated. Specimens subjected to a deformation of 40% at 300 °C were heat treated at various times (10-40 min) and temperatures (550-600 °C). Microstructural studies were carried out using optical and scanning electron microscopies (SEM). Results showed that the best microstructure was obtained at the temperature and time of 575 °C and 20 min, respectively. The hardness test results revealed superior hardness in comparison with the samples prepared without the application of the modified SIMA process.
T6 heat treatment including quenching to 25 °C and aging at 120 °C for 24 h was employed to reach to the maximum strength. After the T6 heat treatment, the average tensile strength increased from 231 MPa to 487 and 215 MPa to 462 for samples before and after strain-induced melt activation process, respectively. Ultimate strength of globular microstructure specimens after SIMA process has a lower value than as-cast specimens without SIMA process
H. Torkamani, H. Rashvand, Sh. Raygan, J. Rassizadehghani, Y. Palizdar, C. Garcia Mateo, D. San Martin,
Volume 14, Issue 3 (9-2017)
Abstract
In industry, the cost of production is an important factor and it is preferred to use conventional and low cost procedures for producing the parts. Heat treatment cycles and alloying additions are the key factors affecting the microstructure and mechanical properties of the cast steels. In this study an attempt was made to evaluate the influence of minor Mo addition on the microstructure and mechanical properties of conventionally heat treated cast micro-alloyed steels. The results of Jominy and dilatometry tests and also microstructural examinations revealed that Mo could effectively increase the hardenability of the investigated steel and change the microstructure features of the air-cooled samples. Acicular microstructure was the consequence of increasing the hardenability in Mo-added steel. Besides, it was found that Mo could greatly affect the isothermal bainitic transformation and higher fraction of martensite after cooling (from isothermal temperature) was due to the Mo addition. The results of impact test indicated that the microstructure obtained in air-cooled Mo-added steel led to better impact toughness (28J) in comparison with the base steel (23J). Moreover, Mo-added steel possessed higher hardness (291HV), yield (524MPa) and tensile (1108MPa) strengths compared to the base one.
N. Nikoogoftar, S. H. Razavi, M. Ghanbari,
Volume 14, Issue 3 (9-2017)
Abstract
In this research, the effect of annealing and aging temperature as well as the effect of quenching media on the microstructure, hardness and dry sliding wear behavior of Ti-6Al-4V alloy has been studied. Cylindrical samples with the diameter of 10 mm and the height of 20mm were solutionized at 930˚C and 1060˚C for 600 seconds and then were quenched in the cold water and in the air. The samples were aged at different temperature of 480˚C, 550˚C and 610˚C for 360 s to increase the hardness. Heat treated samples were tested using standard pin-on-disc test machine at the applied loads of 100, 150 and 200 N. Microstructural investigations using scanning electron microscope revealed that for the samples solutionized at 930˚C and quenched in the water, the microstructure is composed of primary α and high volume fraction of martensitic α΄ phase with fine precipitated of β between martensitic lathes. In the case of air cooled samples, transformed β has also been appeared in the vicinity of primary α. For the samples solutionized at 1060˚C and quenched in the water, fully martensitic micro structure with fine β precipitates was observed. For the sample solutionized at 1060˚C and air quenched, plate like α and lamellar grain boundary β were detected. The maximum hardness value relates to the sample solutionized at 1060˚C and quenched in water which is equal to 433 HV. Different wear mechanisms, including oxidative wear, scratch, and delamination occurred at the worn surfaces at different applied loads. For the samples quenched in the water, the oxidative wear mechanism governing at low applied load and oxide debris was observed as separate or compacted particles which formed in the contact between pin and steel counter face detached from the sample. At higher applied loads, delamination and scratch mechanism was also observed and metallic plate like debris was detached from the sample. Mechanically mixed layer (MML) was formed on the surface of the pin at high applied loads and for the samples with low hardness value adhesion marks were also revealed on the steel disc. The minimum weight loss in the wear test is related to the sample quenched from the 1060ºC in the cold water and aged at 550 ºC .
M. Tavakoli Harandi, M. Askari-Paykani, H. Shahverdi, M. Nili Ahmadabadi,
Volume 16, Issue 1 (3-2019)
Abstract
One-step and two-step annealing techniques were used to examine the relationship between microstructure and mechanical properties during compression tests in iron-based ribbons and nanostructured 1- and 2.5mm cylindrical rods. The X-ray diffraction, microstructural, and mechanical results showed that substituting Nb for Fe had a minor effect on glass-forming ability but increased the formability index. The novel two-step annealing process resulted in a remarkable formability index of 16.62 GPa, yield stress of 2830 MPa, ultimate strength of 3866 MPa, and 4.3% plastic strain. A ductile nanosized α-Fe framework and boron-containing nano precipitations, which caused Zener pinning effect, were responsible for these novel mechanical properties.
M. Karimi Sahnesarayi, H. Sarpoolaky, S. Rastegari,
Volume 16, Issue 2 (6-2019)
Abstract
In this study nanosized TiO2coatings on the 316L stainless steel substrate were prepared by means of dip-coating technique in which thickness of the coating layer increased byrepeating the coating cycles in two different routes: (I) dipping and drying,respectively, were repeated one, three and five times and finally the dried coated sample was heat treated (single); (II) multiple heat treatment performed after each dipping and drying cycle, respectively.The structural, morphological and optical characterizations of coatings as well as thickness of coatings were systematically studied.The photocatalytic activity of the various TiO2 coatings was investigated based on the degradation of an aqueous solution of Methyl orange.Moreover, thecorrosion protective properties of coatings were evaluated in both dark and UV illumination conditions based on the obtained polarization curves. The results indicated 1.75 times improvement in photocatalytic reaction rate constant, a two orders of magnitude decrease in corrosion current density in dark condition and about 140 mV electrode potential reduction under UV illumination with optimum coating preparation procedure, repeating the cycle from dipping to heat treatment three times, than the sample prepared with one time coating and heat treatment since this procedure provided not only high thickness and defect-free coating but also transparent one.
V. Dave, R. Kotian, P. Madhyastha, K. Boaz, P. Rao, B.p. Charitha,
Volume 16, Issue 4 (12-2019)
Abstract
The aim of the present study is to assess the hardness, corrosion, and cytotoxicity of a commercially available cobalt-chromium (Co-Cr) alloy before and after simulated heat treatments at porcelain firing temperature. Five Co-Cr samples were fabricated using lost wax casting procedure. Heat treatments were carried out at 650°C, 750°C, 850°C, and 950°C. Vickers hardness was measured for as-cast and heat treated samples. The corrosion test was carried out separately in 0.1 N NaCl, 1% citric acid and artificial saliva at room temperature using potentiodynamic polarization technique. Gingival tissue biopsy of patients was taken and cultured to measure the cell viability by MTT colorimetric assay. Lowest hardness was observed at 650°C. 0.1 N NaCl and 1% citric acid corrosion medium showed a similar trend of corrosion rate. The least corrosion rate was found in artificial saliva. Firing temperature has an impact on the physical, chemical and biological properties of Co-Cr alloy in long-term clinical use.
M. Azadi, M. Ferdosi, H. Shahin,
Volume 17, Issue 1 (3-2020)
Abstract
In this paper, the effects of solutioning and various aging heat treatment processes on the microstructure, the hardness and electrochemical properties of a duplex stainless steel (DSS) were studied. The evaluation of the microstructure and phase compositions were carried out by the optical microscopy (OM) and the X-ray diffraction (XRD), respectively. Electrochemical behaviors of specimens were evaluated by both potentiodynamic polarization and electrochemical impedance spectra (EIS) tests at temperatures of 25 and 60 ºC. The obtained results showed that the solutioning heat treatment increased corrosion rates with respect to the blank specimen. The aging process at 490 ºC for 20 hrs increased the volume percent of the carbide phase to the highest value (25.1%) which resulted in an increase of the hardness value to 170 VHN. The specimen which was aged at 540 ºC for 10 hrs with the Cr7C3 size of 22.8 µm, exhibited the higher corrosion resistance at both temperatures of 25 and 60 ºC with respect to other aged specimens. In addition, the temperature of 60 ºC promoted the anodic reactions in 3.5 wt% NaCl solution which decreased impedance modulus values significantly. Consequently, the carbide size was more effective parameter than the carbide content in predicting electrochemical behaviors of such alloys.
Masumeh Mohammadi, Hamidreza Rezaei Ashtiani,
Volume 18, Issue 2 (6-2021)
Abstract
The hot deformation behavior of the heat-treated AA6061 and AA 6063 aluminum alloys by T6-1, T6-2 artificial aging treatment, and O annealing treatment were studied by compression testing over a temperature range of 350–550
and strain rates of 0.005-0.1 s
-1. It was observed that the flow stresses of the studied aluminum alloys treated by the T6-1 and T6-2 heat treatments were significantly higher than those of the O annealing treatment. Moreover, the stress-strain curves of the heat-treated alloys by the T6-1, T6-2, and O heat treatments demonstrated significant softening during deformation at the lowest strain rate under any of the deformation conditions. For several strains, the activation energy of hot deformation was specified and obtained to vary significantly with strain for the heat-treated alloys by the T6-1 and T6-2 treatments. The stress-strain data calculated from a linear equation, with strain-dependent parameters, shows a great fit with the experimental data for the heat-treated aluminum alloys.
Hamid Reza Rezaei Ashtiani, Shahab Moghaddam,
Volume 19, Issue 1 (3-2022)
Abstract
In this study, the effects of heat treatment of aluminum alloy on the tube bending process were investigated in the rotary draw bending process. As two experimental and numerical simulation methods were used to determine the wall-thinning, ovality, and spring back for extruded, annealed, and aged AA6063 aluminum alloy tubes in different bending angles and bend radii. Numerical simulations were done by the finite element method with Abaqus software. The results indicated that in comparison with annealed and extruded parts, wall-thinning reduced whereas the amount of ovality and spring-back increased in the aged tubes. Also, in each case, the percentage of wall-thinning decreased with increasing bend radius, and the effect of bend radius was greater in the reduction of ovality from the bending angle. Investigations showed that the spring-back rate also decreased with an increasing bending angle.
Abdur Rahman, Serajul Haque,
Volume 19, Issue 3 (9-2022)
Abstract
The effect of the milling time & ageing on the hardness, density, and wear characteristics of Al 7150 alloy specimens made via powder metallurgy has been studied. The different constituents of Al 7150 alloy were processed in a planetary ball milling set up with a BPR of 10:1 for 5 hours, 10 hours, and 20 hours. At 400 °C, the milled powders were subsequently hot compacted in a punch die setup. The hot-pressed specimens were solutionized initially, then aged artificially at 115 °C for 3, 6, 12, 24, 30, 45, 60, and 96 hours. The relative density was inversely proportional to the milling time. Microhardness tests showed a maximum VHN of 255 was measured for the 24 h aged T6 specimens produced from 20 h milled powders whereas the non-aged specimens, made from unmilled 7150 alloy powders showed a VHN of 40. However the samples showed a decline in microhardness beyond 24 h of ageing. Under various conditions of sliding distance and loading conditions, the samples subjected to T6 aging showed a reduced volumetric wear rate indicating the beneficial effect of artificial aging up to 24 hours. The volumetric wear rate gradually declined for the samples aged beyond 24 hours of aging. The HRTEM studies revealed a high density of uniformly scattered (MgZn2) precipitates in the base matrix, as well as (MgZn2) phases precipitating along grain boundaries. The presence of such second phase precipitates in the matrix improved the wear characteristics of the alloy matrix. The results showed that optimization of process parameters such as milling time, ageing as well as reducing the particle size of the base powders, the hardness and wear behavior of Al 7150 alloy may be improved.
Mohammad Abankar, Hossein Arabi, Mohammad Taghi Salehi, Majid Abbasi,
Volume 20, Issue 1 (3-2023)
Abstract
The aims of this research were to evaluate the effects of different thermomechanical treatments on the microstructure and investigate some of the mechanical properties of a TWIP steel rich in Mn & Al. So, a block of a TWIP steel with nominal composition Fe-17.5Mn-1.36Al-0.8C was cast and then subjected to hot rolling followed by cold rolling and heat treatment. Cold rolling was performed before heat treatment in order to reduce the grain size and improve the tensile and fatigue properties. X-ray diffraction technique was used before and after the heat treatment to evaluate the possibility of any phase formation. No sign of martensitic transformation after cold deformation was observed. However, by increasing the amount of cold deformation, the number of mechanical twins and slip band increased resulted to an increase in hardness and strength. The best tensile and fatigue result were obtained after 47% thickness reduction and annealing at 715˚C for 10 min. Under these conditions, the mean grain size reduced from 138 to 9 μm resulted to an increase in yield strength from 395 to 510 MPa, and the fatigue life improvement from the mean life of 10200 for the cast sample to 21500 cycles for the treated sample, when these samples underwent fatigue tests at a stress range of 650 MPa and R=0. In addition, the diameter and depth of dimples in fracture surfaces decreased by reducing the grain size but the fracture mode was remained ductile and adequate plastic deformation occurred before failure.
Sandeep Ramasamy Periasamy, Vaira Vignesh Ramalingam, Ajay Vijayakumar, Harieharran Senthilkumaran, Vyomateja Sajja, Padmanaban Ramasamy, Samuel Ratna Kumar Kumar Paul Sureshkumar ,
Volume 20, Issue 2 (6-2023)
Abstract
Novelty: Most of the open literature research has focused on the microstructural evolution and mechanical properties of AA2050 alloy. Also, a significant study discusses the corrosion behavior of AA2050 alloy based on immersion and electrochemical characteristics. The influence of heat treatment on the microstructure and mechanical properties of friction stir processed AA2050 alloy is scarcely discussed in the open literature. The hot salt corrosion characteristics of friction stir processed AA2050 seldom exists in the available literature. This study concentrates on microhardness, tensile strength, and corrosion properties of friction stir processed AA2050. Also, the work focuses on the influence of artificial aging on the microhardness, and tensile strength of the friction stir processed AA2050.
Mohammad Alipour,
Volume 20, Issue 2 (6-2023)
Abstract
This study was undertaken to investigate the influence of graphene nano sheets on the structural characteristics and dry sliding wear behaviour of Al-5Cu-1Mg aluminium alloy. The optimum amount of GNPs for proper grain refining was selected as 0.5 wt.%. T6 heat treatment was applied for all specimens before wear testing. Significant improvements in wear properties were obtained with the addition of GNPs combined with T6 heat treatment. Dry sliding wear performance of the alloy was examined in normal atmospheric conditions. The experimental results showed that the T6 heat treatment considerably improved the resistance of Al-5Cu-1Mg aluminium alloy to the dry sliding wear. The results showed that dry sliding wear performance of without T6 microstructure specimens was a lower value than that of with T6 specimens.
Mohammad Porhonar, Yazdan Shajari, Seyed Hossein Razavi, Zahra-Sadat Seyedraoufi,
Volume 20, Issue 3 (9-2023)
Abstract
In this research, after pressing in a cylindrical mold, the AA 7075 alloy swarf was melted and cast in a wet sand mold. After rolling and cutting, sheets with two different thicknesses of 6 and 20 mm were obtained. The sheets after homogenization were solutionized at 485°C for 30 and 90 minutes, respectively, due to differences in thickness and thermal gradients. The solutionized samples were quenched in 3 polymer solutions containing 10, 30, and 50% Poly Alekylene Glycol. The results showed that melting, casting, rolling, and heat treatment of AA7075 alloy swarf similar properties to this alloy is achievable. Microstructural studies by optical microscopes (OM), Field Emission Scanning Electron Microscopy (FESEM), and X-ray diffraction (XRD) showed that by increasing the quenching rate after the solutionizing process, precipitation increases during aging. The tensile test results indicated that as the quench rate and internal energy increase, the diffusion driving force would increase the precipitation of alloying elements. Hence, this leads to an increase in hardness and reduction of its strain after aging.
Sajad Ghaemifar, Hamed Mirzadeh,
Volume 20, Issue 4 (12-2023)
Abstract
Phase transformations and the evolution of hardness during elevated-temperature annealing of Inconel 718 superalloy manufactured by the laser powder bed fusion (L-PBF) were investigated. The microstructural evolution, elemental analysis, phase formation, and hardening were characterized by scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, and Vickers indentation test, respectively. It was observed that the effect of annealing treatments is directly governed by the annealing parameters (i.e. time and temperature), for which the hardness measurement as a fruitful and convenient tool can reveal this effect. The increase of the hardness, which was obtained by the annealing (aging) treatments at the temperature range of 800-900 °C, indicated precipitation of the Ni3Nb γ˝ strengthening phase; while owing to the coarsening of precipitates as a results of overaging at this temperature range, the hardness decreased. For instance the length and aspect ratio of precipitates in the aged sample at 800 °C for 1 h is 67.14 nm and 0.32, respectively; while these values in the aged sample at 800 °C for 8 h is 78.34 nm and 0.44, respectively. On the other hand, the decrease of the hardness at temperatures of 950 and 1000 °C was attributed to the decrease of dislocation density in conjunction with the Ni2Nb Laves phase dissolution. Hence, it is crucial to determine the annealing parameters according to the required microstructure and properties.
Tumelo Moloi, Thywill Cephas Dzogbewu, Maina Maringa, Amos Muiruri,
Volume 21, Issue 3 (9-2024)
Abstract
The stability of microstructure at high temperatures is necessary for many applications. This paper presents investigations on the effect of changes in temperature on the microstructures of additively manufactured Ti6Al4V(ELI) alloy, as a prelude to high temperature fatigue testing of the material. In the present study, a Direct Metal Laser Sintering (DMLS) EOSINT M290 was used to additively manufacture test samples. Produced samples were stress relieved and half of these were then annealed at high temperatures. The samples were then heated from room temperature to various temperatures, held there for three hours and thereafter, cooled slowly in the air to room temperature. During tensile testing, the specimens was heated up to the intended test temperature and held there for 30 minutes, and then tensile loads applied to the specimens till fracture. Metallographic samples were then prepared for examination of their microstructures both at the fracture surfaces and away from them. The obtained results showed that changes in temperature do have effects on the microstructure and mechanical properties of Ti6Al4V(ELI) alloy. It is concluded in the paper that changes in temperature will affect the fatigue properties of the alloy.
