Influence Of Aging Heat Treatment Research Articles

Influence of aging heat treatment on microstructure and mechanical properties of a novel polycrystalline Ni3Al-based intermetallic alloy

A novel polycrystalline Ni3Al-based intermetallic alloy was prepared using the vacuum induction melting process. Subsequently, the alloy was subjected to the solution-treatment underwent two different aging processes: 870 °C for 24 h in air cooling, referred to as AT 1, and 1060 °C for 4 h in air cooling followed by 870 °C for 24 h in air cooling, referred to as AT 2. The effects of different aging processes on the microstructure and mechanical properties of the polycrystalline Ni3Al-based intermetallic alloys were analyzed. Results indicated the cubicity of the primary γ′ phase within the dendritic γ+γ′ structure of the AT 2 sample was significantly enhanced, yielding the best overall mechanical properties for the alloy. The percentage elongation increased from less than 3 % for the AT 1 sample to about 4.5 %, highlighting a notable enhancement in room temperature tensile plasticity. The creep rupture time at 1100 °C/30 MPa reached 113 h. The α-Cr particles in the As-cast and solid solution alloy gradually transformed into Cr23C6 during the aging process, exhibiting the orientation relationships of (020)Cr23C6||(010)γ' and [103]Cr23C6||[103]γ'. High-temperature aging treatments resulted in Cr23C6 particles that provided enhanced precipitation strengthening effects, thereby improving the creep rupture performance of the Ni3Al-based intermetallic alloys. Following high-temperature aging, a four-layer interface structure formed around the blocky γ′ matrix phase, which altered the alloy's fracture mechanism from a brittle intergranular fracture to a ductile transgranular fracture.

Fast epitaxial brazing of DD6 single crystal superalloy using novel NiCoCrAlNbTi high entropy filler alloy

In recent years, Ni-based single crystal superalloys are widely applied in the fabrication of blades and vanes in aero-engine industry due to the excellent high temperature properties. In this study, a novel high entropy filler without Si and B was proposed. The melting point of the newly developed Ni-Co-Cr-Al-Nb-Ti filler was 1155ºC and fast epitaxial brazing DD6 single crystal superalloy was realized under the brazing condition of 1200ºC for 30 min. Furthermore, the influence of aging heat treatment on the interface microstructure and joint strength was investigated. The as-brazed joint interface mainly consisted of γ, γ’, γ’’-(Ni,Co,Cr)3Nb and NiAl phase. After aging treatment, element distribution became more uniform and the size of intermetallic phase was refined. The γ+γ’ phase in brazing seam exhibits same [001] orientation with DD6 substrate. The orientation relationship between γ and γ’’ was also analyzed. The joint tensile strength tested at 980ºC was 559 MPa.

Influence of aging heat treatment at 180 °C on cavitation erosion for aluminum alloy type 5083 in cold rolled state

Aluminum-based alloys have wide applicability in the construction of aircraft, vehicles, and ships. Some of their components, during operation, such as the radiators and the rotors of the cooling pumps in the vehicles, and the propellers of fishing and pleasure boats are affected by the abrasive, chemical and cavitational corrosive action of the water. At certain hydrodynamic flow regimes, the most dangerous becomes the corrosion through cavitation. Operation in such regimes inevitably leads to damaging the structure, due to cyclic stresses of the micro-jets and shock waves generated by the implosion of cavitation bubbles. Although the chemical constitution and alloying with other chemical elements increase the mechanical properties, the service life is still limited when operating in high-intensity cavitation flows. Therefore, researchers are looking for solutions to improve this resistance through various treatments, such as bulk heat. Research heading the same direction, but, made on 5083 alloy, is presented in this paper. The results highlight the behavior of a modified structure compared to the semi-fabricated state (obtained by rolling), through three durations regimes (one hours, 12 hours and 24 hours) of aging heat treatment to 180 °C temperature, after hardening treatment at 450 °C. The cavitation tests were performed in the Laboratory of the Polytechnic University of Timisoara, on the standard vibrating device with piezoceramic crystals. The results were expressed by curves and parameters specific to the evaluation of cavitation resistance, and by macro and microscopic images, showing the unique aspects of the connection between the structure and the mechanical properties obtained through heat treatment regimes. Thus, comparison of the results, including with the delivery state (laminated product), shows that the highest resistance is provided by the treatment at 24 hours. At the same time, the erosion, of pitting and caverns type, and differs from one structure to another.

Effect of aging heat treatment on microstructure of Ni-based single crystal superalloys

The precipitation and evolution of γ′ precipitates for various aging heat treatment regimes are studied experimentally in Ni-based single crystal superalloys for both standard heat treatment and long-term aging samples. The focus of this paper is to explore the influence of aging heat treatment on the evolution of the morphology and the distribution of γ′ precipitates. It is demonstrated that the splitting and shrinkage phenomena appear at low aging heat treatment temperatures, and the passivation phenomenon occurs at a high aging temperature of 1200°C. The uniform cubic γ′ particles can be obtained at 1100°C/4 h for the standard heat treatment samples and 1150°C/8 h for the long-term aging ones. This research is beneficial for the study of the rejuvenation aging heat treatment in re-service nickel-based superalloys.

Influence of Aging Heat Treatment on Pitting Corrosion Resistance of Martensitic Stainless Steel

In this research is to study the influence of the aging heat treatment on the pitting corrosion resistance of martensitic stainless steel (MSS), where a number of specimens from martensitic stainless steel were subjected to solution treatment at 1100 oC for one hour followed by water quenching then aging in the temperatures range (500-750) oC for different holding times (1,5,10,15&20) hr. Accelerated chemical corrosion test and immersion chemical corrosion test were performed on samples after heat treatment. The results of the research showed that the pitting corrosion resistance is significantly affected by the aging temperature. Where found that the aging samples at a temperature of 500 °C have the highest rate of corrosion which may be due to an increase in the ratio of the Delta type ferrite (δ-ferrite) and very soft precipitates from other phases of heterogeneous form in the basic martensitic phase; which leads to increased corrosion rate, whereas aging samples in the temperature range (550–650) °C have the smaller rate of corrosion values, this is due to the high volumetric ratio of remaining austenite. The aging samples at temperatures above 650 °C show an average corrosion rate. It was also found that the type of pits resulting from both the chemical corrosion tests and their shape were not related to the ferrite type and the carbides present in the microstructure

Influence of aging heat treatment on microstructure and tensile properties of laser oscillating welded TB8 titanium alloy joints

Investigations were conducted on TB8 titanium alloy to assess the influence of aging heat treatment on microstructure and phase transformations induced by laser oscillating welding, and establish a correlation between tensile properties and microstructure. Low-temperature aging joint consists of ω phase and β phase, while high-temperature aging joint is comprised of α phase and β phase. The formation of poor and rich precipitation zone in weld area was due to segregation of major alloying elements like Al, Mo and Nb. Low-temperature aging deteriorates plasticity of joints, but high-temperature aging improved ambient-/elevated-temperature tensile properties. The effect of aging temperature and aging time were discussed in depth. After aging treatment at 450° Celsius for 1 h, intermediate ω phase in gathering place transformed to α phase, but dispersed ω phase still retained. With the increase of aging temperature and aging time, size of α precipitate increased. Note that there is a significant increase (85%) in tensile strength after high-temperature aging treatment and Portevin-Le Chatelier (PLC) effect can be avoided under thermo-mechanical loading conditions. It was found that after 1 h of aging treatment at 550° Celsius followed by air cooling, the welded joints owned the best tensile properties at both ambient and elevated temperature.

Effects of aging on a spray-formed Cu-Al-Ni-Mn-Nb high temperature shape memory alloy

In the present study, we have investigated the influence of aging heat treatments on the microstructure, mechanical properties and shape memory effect on a spray-formed Cu-Al-Ni-Mn alloy with minor Nb additions. The samples were homogenized and subsequently aged at distinct temperatures in order to obtain different microstructures and structural ordering states. The effects of aging heat treatment on the initial microstructure and on mechanical properties were evaluated. Also, shape memory effect was tested in terms of recovery strain Ɛemf (%), residual strain Ɛr (%) and recovery ratio (R) in different thermomechanical conditions. The compressive fracture stress reached 1400 MPa with a fracture elongation of 19% for the sample with microstructure composed of the austenite β, martensite β’ and the intermetallic AlNb3. For the same condition, the recovery strain was 1,76% and recovery ratio was 42%. Furthermore, it is proposed one mechanism based on the hampering of the phase transformation by Nb rich precipitates. It can be considered as a new route to improve mechanical property, ductility and the shape memory effect at the same time.

Creep behavior in the new AD730TM nickel-based disk superalloy – Influence of aging heat treatment and local chemical fluctuations

Transmission electron microscopy (TEM) experiments combining conventional and weak beam observations, energy dispersive X-ray and electron energy loss spectroscopies have been used to identify and quantify, in the polycrystalline AD730TM Ni-Based superalloy, the effect of isothermal aging after solution treatment in the range 730–790 °C on the creep behavior at 700 °C – 500 MPa. The microstructure of different aged crept specimens has been first characterized as the creep behavior is directly influenced by the microstructural features (size of the γ′ precipitates and of the γ-channel). The analyzes show similar results whatever the heat treatment. Then, the investigation of the dislocation configurations indicate that the deformation occurs by the propagation of straight perfect dislocations, which shear the γ-matrix and the precipitates at 730 °C and 760 °C, whereas a combination of perfect and partial dislocations is observed after aging at 790 °C. The investigation of the local chemical composition has revealed some strong local variations in Cr content within the γ-phase and smaller ones in Ti content within the γ′-phase after aging at 790 °C. These elemental concentration quantifications have been used to evaluate the antiphase boundary and stacking fault energies. This allows to interpret the presence of partial dislocations after aging at 790 °C and thus the increase in the creep strain rate when the specimen is previously aged at 790 °C.

The microstructure of a single crystal superalloy after different aging heat treatments

To study the influence of aging heat treatments on the microstructure of single crystal superalloys with high content of refractory elements and optimal the aging heat treatment regimes, a single crystal superalloy containing 22 wt% refractory elements was investigated. Results show that for the experimental alloy, even the homogenization–solution heat treatment for 25 h cannot homogenize the alloying elements completely. During primary aging heat treatment, γ′ phase grows larger and turns to regular cubes. Higher aging temperature induces larger γ′ cubes. For specimens with primary aging heat treated at 1120 °C, γ′ morphology does not change apparently during secondary aging heat treatment. For specimens with primary aging heat treatment at 1150 °C, γ′ phase in interdendrite grows obviously comparing with that in dendrites. By analyzing the precipitating kinetics of γ′ phase, it is found that owning to the dendrite segregation and different aging heat treatment temperatures, γ′ phase at different regions grows under the control of different factors at different aging heat treatment stages. The two controlling factors that are driving forces of phase transformation and element diffusion rate induce obviously different growth rates of γ′ phase. As a result, the γ′-precipitating behaviors are variable based on different solute concentrations and aging temperatures. For advanced single crystal superalloys that are supposed to be used at relatively high temperatures, the final γ′ size after aging heat treatment is suggested to be close to the crossing point of diffusion controlling curve and driving force controlling curve corresponding to the serving temperature. And then, high-temperature properties can be improved.

Influence of aging heat treatment on microstructure and hardness of single crystal Ni3Al-base superalloy IC21

The influence of high-temperature aging heat treatment on microstructure and hardness of single crystal Ni3Al-base superalloy IC21 were investigated. The results showed that the temperature and time of aging treatment had significant effect on the shape and the average size of γ’ precipitate as well as the hardness of the alloy. The average size and volume fraction of γ’ precipitate after 1320°C/10h/Ar cooling+870°C/32h/air cooling(AC) treatment were about 270nm and 63% respectively. The experimental results showed that the two-step aging treatment following the solution treatment significantly influenced the size and volume fraction of γ’ phase, i.e., through the treatment of 1320°C/10h/Ar cooling +1060°C/2h/AC+870°C/32h/AC the moderate size (about 450nm) and volume fraction (about 70%) of cubic γ’ phase obtained and the hardness of the alloy reached the maximum value of about 370HV. However, with the increase of the aging temperature or time the size and the volume fraction of γ’ precipitate increased and the morphology of the γ’ precipitate gradually changed from cubic shape to rod shape. It has been found that after 1320°C/10h/Ar cooling +1120°C/2h/AC+870°C/32h/AC or 1320°C/10h/Ar cooling +1060°C/6h/AC+870°C/32h/AC treatment the morphology of the γ’ precipitates obviously changed from cubic shape to rod shape and the hardness of the alloy decreased significantly.

Efeito do tratamento térmico de envelhecimento na microestrutura e nas propriedades de impacto do aço inoxidável superaustenítico ASTM A 744 Gr. CN3MN

O aço inoxidável superaustenítico ASTM A 744 Gr. CN3MN é aplicado na fabricação de equipamentos que trabalham em ambientes sob corrosão severa com solicitação mecânica. Nesse trabalho, investigou-se a influência do tratamento térmico de envelhecimento na microestrutura e nas propriedades de impacto desse tipo de material. Foram realizados tratamentos térmicos de envelhecimento a 900°C por 1,5; 12; 24; 36 e 48 horas. Ensaios de impacto na temperatura ambiente e a -46°C foram realizados nas amostras tratadas termicamente. As análises microestruturais foram feitas por meio de microscopia eletrônica de varredura e difração de raios X. Concluiu-se que quanto maior a o tempo de exposição do material à temperatura de 900°C, menor é a energia absorvida no impacto. Com 1,5 horas o material apresentou redução na resistência ao impacto de 128 para 25 Joules. O tratamento térmico a 900°C por 48 horas causou a precipitação de algumas fases na matriz austenítica, sendo as mais prováveis: sigma (σ), chi (χ) e carboneto M23C6.

Effect of aging on impact properties of ASTM A890 Grade 1C super duplex stainless steel

Super duplex stainless steels in the solution annealed condition are thermodynamically metastable systems which, when exposed to heat, present a strong tendency to “seek” the most favorable thermodynamic condition. The main purpose of this study was to characterize the microstructure of a super duplex stainless steel in the as cast and solution annealed conditions, and to determine the influence of aging heat treatments on its impact strength, based on Charpy impact tests applied to V-notched test specimens. The sigma phase was found to begin precipitating at heat treatment temperatures above 760 °C and to dissolve completely only above 1040 °C, with the highest peak concentration of this phase appearing at close to 850 °C. Heat treatments conducted at temperatures of 580 °C to 740 °C led to a reduction of the energy absorbed in the Charpy impact test in response to the precipitation of a particulate phase with particle sizes ranging from 0.5 μm to 1.0 μm, with a chromium and iron-rich chemical composition.

HSLA-100 Steels: Influence of Aging Heat Treatment on Microstructure and Properties

The structural steels used in critical construction applications have traditionally been heat-treated low-alloy steels. These normalized and/or quenched and tempered steels derive strength from their carbon contents. Carbon is a very efficient and cost-effective element for increasing strength in ferrite-pearlite or tempered martensitic structures, but it is associated with poor notch toughness. Furthermore, it is well known that both the overall weldability and weldment toughness are inversely related to the carbon equivalent values, especially at high carbon contents. The stringent control needed for the welding of these traditional steels is one of the major causes of high fabrication costs. In order to reduce fabrication cost while simultaneously improving the quality of structural steels, a new family of high-strength low-alloy steels with copper additions (HSLA-100) has been developed. The alloy design philosophy of the new steels includes a reduction in the carbon content, which improves toughness and weldability.

Influence of aging heat treatment on mechanical properties of biomedical Ti-Zr based ternary alloys containing niobium.

Titanium-zirconium based alloys containing a small amount of niobium were investigated in order to evaluate their possible use as biomedical materials. Zirconium, which belongs to the IVa group, is known to have good corrosion resistance and biocompatibility similar to titanium. As the titanium-zirconium system shows a complete solid solution, a wide variation of alloy design is available and large quantities of solid-solution hardening must be possible. Niobium, having a beta-phase stabilizing effect, was chosen as a ternary element in order to control desirably the microstructure. There have been no reports which suggest its harm to a living body. The alloys containing 2% or 3% niobium showed the highest hardness value after aging heat treatment at 773 K. In contrast to this, no alteration of hardness was seen in specimens aged at 1073 K. Through conventional X-ray diffractometry and in situ X-ray analysis using a hot stage, beta-phase precipitation in the A matrix was identified. From the above results, it is concluded that alloys containing 2%-3% niobium are hopeful candidates for new kinds of biomedical alloys, when they are heat treated under suitable conditions.