Effects of aging treatment processes on microstructures and mechanical properties of AZ63 casting magnesium alloy

The effects of three different aging treatment processes,namely single-stage,double-stage,and reverse double-stage aging treatment processes,on the microstructures and mechanical properties of the AZ63(Mg-6Al-3Zn-0.25Mn)casting magnesium alloy were investigated and compared.The results indicate that the microstructures of all the aged alloys under the three treatment processes are mainly composed ofα-Mg,Mg17Al12),and Al4Mn phases,indicating that the double-stage and reverse double-stage aging treatments have no obvious effect on the type of alloy phases.However,as compared with the single-stage and double-stage processes,the reverse double-stage process has a great effect on the quantity of the Mg17Al12phases.After the reverse double-stage aging treatment,which results in a stronger drive for decomposition of the supersaturated solid solution,the number of Mg17Al12phases precipitated in the grains significantly increases.In addition,as compared with the single-stage aged alloy,the tensile properties at room temperature for both the double-stage and reverse double-stage aged alloys are significantly improved.Among them,the reverse double-stage aged alloy achieves the highest tensile strength,yield strength,and elongation of 295 MPa,167 MPa,and 8.6%,respectively.

Effect of aging treatment on the precipitation transformation and age hardening of Mg-Gd-Y-Zn-Zr alloy

In this study, the precipitation transformation and age hardening of solution-treated Mg-9Gd-4Y-2Zn-0.5Zr(wt.%) alloy were investigated at different aging treatment parameters. The precipitation sequences of the alloy aged at 200℃, 250℃ and 300℃ are β’’(DO19) → β’(BCO) → β(FCC), β’’(DO19) → β’(BCO) → β_(1)(FCC) → β(FCC) and β(FCC), respectively. The streaks sequences of the alloy aged at 200℃, 250℃ and 300℃ are SF, SF → 14H-LPSO and SF → 14H-LPSO, respectively. For the alloy aged at 200℃ and 250℃, the increase in hardness with increasing aging time is contributed from the increase in precipitate volume fraction and the transformation from β’’ to β’ phase with basal → prismatic and spherical → spindle-like precipitate changes. The decrease in hardness after the peak-aging stage is attributed to the appearance of micro-sized β precipitates. Because of the smaller size of precipitates and the triangular arrangement of β’ precipitate, the hardness of the alloy aged at 200℃ is higher than that aged at 250℃. For the alloy aged at 300℃, the appearance of only micro-sized β precipitate and its coarsening with increasing aging time leads to the lowest hardness and an overall decrease in hardness with the aging time.

Scaling and clogging treatment of aging tunnel drainage pipes in karst areas using eco-friendly acid agent

In karst areas,the drainage pipes of aging tunnels are prone to be clogged by precipitated carbonates,resulting in lining cracking and tunnel leaking.As a result,not only the driving safety will be deteriorated,but also the water pressure on the lining might also be elevated significantly.For the structural stability and service lifespan of old tunnels,it is of great importance to remove these precipitated carbonates in time.Traditional treatment methods are often destructive to some extent or not efficient enough.This study aims to experimentally develop an eco-friendly acid-based chemical cleaning method to remove carbonate precipitations efficiently.The proposed chemical cleaning agent is an aqueous solution with strong acidity,consisting of sulfamic acid,water,and additives.The factors affecting the cleaning efficiency include the acid solubility,temperature and flow rate of the cleaning agent,as well as additives.Elevating the solution temperature to 50
C or a flow rate of no less than 0.2 m/s can improve cleaning efficiency.Although the salt effect cannot work,1 wt%of polymaleic acid as a surfactant could further promote the cleaning rate.The cleaning efficiency will increase with the flow rate in a power function.The relatively low flow rate that improves the cleaning rate considerably can avoid highpressure-induced mechanical damage to tunnel drainpipes.The waste could be easily treated to acceptable levels using commercial sewage treatment products and can also be recycled in agriculture.With the chemical cleaning,the water pressure at the arch springing of the lining will reduce with the increased radius of transverse drainpipes in a power function.The proposed acid-based cleaning method,which is highly efficient,non-or low-destructive to aging tunnels,sufficiently safe for humans,and friendly enough to the environment,will offer a promising alternative to remove the precipitated carbonates in tunnel drainpipes efficiently.

T6态热挤压Al-5Cu-0.8Mg-0.15Zr-0.2Sc-0.5Ag合金的低周疲劳行为

为了揭示经过T6处理的热挤压Al-5Cu-0.8Mg-0.15Zr-0.2Sc-0.5Ag合金在不同温度下的低周疲劳变形与断裂行为,对T6态热挤压合金进行了室温和200℃条件下的低周疲劳实验。结果表明:在室温和200℃下合金塑性应变幅与载荷反向周次之间服从Coffin-Manson公式,而弹性应变幅与载荷反向周次之间服从Basquin公式;合金在室温和200℃下低周疲劳变形时,在较低外加总应变幅下疲劳变形机制主要为平面滑移,而在较高外加总应变幅下疲劳变形机制主要为波状滑移;室温和200℃下合金的疲劳裂纹均萌生于疲劳试样表面并以穿晶方式扩展。

Effects of solution treatment and aging process on microstructure refining of semi-solid slurry of wrought aluminum alloy 7A09

A new method was exploited using solution treatment and aging process as a pretreatment in preparing semi-solid slurry with fine microstructure before isothermal treatment of wrought aluminum alloy 7A09.Parameters of pretreatment were optimized by orthogonal experiment design and proper precursor was prepared.The evolution of microstructure of semi-solid slurry during isothermal treatment was analyzed and the mechanism of microstructure refining was discussed.The result of orthogonal experiment design shows that the optimum parameters are 462 ℃for solution temperature,40min for solution time,132 ℃for aging temperature and 14 h for aging time.Microstructure of isothermal treatment is fine,homogenous,with globular solid grains and a solid fraction between 50%and 70%,which is qualified for later semi-solid forming process.Mechanism of microstructure evolution includes the agglomeration ofα-phase and Ostwald ripening.Precipitations prepared by solution and aging treatment prevent the grains from coarsening and promote the grain ripening to globular shape.

Influence of process parameters and aging treatment on the microstructure and mechanical properties of Al Si8Mg3 alloy fabricated by selective laser melting

Many studies have investigated the selective laser melting(SLM)of AlSi10Mg and AlSi7Mg alloys,but there are still lack of researches focused on Al-Si-Mg alloys specifically tailored for SLM.In this work,a novel high Mg-content AlSi8Mg3 alloy was specifically designed for SLM.The results showed that this new alloy exhibited excellent SLM processability with a lowest porosity of 0.07%.Massive lattice distortion led to a high Vickers hardness in samples fabricated at a high laser power due to the precipitation of Mg_(2)Si nanoparticles from theα-Al matrix induced by high-intensity intrinsic heat treatment during SLM.The maximum microhardness and compressive yield strength of the alloy reached HV(211±4)and(526±12)MPa,respectively.After aging treatment at 150℃,the maximum microhardness and compressive yield strength of the samples were further improved to HV(221±4)and(577±5)MPa,respectively.These values are higher than those of most known aluminum alloys fabricated by SLM.This paper provides a new idea for optimizing the mechanical properties of Al-Si-Mg alloys fabricated using SLM.

Mechanical properties, corrosion behaviors and microstructures of 7075 aluminium alloy with various aging treatments

The influence of two novel aging treatments, T6I6 (130 ℃, 80 min + 65 ℃, 240 h+130 ℃, 18 h) and high-temperature pre-precipitation(HTPP) aging (445 ℃, 30 min+120 ℃, 24 h) on the tensile properties, intergranular corrosion, exfoliation corrosion behaviors and microstructures of 7075 Al alloy was studied, which were compared with the T6, T73 and RRA treatments. Fine η′ precipitate with high density was obtained in the alloy with the T6 and RRA treatments. The η′ precipitate density in the HTPP aged alloy is decreased due to the formation of coarse particles during the pre-precipitation process at high temperature of 445 ℃. The 7075-T6I6 alloy possesses higher precipitate density and whole precipitate volume fraction within the grain than the 7075-T73 alloy, and its whole precipitate volume fraction is even greater than that of the 7075-T6 alloy. Compared with T6 treatment, the RRA, T73, T6I6 and HTPP aging treatments cause the discontinuous distribution of the η precipitates at the grain boundary, which decreases the intergranular corrosion and exfoliation corrosion susceptibility of the alloy. Meanwhile, the T6I6 and RRA treatments can keep the high strength of the 7075 Al alloy, but the studied HTPP aging and T73 treatments lower its strength.

Effects of Aging Treatment on Intergranular Corrosion and Stress Corrosion Cracking Behavior of AA7003

In order to study the effects of aging treatment on the intergranular corrosion(IGC) and stress corrosion cracking(SCC) of 7003 aluminum alloy(AA7003), the intergranular corrosion test, electrochemical test and slow strain rate test(SSRT), combined with optical microscopy(OM) and scanning electron microscopy(SEM) as well as transmission electron microscopy(TEM) observations have been carried out. The IGC and electrochemical test results showed that the IGC resistance of AA7003 for peak aged(PA) temper is the lowest, with double peak aged(DPA) the moderate, and retrogression and re-aging(RRA) the highest among three tempers, which is attributed to the continuous feature of precipitation on grain boundary of PA temper and the interrupted feature of precipitation on grain boundary of DPA and RRA tempers, as well as the wide precipitation free zones(PFZ) of RRA temper. In addition, the SSRT results indicated that all three tempers AA7003 are susceptible to SCC in IGC solution, and the change tendency of SCC susceptibility(ISCC) of AA7003 for three tempers follows the order: ISCC(RRA)<ISCC(DPA)<ISCC(PA).

Effect of Deformation and Aging Treatment on Electrical Conductivity of Cu-Cr Alloy

The effect of deformation and aging treatment on the electrical conductivity of Cu-Cr alloy was studied. The results show that deformation can reduce the electrical conductivity of Cu-Cr alloy, but deformation followed by optimum aging treatment can effectively improve the electrical conductivity of Cu-Cr alloy, under the condition of 0～70% deformation, and the electrical conductivity of Cu-Cr alloy by aging treatment increases and the aging time of obtaining much better electrical conductivity of Cu-Cr alloy decreases with increase in deformation quantity of Cu-Cr alloy. The best electrical conductivity of Cu-Cr alloy after deformation can be obtained by aging treatment at 500 ℃. And also the reasons for the variations of alloy’s electrical conductivity and the function of adding RE were analyzed.

A New Aging Treatment Way for Near α High Temperature Titanium Alloys

Two near α titanium alloys,Ti-5.6Al-4.8Sn-2.0Zr-1Mo-0.35Si(1#) and Ti-6.0Al-4.8Sn-2.0Zr-1Mo-0.35Si(2#),were solution-treated in the upper α+β phase fields,and the duplex mixture microstructures consisting of the less volume fraction primary α phase(αp) and the transformed β phase(βt) were obtained.The aging treatments were carried out at 700℃ for 1# alloy and 760℃ for 2# alloy under varied terms,respectively.It guaranteed α2 ordered phase to precipitate only in αp but not in βt for the two alloys.The slower precipitation and growth of the α2 ordered phase and silicide was observed in 1# alloy in comparison with 2# alloy.The mechanical properties including tensile strength and ductility,the creep and lasting properties at 600℃ were investigated.Prolonging aging time did not predominantly change the tensile strength and ductility for the two alloys.The 600℃/100 h thermal exposure caused a notable decrease of tensile ductility in 2# alloy though no distinct decrease could be observed in 1# alloy after the thermal exposure.The lasting property of 1# alloy was increased with prolonging aging time and finally was equal to or even better than that of 2# alloy.Nevertheless,no evident increase emerged in 2# alloy with prolonging aging time.Similarly,the creep property of 1# alloy monotonously increased with increasing aging time and finally was equal to or even better than that of 2# alloy.No evident increase could be observed for 2# alloy.It can be deduced that the overgrowth of α2 ordered phase and silicide is unable to enhance hot strength properties but cause an unacceptable damage to tensile ductility.The optimum equilibrium of the comprehensive properties depending on the proper control of α2 ordered phase and silicide can be achieved by properly selecting aging temperature and time.

EFFECT OF PROGRESSIVE AGING TREATMENT ON THE PROPERTIES AND MICROSTRUCTUR

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Effects of electric field treatment on microstructures of GH4199 superalloy after long-term aging

The effects of electric field intensity and treatment temperature on the microstructures of GH4199 superalloy after long-term aging were investigated. The results show that the number and size of carbides and TCP(σphase andμphase) phase in the alloy increase with increasing electric field intensity at the same heat treatment temperature and holding time. While the number and size of carbides and TCP phase are weekly influenced by treatment temperature with lower electric field intensity of 2 kV/cm. When the treat temperature is up to 1 093 K, annealing twins appear in the alloy, and the number of twins increases with increasing holding time. Since the electric field can provide the enough energy for the movement of vacancies and atom, it is considered that the nucleus of the twins formed with formation stack faults due to the mismatch of local atom in crystal caused by the vacancies, and the twins will grow with the increase of holding time. Meanwhile, such promoting effects on atom movement of the electric field increase with the increase of the electric field intensity, meantime the carbides and TCP phase grow fast with the increase of electric field intensity.

Transformation behavior and shape memory effect of Ti_(50-x)Ni_(48)Fe_2Nb_x alloys by aging treatment

The influence of aging treatment on transformation behavior and shape memory of the Ti 50_x Ni_(48) Fe_2 Nb_x(x=0,0.6,0.8,1.0,and 1.2) alloys was investigated using differential scanning calorimeter(DSC),mechanical drawing machine,and microhardness tester in this paper.It is indicated that the aging treatment has a significant effect on the phase transformation temperatures(M_s,M_f,M_p,A_s,A_f,and A_p) and microhardness of the samples.The phase transformation temperatures are found to decrease initially with the increasing aging temperature from 300 to 500 ℃ and increase with further increase of the aging temperature.The aging treatment at intermediate temperature between 400 and 500 ℃ results in an improved shape memory effect.In addition,the highest microhardness value is also obtained.

Microstructure and mechanical properties of Al-Zn-Cu-Mg-Sc-Zr alloy after retrogression and re-aging treatments

The mechanical properties and stress corrosion cracking (SCC) resistance of an Al-Zn-Cu-Mg-Sc-Zr alloy under different aging conditions were investigated. The dependence of microstructure and mechanical properties on aging parameters was evaluated by tensile test, hardness test and conductivity measurement. The results show that for the alloys with retrogression and re-aging treatment (RRA), the conductivity increases with the retrogression time and temperature, while the tensile strength decreases. The transmission electron microscopy (TEM) results show that the precipitates η(MgZn2) at grain boundary aggregate apparently with retrogression time and the precipitates inside the matrix exhibit the similar distribution to T6 temper, which comprises fine GP zones, large η′(MgZn2) and η(MgZn2) phases. According to the mechanical properties and microstructure observations, the optimal RRA regime is recommended to be 120 °C, 24 h + 180 °C, 30 min + 120 °C, 24 h. The strength level of the alloy after the optimum RRA treatment is similar to that in T6 condition and the SCC resistance is improved obviously in contrast to T6 condition.

Optimal Selection and Control for Precipitation of α_2 Phase in Near α High Temperature Ti Alloys during Aging Treatment

The characteristic of the precipitation and growth of α2 ordered phase during aging treatment in near α Ti alloys have been investigated in terms of the influences of aging temperature, aging time and aging manner. The results exhibit that aging temperatures influence the distribution of α2 phase precipitated and cause the changes in growth speed of α2 phase. For various aging temperatures, the time to finish precipitation of α2 phase is different. The facts that various distribution characteristics and growth speed of α2 ordered phase are caused by changed aging condition imply optimal selection and control for precipitation of α2 ordered phase reachable. Some discussions on adoptable aging steps are presented.

Atmospheric Pressure Plasma Treatment and Following Aging Effect of Chromium Surfaces

The results of atmospheric pressure plasma treatments using diffuse coplanar surface barrier discharge (type of surface dielectric barrier discharge) on chromium surfaces are reported. A significant increase of surface wettability was observed after short plasma exposition. A quantitative value of surface wettability, i.e. the surface free energy, changed from 29 mJ/m2 to over 80 mJ/m2. In time, a hydrophobic recovery of the plasma treated surfaces was observed. Careful study by surface free energy measurements and x-ray photoelectron spectroscopy was performed to be able explaining the effects of plasma treatment. Studied samples were treated in air, oxygen and nitrogen plasma and aged in air and vacuum. Main reasons for increased wettability and aging effect are surface cleaning and transformations in chromium oxide. Additionally, generation of surface nitrate groups was found on the chromium surface as a result of plasma treatment in humid air.

Overview of Hematopoietic Stem Cells in Systemic Cancer Treatment, Aging, Pregnancy, and Radiation Hormesis

Background: The unavoidable links between the benefits of conventional systemic treatment of cancer and the side effects such as lymphopenia. Objective: To analyze this phenomenon in view of the newly discovered trophic function of circulating hematopoietic stem cells (HSC) and their lymphocyte descendants. Method: We used population statistics and recent current research involving natural aging and preliminary aging with cancer, its cytotoxic therapy, eclampsia at pregnancy, and radiation hormesis. Results: In contrast to immune-defense interpretations of these health conditions, the trophic influence of HSC and morphogenic lymphocytes on natural tissue renewal and regeneration after sublethal injuries eliminates the majority of covered inconsistencies, which are inherent to the dominating idea of cellular immunity. Conclusion: Our examination led to the feeding influence of lymphopoiesis on tumor progression, an indirect mechanism of tumor growth control by systemic therapy via either destruction of trophic cells, or by competitive distraction from malignant tissue via reparation of sublethal injuries in normal tissues. Analyses also involved similarities of the mechanisms of systemic chemotherapy and total body/half body radiotherapy in low doses, as well as the futility of the theoretical opposition of the radiation hormesis phenomenon to the linear non-threshold model, dominant in radiobiology.

Trends of Noninvasive Radiofrequency and Minimally Invasive Treatment for the Management of Facial Aging

Various treatments for the management of facial aging have been performed among which noninvasive radio-frequency (RF;i.e., thermage) treatment and minimally invasive treatments are on the rise. The purpose of this study was to analyze trends of the treatment of facial aging in Korea and to investigate relationships between the use of noninvasive RF and minimally invasive treatments. A retrospective analysis conducted on data from 4021 patients showed that thermage treatment increased by 134.9% over 5 years. As a person ages, the rate of facial treatment with both the botulinum toxin (for the masseter and lines of the glabella, lateral canthus, and forehead) and the PDO thread lift increases. The use of the treatments, nasolabial fold filler and Silhouette Soft Thread, however, was not associated with aging. The patients receiving thermage treatment were less likely to undergo any of the other treatments including PDO thread lift, Silhouette Soft Thread, nasolabial fold filler, or any of the botulinum toxin treatments. Overall, the results showed that patients who had received noninvasive RF tended to receive less minimally invasive treatment.

Effect of optimal aging treatment on magnetic performance and mechanical properties of sintered Nd-Fe-B permanent magnets

The magnetic performance and mechanical properties including hardness, brittleness, fracture toughness and strength characteristics of the as-sintered and the optimal aged Nd-Fe-B magnets were examined in this work. A new method of Vickers hardness indentation combined with acoustic emission was used to test the brittleness of the magnets.The results show that the magnetic properties of the magnets could be improved through aging treatment, especially the intrinsic coercive force. But it is accompanied by a decrease of strength and fracture toughness. Theoretical calculation confirms that acoustic emission energy accumulated count value could be used to characterize the material brittleness. The bending fracture morphologies of the as-sintered and the optimal aged Nd Fe B magnets were investigated with the emphasis on the relationship between mechanical properties and microstructure using a field emission scanning electron microscopy(FE-SEM). The research results indicate that the intergranular fracture is the primary fracture mechanism for both as-sintered and optimal aged Nd Fe B magnets. Aging treatment changes the morphology and distribution of the Nd-rich phases, reducing the sliding resistance between Nd_2Fe_(14)B main crystal grains and lowers the grain boundary strength, which is the main reason for the strength and fracture toughness decrease of the aged Nd-Fe-B magnets.