固溶-时效处理对7B04合金组织和性能的影响

通过拉伸力学性能、微观组织观察、X射线衍射物相分析及晶格常数精确测量等方法,研究固溶-单级时效处理条件对7B04合金组织和性能的影响。实验结果表明:采用合适的固溶-时效温度和时间,能使合金的力学性能得到明显的改善,经过470℃×60 min+120℃×24 h处理后,合金的拉伸性能分别达到σb=568 MPa,σ0.2=542 MPa,δ=12%;通过XRD衍射物相分析及α(Al)基体晶格常数的精确测量,能更好地表征溶质相的回溶以及时效后第二相的析出程度,指导合金固溶-时效热处理制度的选择。

时效处理对TiB_(2P)/A356复合材料组织与性能的影响

以混合盐法制备的原位自生TiB2P/A356复合材料为研究对象,采用光学显微镜、扫描电镜及力学性能测试分析等,研究时效处理对TiB2P/A356复合材料显微组织与力学性能的影响。结果表明:复合材料的最佳热处理工艺为530℃×6 h固溶处理+130℃×10 h时效处理。此时,复合材料的硬度可达76.67 HRB,与铸态相比提高73.51%;抗拉强度可达335.49 MPa,与铸态相比提高40.42%。

过时效热处理对LC9铝合金组织与性能的影响

对LC9铝合金进行了固溶-过时效热处理,采用金相显微镜、透射电镜和扫描电镜等技术手段对其显微组织进行了观察,通过电导率测试和静载拉伸试验对其性能进行了表征。结果表明:LC9铝合金(T6态)在经过固溶+双级过时效处理后,电导率由18.56 MS/m提高到了23.37 MS/m,有效改善了其抗应力腐蚀性能,同时LC9铝合金在过时效状态虽然牺牲了一部分强度,但塑韧性有了显著提升,使材料的力学性能达到了良好配合。

内燃机排气阀用镍基高温合金热处理工艺研究

排气阀作为内燃机的重要部件,其性能可靠性将直接影响设备的使用寿命.选用一种新型排气阀用镍基高温合金作为研究对象,研究不同时效热处理制度(T1:850℃×4h,AC.+730℃×4h,AC.,T2:704℃×24h,AC.,T3:760℃×16 h,AC.)对该合金室温力学性能的影响,利用金相显微镜、场发射扫描电镜研究组织变化、时效析出相γ'([Ni3(Al,Ti)])和碳化物的分布形态.γ'相呈球状分布,T1制度下的平均尺寸为50.18 nm,分别为T2制度下的3倍和T3制度下的2倍,合金室温硬度随γ'相尺寸的增加而增加,T1制度下硬度最高为347HV10,T1、T3制度下室温抗拉强度≥1200 MPa,T2制度下延伸率最佳(>30%),适用于塑性要求高的工况,T1、T2、T3室温断口均表现为微孔聚集型韧性断裂特征,裂纹沿晶界方向扩展,断面韧窝均匀分布.

Ti-15V-3Cr-3Sn-3Al钛合金固溶-时效过程的析出行为

对Ti-15V-3Cr-3Sn-3Al钛合金进行不同工艺的固溶-时效处理。采用扫描电镜(SEM)、透射电镜(TEM)等方法研究了不同固溶-时效工艺对材料的析出行为和力学性能的影响。结果表明:经过980℃/0.5h固溶处理后,组织中出现了大量亚稳态的马氏体α’相,通过随后的时效处理,将析出不同数量和形态的α相。随着时效温度升高或时间增长,析出相数量增多,形态由无规则聚集态向针状转变,析出物的尺寸和间距也增大。时效过程中材料析出大量纳米级弥散分布的α相,形成的α/β相界面对位错运动起到阻碍作用,从而提高合金强度。析出相数量越多,越细小,强化作用越大。而塑性主要取决于析出相在晶界上的分布形态和数量,晶界的连续α相分布会严重损害材料的塑性。

Effects of on-line solution and off-line heat treatment on microstructure and hardness of die-cast AZ91D alloy

The effects of on-line solution, off-line solution and aging heat treatment on the microstructure and hardness of the die-cast AZ91D alloys were investigated. Brinell hardness of die-cast AZ91D alloy increases through on-line solution and off-line aging treatment but decreases after off-line solution treatment. By X-ray diffractometry, optical microscopy, differential thermal analysis, scanning electron microscopy and X-ray energy dispersive spectroscopy, it is found that the microstructures of the die-cast AZ91D magnesium alloy before and after on-line solution and off-line aging are similar, consisting of α-Mg and β-Al12Mg17. The precipitation of Al element is prevented by on-line solution so that the effect of solid solution strengthening is enhanced. The β-Al12Mg17 phases precipitate from supersaturated Mg solid solution after off-line aging treatment, and lead to microstructure refinement of AZ91D alloy, so the effect of precipitation hardening is enhanced. The β-Al12Mg17 phases dissolve in the substructure after off-line solution treatment, which leads to that the grain boundary strengthening phase is reduced significantly and the hardness of die cast AZ91D is reduced.

Effect of solution treatment and artificial aging on microstructure and mechanical properties of Al-Cu alloy

In order to achieve good mechanical properties of Al-Cu alloys such as high strength and good toughness,precipitation hardening and artificial aging treatment were applied.As defined by the T6 heat treatment,the standard artificial aging treatment for Al-Cu alloy followed heat treatments of solution treatment at 510-530 ℃ for 2 h,quenching in water at 60 ℃ and then artificial aging at 160-190 ℃ for 2-8 h.The effects of solution treatment and artificial aging on the microstructure and mechanical properties of Al-Cu alloy were studied by optical microscopy（OM）,scanning electron microscopy（SEM）,energy dispersive X-ray spectroscopy（EDS）,transmission electron microscopy（TEM） and tensile test.The results of solution treatment indicate that the mechanical properties of Al-Cu alloy increase and then decrease with the increase of solution temperature.This is because the residual phases dissolve gradually into the matrix,and the fraction of the precipitation and the size of the re-crystallized grain increased.Compared to the solution temperature,the solution holding time has less effect on the microstructure and the mechanical properties of Al-Cu alloy.The artificial aging treatments were conducted at 160-180 ℃ for 2-8 h.The results show that the ultimate tensile strength can be obtained at 180 ℃ for 8 h.Ultimate tensile strength increased with increasing time or temperature.Yield strength was found as the same as the ultimate tensile strength result.

Enhanced strengthening by two-step progressive solution and aging treatment in AM50-4%(Zn,Y) magnesium alloy

AM50-4%(Zn,Y)alloy with a Zn/Y mole ratio of6:1was subjected to thermal analysis,and the results were used for designing a two-step progressive solution treatment process.The effects of solution and aging treatments on the microstructure and mechanical properties of the AM50-4%(Zn,Y)alloy were investigated using OM,XRD,SEM/EDS,TEM,tensile test and hardness test.The experimental results demonstrated that the two-step progressive solution treatment could make theΦandβphases sufficiently dissolve into the matrix which possessed higher supersaturated degree of the dissolved solute compared with the one-step solution treatment.This resulted in a certain enhancement of the precipitation strengthening effect during the subsequent aging process.The precipitation of theФphase had a greater impact on the comprehensive mechanical properties of the alloy thanβphase precipitation when the aging treatment was performed at180℃.The peak aging strength of the AM50-4%(Zn,Y)alloy which was subjected to the two-step progressive solution treatment process(345℃for16h and375℃for6h)was obtained after the aging treatment at180℃for12h.

Effect of solution plus aging heat treatment on microstructural evolution and mechanical properties of near-β titanium alloy

The microstructural evolution, mechanical properties and fracture mechanism of a Ti.5Al.5Mo.5V.3Cr.1Zr (Ti-55531) alloy after solution (760.820℃) plus aging (580.640℃) treatments were investigated. The results show that the volume fraction of the primary α(αp) phase decreases with the increase of solution temperature, and the length of the secondary α phase (αs) decreases while its width increases with the increase of aging temperature. Yield and tensile strengths decrease with the increase of solution temperature, while increase with the increase of aging temperature. A good balance of tensile strength and ductility of the alloy is obtained under solution of 800℃ for 2 h plus aging of 640℃ for 8 h, in which the tensile strength is 1434 MPa and the elongation is 7.7%. The coarsening αs phase makes crack propagation paths deflected and tortuous, which increases the crack propagation resistance and improves the ductility and fracture toughness.

Microstructure and mechanical properties of squeeze-cast Al−5.0Mg−3.0Zn−1.0Cu alloys in solution-treated and aged conditions

The microstructure and mechanical properties at different depths of squeeze-cast,solution-treated and aged Al−5.0Mg−3.0Zn−1.0Cu alloy were investigated.For squeeze-cast alloy,from casting surface to interior,the grain size ofα(Al)matrix and width of T-Mg32(AlZnCu)49 phase increase significantly,while the volume fraction of T phase decreases.The related mechanical properties including ultimate tensile strength(UTS)and elongation decrease from 243.7 MPa and 2.3%to 217.9 MPa and 1.4%,respectively.After solution treatment at 470℃ for 36 h,T phase is dissolved into matrix,and the grain size increases so that the UTS and elongation from surface to interior are respectively reduced from 387.8 MPa and 18.6%to 348.9 MPa and 13.9%.After further peak-aging at 120℃ for 24 h,numerous G.P.II zone andη′phase precipitate in matrix.Consequently,UTS values of the surface and interior increase to 449.5 and 421.4 MPa,while elongation values decrease to 12.5%and 8.1%,respectively.

弹体热成形模具材料成分及性能研究

根据高强度钢弹体热成形模具的服役条件和高温合金的设计原则,设计了以中碳、低Cr、Ni、高W、Mo和多元强化为合金化方向的铁基高温堆焊合金模具材料。运用X-射线衍射分析、金相组织观察和性能测试等手段,探讨了合金成分和热处理工艺对该合金组织及性能的影响。结果表明:该合金经固溶-时效处理获得以奥氏体为基体以及弥散分布的合金碳化物M6C和金属间化合物Laves相等强化相,具有良好的高温力学性能和抗氧化性能,工作温度达700～850℃。

Effect of solution treatment and aging on microstructural evolution and mechanical behavior of NiTi shape memory alloy

As-received nickel-titanium （NiTi） shape memory alloy with a nominal composition of Ni50.9Ti49.1 （mole fraction,%） was subjected to solution treatment at 1123 K for 2 h and subsequent aging for 2 h at 573 K, 723 K and 873 K, respectively. The influence of solution treatment and aging on microstructural evolution and mechanical behavior of NiTi alloy was systematically investigated by transmission electron microscopy （TEM）, high resolution transmission electron microscopy （HRTEM）, scanning electron microscopy （SEM） and compression test. Solution treatment contributes to eliminating the Ti2Ni phase in the as-received NiTi sample, in which the TiC phase is unable to be removed. Solution treatment leads to ordered domain of atomic arrangement in NiTi alloy. In all the aged NiTi samples, the Ni4Ti3 precipitates, the R phase and the B2 austenite coexist in the NiTi matrix at room temperature, while the martensitic twins can be observed in the NiTi samples aged at 873 K. In the NiTi samples aged at 573 and 723 K, the fine and dense Ni4Ti3 precipitates distribute uniformly in the NiTi matrix, and thus they are coherent with the B2 matrix. However, in the NiTi sample aged at 873 K, the Ni4Ti3 precipitates exhibit the very inhomogeneous size, and they are coherent, semi-coherent and incoherent with the B2 matrix. In the case of aging at 723 K, the NiTi sample exhibits the maximum yield strength, where the fine and homogeneous Ni4Ti3 precipitates act as the effective obstacles against the dislocation motion, which results in the maximum critical resolved shear stress for dislocation slip.

Effects of heat treatment on microstructure and mechanical properties of ZA27 alloy

The effects of heat treatment on the microstructure and mechanical properties of ZA27 alloy were studied by X-ray diffraction（XRD）,scanning electron microscopy（SEM） and mechanical characterization.The results indicated that the as-cast microstructure of the alloy was mainly composed of α,decomposed β,η and ε phases.After solid solution treatment at 365 ℃ for 1 h,α and η phases dissolved,and the microstructure of specimen was mainly composed of the supersaturated β phases.The phase decomposition of supersaturated ZA27 alloy is a two-stage phase transformation：the decomposition of the supersaturated β phase at the early stage of aging,and with the increase of aging time,ε phase decomposition through a four-phase transformation：α＋ε→T ＇＋ η.A good combination of high tensile elongation and reasonable strength can be achieved by suitable heat treatments.

Effect of heat treatment on microstructure and mechanical property of extruded 7090/SiC_p composite

The ultra high strength SiC particles （SiCp） reinforced Al-10%Zn-3.6%Mg-1.8%Cu-0.36%Zr-0.15% Ni composite was prepared by spray co-deposition. Microstructures of the extruded and different heat-treated bars were analyzed by transmission electron microscopy （TEM） and energy dispersive spectrometry （EDS）. Grain size of the composites prepared by two-stage solution is smaller than that by single-stage solution. After single-stage solution aging treatment, fine precipitates of both η and AlZnMgCu-rich phase can be found both intragranularly and intergranularly. While after the two-stage solution, an amorphous Si-Cu-Al-O （5 nm） layer appears at the interface. The addition of Ni and Zr modified the influence of the two-stage solution and inhibited the growth of the 7090/SiCp composite grain size. Heat treatments can significantly improve the fracture toughness of the composite. The fracture toughness first decreases then increases with the elongation of the aging time.

生产工艺对砂型铸造铬青铜组织及性能的影响

研究了实际生产过程中的铸造工艺、热处理工艺对砂型铸造铬青铜组织及性能的影响。结果表明,加压-减压铸造工艺下、砂型铸造的铬青铜合金铸态组织致密、成分均匀、含气量少。铬含量为0.86%(质量分数)的产品附铸试样经980℃、50min固溶及480℃×4h时效处理后,可获得良好的综合性能。此时,合金的抗拉强度Rm为375MPa,屈服强度Rp0.2为285MPa,硬度为HB125,导电率达到91.5%IACS以上。

Tailoring AZ91 laminates for combination of strength and ductility

Three types of laminates were designed by alternately stacking AZ91 extruded sheets in different states for extrusion to improve the mechanical properties.The tensile tests revealed that the combination of solid-solution-treated sheets with the aging-treated sheets achieved high tensile strength and ductility,i.e.,ultimate tensile strength of~386 MPa and elongation of~19.8%,respectively.Electron backscatter diffraction(EBSD)and TEM results indicated that the aging-treated layers with more nano-sized precipitates and small grain size provided high strength and reasonable ductility,while the solid-solution-treated layers with low dislocation density facilitated strain hardening.Also,the strong interface bonding between the successive layers played an important role in the enhanced ductility.

Heat treatment of 7xxx series aluminium alloys—Some recent developments

The 7xxx series alloys are heat treatable wrought aluminium alloys based on the Al-Zn-Mg（-Cu） system. They are widely used in high-performance structural aerospace and transportation applications. Apart from compositional, casting and thermo-mechanical processing effects, the balance of properties is also significantly influenced by the way in which the materials are heat-treated. This paper describes the effects of homogenisation, solution treatment, quenching and ageing treatments on the evolution of the microstructure and properties of some important medium to high-strength 7xxx alloys. With a focus on recent work at Monash University, where the whole processing route from homogenisation to final ageing has been studied for thick plate products, it is reported how microstructural features such as dispersoids, coarse constituent particles, fine-scale precipitates, grain structure and grain boundary characteristics can be controlled by heat treatment to achieve improved microstructure-property combinations. In particular, the paper presents methods for dissolving unwanted coarse constituent particles by controlled high- temperature treatments, quench sensitivity evaluations based on a systematic study of continuous cooling precipitation behaviour, and ageing investigations of one-, two- and three-step ageing treatments using experimental and modelling approaches, in each case, the effects on both the microstructure and the resulting properties are discussed.

WE43合金中第二相对腐蚀降解性能的影响

采用显微组织观察、EDS分析、失重实验和电化学测试研究了固溶和固溶-时效WE43合金的腐蚀性能。结果表明,通过热处理改变基体中第二相,可得到不同腐蚀性能,固溶-时效试样经0和6 h浸泡后的腐蚀速率高于固溶处理试样的腐蚀速率,然而在浸泡24h后腐蚀速率低于固溶处理试样。镁合金在腐蚀过程中,腐蚀速率先减小后增大。通过建立数学模型解释第二相对腐蚀性能的影响,以及腐蚀速率随时间改变的原因。