时效温度与时间对6005A铝合金挤压型材显微组织与力学性能的影响(英文)

研究时效时间和时效温度对6005A铝合金显微组织与力学性能的影响,对该铝合金挤压型材进行人工时效实验,时效时间分别为4、8和12h,时效温度分别为150、175和200°C。结果表明:随着时效温度和时间增加,挤压过程形成的粗大Al(Fe,Cr)Si析出相形貌由颗粒状向棒状转变,175°C时亚微米级析出相体积分数最大,200°C时在晶界析出1～3μm左右的AlFeSi相。挤压型材的室温力学性能对时效工艺中的温度参数更加敏感,时效工艺为175°C,4～8h时具有最佳的强度和较稳定的力学性能,抗拉强度与屈服强度分别达到300MPa和270MPa以上。     

Effect of T6-treatments on microstructure and mechanical properties of forged Al-4.4Cu-0.7Mg-0.6Si alloy

Transmission electron microscopy (TEM), scanning electron microscopy (SEM), hardness tests and tensile tests were performed to investigate the effect of aging on microstructure and mechanical properties of forged Al-4.4Cu-0.7Mg-0.6Si alloy. The results show that the alloy exhibits splendid mechanical properties with an ultimate tensile strength of 504 MPa and an elongation of 10.1% after aging at 170 °C for 16 h. With tensile testing temperature increasing to 150 °C, the strength of the alloy declines slightly to 483 MPa. Then, the strength drops quickly when temperature reaches over 200 °C. The high strength of the alloy in peak-aged condition is caused by a considerable amount of θ′ and AlMgSiCu (Q) precipitates. The relatively stable mechanical properties tested below 150 °C are mainly ascribed to the stability of θ′ precipitates. The growth of θ′ and Q precipitates and the generation of θ phase lead to a rapid drop of the strength when temperature is over 150 °C.     

Microstructure Evolution and Mechanical Properties of 2219 Al Alloy During Aging Treatment

Hardness and tensile properties of 2219 Al alloys were tested at various temperature (150, 165, 175 °C) and subjected to T6 temper heat treatment to identify the peak aging time at various temperature. Microstructure evolution and precipitate behavior were analyzed with transmission electron microscope (TEM), differential scanning calorimetry (DSC) and x-ray diffraction (XRD). It is found that the peak aging time is 24 h at 150 °C and does not vary down to 165 °C. When the aging temperature rise to 175 °C, the peak aging time down to 12 h. Considering the strength and elongation, the optimum aging treatment is at 165 °C for 24 h after the solution treatment at 535 °C for 1.5 h. Compared with that of only water-quenched sample, after aged at 165 °C for 24 h, the tensile strength of the 2219 Al alloy increases from 324.5 to 411.8 MPa, yield strength from 168 to 310.8 MPa, respectively. The improvement in the mechanical performance is mainly attributed to the precipitation strengthening of the GP zones, θ″ and θ’ phases.     

Effect of Cu addition on overaging behaviour,room and high temperature tensile and fatigue properties of A357 alloy

The aims of the present work are to evaluate the overaging behaviour of the investigated Cu-enriched alloy and to assess its mechanical behaviour, in terms of the tensile and fatigue strength, at room temperature and at 200 °C, and to correlate the mechanical performance with its microstructure, in particular with the secondary dendrite arm spacing (SDAS). The mechanical tests carried out on the overaged alloy at 200 °C indicate that the addition of about 1.3 wt.% Cu to the A357 alloy enables to maintain ultimate tensile strength and yield strength values close to 210 and 200 MPa, respectively, and fatigue strength at about 100 MPa. Compared to the quaternary (Al−Si−Cu−Mg) alloy C355, the A357−Cu alloy has greater mechanical properties at room temperature and comparable mechanical behaviour in the overaged condition at 200 °C. The microstructural analyses highlight that SDAS affects the mechanical behaviour of the peak-aged A357−Cu alloy at room temperature, while its influence is negligible on the tensile and fatigue properties of the overaged alloy at 200 °C.     

流变轧制AZ91合金的热处理和组织性能调控

本文对连续流变轧制AZ91合金在热处理过程中的组织和力学性能演化进行了研究。热处理后两种析出相在基体中出现：一种是晶界处的非连续析出相,另一种是从过饱和基体中析出的小尺寸连续析出相。随着时效温度升高,原子扩散速度也随之提高,导致更多的析出相生成和长大。合金的维氏硬度和拉伸强度峰值在16小时时效后出现,而合金的延伸率随着时效时间的延长和时效温度的提高呈下降趋势。经过对实验结果的分析,适合提升合金综合力学性能的热处理制度为415°C固溶20小时加220°C时效16小时。经热处理后得到的维氏硬度、拉伸强度和延伸率分别为：99 HV,251 MPa和4.5%,各项性能均显著优于流变轧制态合金。相对于传统成型手段,流变轧制加热处理方法成型的AZ91合金展现了优异且均衡的综合力学性能。     

固溶处理和人工时效对Al-Cu合金显微组织和力学性能的影响(英文)

对Al-Cu合金进行析出强化和人工时效处理以获得优异的力学性能,如高的强度、好的韧性。其热处理工艺条件为:510～530℃固溶处理2h;60℃水淬;160～190℃人工时效2～8h。采用光学显微镜、扫描电镜、能谱分析、透射电镜和拉伸实验对经固溶和人工时效处理的Al-Cu合金的组织和力学性能进行表征。固溶处理实验结果表明,Al-Cu合金的力学性能随着固溶处理温度的升高先增加,然后降低。这是由于Al-Cu合金的残余相逐渐溶解进入基体中,从而导致析出相的数量和再结晶晶粒尺寸不断增加。相较于固溶处理温度,固溶处理时间对Al-Cu合金的影响较小。人工时效处理实验结果表明,合金经180℃时效8h,可以获得最大的拉伸强度。合金的最大拉伸强度和屈服强度随着时效时间的延长和温度的升高而升高。     

Microstructure and mechanical properties of new metastable β type titanium alloy

A new metastable β type titanium alloy called TB-13 with the combination of excellent strength and ductility was developed successfully.In order to develop a perspective on this new alloy,the influence of several commonly used heat treatments on the microstructure and properties was studied.In solution-treated and quenched samples,a low-temperature aging at 480°C results in the precipitation of finerαphase.The precipitation of coarserαphase plate at higher aging temperature(560°C)leads to the increase of tensile ductility but reduction of strength.During low-temperature aging at 300°C,quite homogeneous distribution of fine isothermalωphase particles was found.The isothermalωphase provides nucleation sites forαphase during two-step aging process and makesαphase extremely fine and disperse uniformly in β matrix.Thus,TB-13 alloy is strengthened and its mechanical properties are improved.     

Effect of secondary aging on microstructure and properties of cast Al-Cu-Mg alloy

To obtain better comprehensive properties of cast Al-Cu-Mg alloys, the secondary aging (T6I6) process (including initial aging, interrupted aging and re-aging stages) was optimized by an orthogonal method. The microstructures of the optimized Al-Cu-Mg alloy were observed by means of scanning electron microscopy and transmission electron microscopy, and the properties were investigated by hardness measurements, tensile tests, exfoliation corrosion tests, and intergranular corrosion tests. Results show that the S phase and θ′ phase simultaneously exist in the T6I6 treated alloy. Appropriately increasing the temperature of the interrupted aging in the T6I6 process can improve the mechanical properties and corrosion resistance of Al-Cu-Mg alloy. The optimal comprehensive properties (tensile strength of 443.6 MPa, hardness of 161.6 HV) of the alloy are obtained by initial aging at 180 °C for 2 h, interrupted aging at 90 °C for 30 min, and re-aging at 170 °C for 4 h.

     

Effect of thermal exposure on microstructure and mechanical properties of Al−Si−Cu−Ni−Mg alloy produced by different casting technologies

The effect of thermal exposure at 350 °C for 200 h on microstructure and mechanical properties was investigated for Al−Si−Cu−Ni−Mg alloy, which was produced by permanent mold casting (PMC) and high pressure die casting (HPDC). The SEM and IPP software were used to characterize the morphology of Si phase in the studied alloys. The results show that the thermal exposure provokes spheroidization and coarsening of eutectic Si particles. The ultimate tensile strength of the HPDC alloy after thermal exposure is higher than that of the PMC alloy at room temperature. However, the TEPMC and TEHPDC alloys have similar tensile strength around 67 MPa at 350 °C. Due to the coarsening of eutectic Si, the TEPMC alloy exhibits better creep resistance than the TEHPDC alloy under studied creep conditions. Therefore, the alloys with small size of eutectic Si are not suitably used at 350 °C.     

The superior thermal stability and tensile properties of hot rolled W-HfC alloys

Herein, a W-0.5wt%HfC (WHC05) alloy is fabricated by conventional sintering and multi-step hot-rolling. The high-temperature stability and tensile properties at different temperatures, ranging from room temperature to 600 °C, are studied to demonstrate the influence of HfC addition. The results reveal that the WHC05 alloy has a higher recrystallization temperature (1400 °C–1500 °C) than the previously reported as-rolled pure W (1200 °C) and as-rolled W-0.5wt%ZrC (WZC05 ~ 1300 °C) alloy. Moreover, after recovery and recrystallization (annealing at 1600 °C), the WHC05 alloy maintained a high ultimate tensile strength of ~300 MPa and exhibited a desirable increase in total elongation (>35%), which is ~1.6 times higher than the recrystallized WZC05 at 500 °C. The superior thermal stability and excellent high-temperature mechanical properties can be ascribed to the unique microstructure and uniform dispersion of nano-sized HfC particles in W matrix. The influence of annealing temperature on grain structure, grain orientation and distribution of nano-sized HfC particles has been studied to unveil the possible mechanism of enhanced thermal stability and superior mechanical properties.     

热处理工艺对砂型铸造Al−2Li−2Cu−0.5Mg−0.2Sc−0.2Zr合金显微组织和力学性能的影响

研究不同热处理工艺对砂型铸造Al?2Li?2Cu?0.5Mg?0.2Sc?0.2Zr合金显微组织和力学性能的影响.设计三级固溶处理方案((460℃,32 h)+(520℃,24 h)+(530/540/550℃,4/12/24/32 h))和不同温度(125,175,225℃)时效处理方案用于比较.采用光学显微镜(OM...     

Effects of heat treatment on microstructure and mechanical properties of Mg-6Zn-4Sm-0.4Zr alloy

A new rare earth magnesium alloy(Mg-6 Zn-4 Sm-0.4 Zr, wt.%) was prepared by permanent mould casting. The microstructure and mechanical properties of the alloy sample in as-cast and various heat treatment situations were characterized with an optical microscope(OM), X-ray diffractometer(XRD), scanning electron microscope(SEM) equipped with energy dispersive spectroscope(EDS), transmission electron microscope(TEM) and mechanical tests at room temperature, respectively. The experimental results show that the as-cast alloy mainly consists of α-Mg, eutectic Mg_2Zn_3, MgZnSm and Mg_(41)Sm_5. These eutectic phases with continuous or semicontinuous morphology principally distribute along grain boundaries. Almost all the eutectic compounds dissolve in α-Mg and the grains have no obvious growth trend after optimum solution treatment at 490 °C for 18 h. Meanwhile, the ultimate tensile strength(UTS) of 229 MPa and elongation(EL) to rupture of 9.78% can be achieved through the optimal solution treatment, which increase by 37 MPa and 57.74%, respectively, compared with that of the as-cast alloy. Further aging treatments at 200 °C for different durations lead to the conspicuous increment of mechanical properties and prominent age-hardening response. Peak-aged alloy(treated at 200 °C for 12 h) reveals better mechanical properties(UTS 258 MPa, EL 9.42%, hardness 73.4 HV) compared with the same alloy treated in other aging conditions, which is mainly ascribed to precipitated Mg_2Zn_3 and MgZn_2 phases. Fracture analysis demonstrates that the as-cast alloy belongs to inter-granular and cleavage fracture patterns, while the solutionized alloy(treated at 490 °C for 18 h) reveals trans-granular and quasi-cleavage fracture modes. For the peak-aged alloy, the fracture pattern obeys the mixture of trans-granular and cleavage modes.     

Single-aging characteristics of 7055 aluminum alloy

The microstructures and properties of 7055 aluminum alloy were studied at different single-aging for up to 48 h using hardness test, tensile test, electrical conductivity measurement, XRD and TEM microstructure analysis. The results show that at the early stage of aging, the hardness and strength of the alloy increase rapidly, the peak hardness and strength are approached after 120 ℃ aging for 4 h, then maintained at a high level for a long time. The suitable single-aging treatment of 7055 alloy is 480 ℃, 1 h solution treatment and water quenching, then aging at 120 ℃ for 24 h. Under those condition, the tensile strength, yield strength, elongation and electrical conductivity of the studied alloy are 513 MPa, 462 MPa, 9.5% and 29%（IACS）, respectively. During aging, the solid solution decomposes and precipitation occurs. At the early aging stage of 120 ℃, GP zones form and then grow up gradually with increasing ageing time. η′ phase forms after ageing for 4 h and η phase starts to occur after 24 h aging.     

Effect of non-isothermal aging on microstructure and properties of Al–5.87Zn–2.07Mg–2.42Cu alloys

The evolution of microstructure and properties of Al–5.87Zn–2.07Mg–2.42Cu alloys during non-isothermal aging was studied. The mechanical properties of the alloy were tested by stretching at room temperature. The results show that in the non-isothermal aging process, when the alloy is cooled to 140 °C, the ultimate tensile strength of the alloy reaches a maximum value of 582 MPa and the elongation is 11.9%. The microstructure was tested through a transmission electron microscope, and the experimental results show that the GP zones and η’ phases are the main strengthening precipitates. At the cooling stage, when the temperature dropped to 180 °C, the GP zones were precipitated again. Besides, the experimental results show that the main strengthening phase during non-isothermal aging is η’ phases.     

时效对AEZ611镁合金组织及力学性能的影响

通过对挤压坯预成形AEZ611镁合金进行锻压成形及时效热处理,研究了塑性形变及时效过程中显微组织及力学性能的变化规律。结果表明,在箱式电阻炉中时效处理,晶界较粗且晶粒大小不均,油浴中时效晶界变细,有利于合金力学性能的改善。同时AEZ611镁合金力学性能及显微组织对温度较为敏感。时效温度升高至200℃时,第二相的析出速度加快,且析出相分布变得均匀,细小的黑色点状相弥散分布于晶界上;随着时效保温时间的延长,稀土相Al4Ce相在镁合金的弥散数量增加,且晶粒大小均匀,使合金的力学性能得以进一步改善,稀土的弥散数量、大小及形貌对AEZ611镁合金的力学性能有着重要的影响。最佳时效工艺为油浴中时效390℃×1h+200℃×20h,其抗拉强度可达311MPa,屈服强度达到232MPa,伸长率为11%。     

Effects of extrusion and heat treatments on microstructure and mechanical properties of Mg–8Zn–1Al–0.5Cu–0.5Mn alloy

The effects of extrusion and heat treatments on the microstructure and mechanical properties of Mg–8Zn–1Al–0.5Cu– 0.5Mn magnesium alloy were investigated. Bimodal microstructure is formed in this alloy when it is extruded at 230 and 260 °C, and complete DRX occurs at the extruding temperature of 290 °C. The basal texture of as-extruded alloys is reduced gradually with increasing extrusion temperature due to the larger volume fraction of recrystallized structure at higher temperatures. For the alloy extruded at 290 °C, four different heat treatments routes were investigated. After solution + aging treatments, the grains sizes become larger. Finer and far more densely dispersed precipitates are found in the alloy with solution + double-aging treatments compared with alloy with solution + single-aging treatment. Tensile properties are enhanced remarkably by solution + double-aging treatment with the yield strength, tensile strength and elongation being 298 MPa, 348 MPa and 18%, respectively. This is attributed to the combined effects of fine dynamically recrystallized grains and the uniformly distributed finer precipitates.     

Effect of bonding temperature and heat treatment on microstructure and mechanical property of Mg−6Gd−3Y alloy vacuum diffusion bonded joints

Diffusion bonding of as-cast Mg?6Gd?3Y magnesium alloy was carried out at temperatures of 400?480 °C with bonding pressure of 6 MPa for 90 min. Diffusion bonded joints were solution treated at 495 °C for 14 h and then aged at 200 °C for 30 h. Microstructures and mechanical properties of joints were analyzed. The results showed that rare earth elements and their compounds gathering at bonding interface hindered the grain boundary migration crossing bonding interface. Tensile strength of as-bonded and as-solution treated joints increased firstly and then decreased with the bonding temperature increasing due to the combined effects of grain coarsening and solid-solution strengthening. As-bonded and solution-treated joints fractured at matrix except the joint bonded at 400 °C, while aged joints fractured at bonding interface. The highest ultimate tensile strength of 279 MPa with elongation of 2.8% was found in joint bonded at 440 °C with solution treatment followed by aging treatment.     

Sb对AM50-Y镁合金组织和力学性能的影响

研究合金元素Sb对AM50-Y合金显微组织和力学性能的影响。结果表明,加入Sb后,合金晶粒明显细化,同时形成弥散分布的YSb相。YSb相作为异质形核核心,促进了细小弥散分布的Al2Y颗粒相的形成。随着Sb含量的增加,合金室温和150℃高温抗拉强度、延伸率及室温冲击韧性先上升后下降。当Sb含量为0.6%时,合金综合力学性能最好:合金室温抗拉强度、延伸率和冲击韧性分别为257MPa、9.9%和26J·cm-2,与未添加Sb合金相比分别提高了13.7%、15.9%和14.9%;合金的高温抗拉强度和延伸率达到203MPa和11.9%,分别提高了12.8%和15.5%。     

Interfacial structures and mechanical properties of a high entropy alloy-diamond composite

A FeCoCrNiMo high-entropy alloy (HEA)/diamond composite prepared by spark plasma sintering (SPS) was investigated. Sintering the HEA/diamond composites at different temperatures leads to different interfacial structures, which have an impact on the mechanical properties. The multiple microstructures at HEA/diamond interface have different effects on the retention of the HEA matrix on diamond particles. It was found that the interstitial strengthening effect, amorphous carbon and nano-scale ordered carbon complex were beneficial to the mechanical properties. Due to the good interfacial bonding strength between the HEA matrix and un-failed diamond particles, the composite sintered at 950 °C exhibited an optimized combination of mechanical properties, with a hardness of 630 HV, transverse rupture strength of 1310 MPa, and optimal wear resistance. The failure of the diamond particles and the formation of brittle chromium carbides at sintering temperature at 1000 °C can deteriorate the properties of HEA/diamond composites.     

时效处理对AZ81镁合金组织与力学性能的影响

通过对挤压坯预成形AZ81镁合金进行模压成形及随后的时效处理,研究了形变及时效过程中显微组织及力学性能的变化规律.结果表明:时效温度埘AZ81镁合金力学性能及显微组织的影响较大,随时效温度升高至200℃,第二相的析出速度加快,且析出相分布变得均匀,细小析出相呈弥散状态分布于晶界上;随时效时间的延长.β-Mg17Al12析出相逐渐增多,当时效温度为200℃、时效20h时,晶界大多被析出物所掩盖,晶粒内充满大量点针状析出相,合金显微组织的各向异性得以消除,成分较为均匀,进一步提高了模压成形镁合金的力学性能,经400℃模压成形及200℃×20 h的时效处理后,其抗拉强度可达358.5 MPa,屈服强度达到260.7 MPa,伸长率为9.8%.