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IN modern aircraft a large percentage of the parts and details which make up the complete structure require heat treatment at some stage of fabrication. The heat‐treatment requirements necessitated by any particular design, and hence the furnace equipment of the factory requisite for dealing with the manufacture of a given machine on a production basis, is, generally speaking, a function of:—

In this study, super duplex stainless steel (SDSS) was heat-treated. The purpose of this study is to assess the effect of the cooling rate after heat treatment on the pitting corrosion of SDSS.

The heat treatment from 1,000°C to 1,300°C was applied to SDSS to check the effect of the cooling rate.

The heat treatment temperature produced a different SDSS microstructure, and the cooling rate led to the growth of austenite. The casted SDSS indicated the presence of heterogeneous austenite, and the precipitation secondary phase under 1.6 per cent precipitated to bare metal. By applying heat treatment and cooling SDSS, its corrosion resistance changes because of the change in the chemical composition. The cooling rate at 5,600 J/s has the highest critical pitting temperature (CPT) at 1,100°C, and the cooling rate at 1.6 J/s has the highest CPT at 1,200°C. Low cooling rate (0.4 J/s) made the secondary phase at all temperature range.

The effect of secondary phase not consider because that is well known to decreasing corrosion resistance.

Solution annealing is taken into account to optimize the corrosion resistance. But that is not consider the cooling rate at each temperature. This study assessed the effect of the cooling rate at each temperature point.

Manufacturers need to know the effect of the cooling rate to optimize the corrosion resistance, and this study can be applied in the industrial scene.

SDSS is hard the optimization because SDSS is a dual-phase stainless steel. Corrosion resistance can be optimized by controlling heat treatment temperature and the cooling rate. Anyone not studied the effect of the cooling rate at each temperature. The effect of the cooling rate should be considered to optimize the corrosion resistance.

For a thermal protection system (TPS) of long endurance hypersonic flight vehicle (HFV), its thermal insulation property not only determines by the manufactured morphology but also changes along time. A thermal conductivity prediction model for aerogel considering heat treatment effect is carried out and applied to solve the heat conduction problem of a TPS. The aim of this study is to provide theoretical and numerical references for further development of aerogels applying to TPSs.

A thermal conductivity prediction model for aerogel is established considering treatment effect. The heat conduction problem of a TPS is derived and solved by combining the differential quadrature method and the Runge–Kutta method. The prediction results of aerogel thermal conductivities are verified by comparing with those in literature, while the calculated temperature field of TPS is verified by comparing with that by ABAQUS.

Numerical results show that when applying the current prediction model, the calculated high temperature area in the aerogel layer is narrowed due to the decrease of the thermal conductivity during heat treatment process.

This study will be beneficial to carry out the precise design of TPS for long endurance HFVs.

This paper aims to systematically investigate the effect of the heat treatment process parameters on the microstructure and mechanical properties of the selective laser melting (SLM) AlSi10Mg alloy.

The samples with very low porosity were fabricated with optimized processing parameters on a self-developed SLM system. The heat treatment of using the temperature of 170°C∼400°C and the holding time of 0.5∼12 h was studied, and the evolution of the microstructure and mechanical properties of AlSi10Mg alloy under direct aging and annealing was investigated and obtained.

After annealing above 300°C for 1 h, the dendrite Si in the sample occurs spheroidization, and the molten pool contour becomes blurred or even disappeared completely, but low-temperature heat treatment does not change the morphology and size of grains significantly. Except for holding at 200°C for 1 h, all other heat treatment processes cause the tensile and yield strengths of SLM AlSi10Mg alloys to decrease and the elongation to increase. When the annealing temperature is higher than 200°C, the higher the temperature and the longer the holding time, the more obvious this effect is.

The correlation between the mechanical properties and microstructure of SLM AlSi10Mg alloy under different conditions was obtained. According to the characteristics of SLM forming, the direct aging and annealing process are mainly studied, which provided new information for the heat treatment of SLM AlSi10Mg alloy and promoted the engineering application of SLM AlSi10Mg alloy.

This paper aims to propose a number of approaches to reduce the temperature gradient of titanium billets in the heat treatment process.

Modeling physical processes in the induction unit is calculated by the finite element method. Required power was calculated based on the fact that all the induced power is allocated in a certain layer and there are loss flows and heating flows. Also, an opportunity is offered to reduce temperature difference using numerical optimization, control system based on proportional-integral regulator and ballast blank.

The asymmetry of the magnetic field at the ends of the inductor significantly affects the temperature uniformity along the length of the workpiece. Increasing the length of the workpiece by adding ballast blanks reduces the temperature drop. Also, increasing the non-magnetic gap in some cases it is possible to improve the quality of through heating.

The results of this study are verified only for a number of titanium alloys. Therefore, this knowledge is appropriate to apply for this type of materials. In future studies, it is possible to expand the possibilities of the considered approaches for other types of materials.

Part of the study will be used to industrial plant for purpose of heat treatment of titanium alloys workpiece. Especially, control system will be basically made based on the model.

A novel methodology of induction heating of titanium alloy Ti6Al4V in the form of cylindrical billets is presented that simplifies the process and improves temperature uniformity along the radius and length of the billet by optimizing the shape of the inductor and selecting suitable power modes.

To find out the optimum heat treatments to recover the microstructural changes of stainless steel alloys.

A total of four alloys were used in this study: two duplex stainless steel (DSS) alloys type 2304 and 2205, super DSS (SDSS) type 2507 and austenitic stainless steel alloy type 316 L. The alloys were heated to different temperatures, 750, 850, 950 and 1,050°C, for three different times, 10 min, 1 and 4 h.

The microstructural investigations showed that 2205 and 2507 behaved similarly in recovering their microstructures, especially in terms of the ferrite:austenite ratio within specific heat treatments and changing the hardness values. The results indicated that the microstructure of both alloys started to change above 750°C, the largest changes were shown at 850 and 950°C as the lowest ferrite content (FC%) was recorded at 850°C for both alloys. However, the microstructures of both alloys started to recover at 1,050°C. The reduction in the hardness values was attributed to the formation of new ferrite grains, free of residual stresses. On the other hand, the microstructure of the alloy type 2304 was stable and did not show large changes due to the applied heat treatments, similarly for austenitic alloy except showing chromium (Cr) carbide precipitation.

Finding the exact heat treatments, temperature and time to recover the microstructural changes of DSS alloys.

The paper presents a wide range of post processing heat treatment cycles performed to Electron Beam Melted (EBM) Ti6Al4V alloy and establishes correlations of heat treat process to microstructure and mechanical property (microhardness). The research also identifies the optimal heat treatment to obtain the best microstructure and mechanical properties (hardness and tensile).

Rectangular bars fabricated using EBM was used to study the different heat treatment cycles. A variety of heat treatments from sub ß-transus, super ß-transus, near ß-transus and solution aircool plus ageing were designed. After the heat treatment process, the samples were analysed for, α lath width, prior ß grain size, microhardness and nanohardness. Tensile tests were done for the heat treated samples showing most refined α lath structure with uniform globular grains.

A clear correlation was observed between α lath width and the microhardness values. The solution aircooled plus aged samples exhibited the best refinement in α-ß morphology with uniform equiaxed grains. The tensile properties of the solution aircooled plus aged samples were comparable to that of the EBM printed samples and better than ASTMF1472 specifications.

There is hardly any prior work related to post processing heat treatment of EBM built Ti6Al4V other than HIP treatments. The variety of heat treatment cycles and its influence in microstructure and properties, studied in this research, gives a clear understanding on how to tailor final microstructures and select the optimal heat treatment process.

The purpose of this paper is to study the crack‐healing mechanism of ZrO₂/SiC composite ceramics which have a high crack‐healing ability at low temperature.

The effects of dispersed SiC and the environment on crack‐healing behaviour were investigated. The fatigue strength of crack‐healed specimens was also investigated.

The main conclusions are that for crack‐healing of ZrO₂ ceramics, it is necessary to have both a SiC composite and an oxidative environment; and when ZrO₂/SiC composite ceramics are heat‐treated in air, a phase transformation attributable to the SiC composite results in crack‐healing and improvement of fracture toughness and bending strength.

An appropriate heat treatment for ZrO₂/SiC composite caused not only crack‐healing but also the improvement of fracture toughness, and created a multiplier effect on crack‐healing, bending strength and fracture toughness.

In this study, the Incoloy 825 alloy was hot-forged 90% by open die forging, and the Rockwell hardness was measured by change of solution treatment temperature and aging time. The Rockwell hardness was analyzed by the Weibull statistics.

The hot forging process generally involved heating to 1,423 K, to make grain size smaller than required grain size of 50 µm of the Incoloy 825 alloy. Thereafter, after a certain time, a forging ratio of 90% was obtained with a 5,000 ton press. At this time, the finish forging temperature was 1,173 K. To investigate the effect of solution treatment temperature, the material was maintained at 973, 1,073, 1,173 and 1,273 K for 1 h and then water-cooled. To investigate the effect of aging time, the material was water-cooled after holding for 1, 5, 10 and 30 h at 973 K.

The amount of precipitate increased with aging time, and the size of precipitate became larger. The lower the solution treatment temperature, the longer the aging time, and the Rockwell hardness increased. Shape parameter of solution-treated material increased with increasing temperature, but decreased sharply at 1,273 K. The scale parameter decreased. Shape parameters and the scale parameters of the aging treatment material increased, according to increasing of aging time.

The effect of heat treatment on microstructure and Rockwell hardness, in Incoloy 825 alloy with hot forging of 90% grain size increased and precipitates decreased with increasing solution treatment temperature, precipitate increased and precipitates' size increased with increasing aging time at 973 K. Shape parameter increased but scale parameter decreased. Shape parameters and scale parameters of the aging-treated material increased.

The deposition of particles onto a substrate during the cold spraying (CS) process relies on severe plastic deformation, so there are various micro-defects induced by insufficient deformation and severe crushing. To solve the problems, many post-treat techniques have been used to improving the quality by eliminating the micro-defects. This paper aims to help scholars and engineers in this field a better and systematic understand of CS technology by summarizing the post-treatment technologies that have been investigated recently years.

This review summarizes the types of micro-defects and introduces the effect of micro-defects on the properties of CS coating/additive manufactured, illustrates the post-treatment technologies and its effect on the microstructure and performances, and finally outlooks the future development trends of post-treatments for CS.

There are significant discoveries in post-treatment technology to change the performance of cold spray deposits. There are also many limitations for post-treatment methods, including improved performance and limitations of use. Thus, there is still a strong requirement for further improvement. Hybrid post-treatment may be a more ideal method, as it can eliminate more defects than a single method. The proposed ultrasonic impact treatment could be an alternative method, as it can densify and flatten the CS deposits.

It is the first time to reveal the influence factors on the performances of CS deposits from the perspective of microdefects, and proposed corresponding well targeted post-treatment methods, which is more instructive for improving the performances of CS deposits.