ZTM630镁合金双级时效实验研究

通过改变Mg-6Zn-3Sn-0.5Mn合金终时效时间,利用金相显微镜、扫描显微镜、透射电子显微镜观察挤压态ZTM630合金在双级时效后的微观组织特征。结果表明,该合金比较适宜的双级时效参数为90 ℃×12 h+180 ℃×8 h,在该参数下合金的抗拉强度、伸长率分别为383.1 MPa、7.667%。双级时效之后,在基体与晶界处都有弥散细小的析出相析出,主要为Mg2Sn、MgZn2相化合物。在拉伸过程中弥散细小析出相的析出强化作用和阻碍晶粒移动产生的强化作用,使得合金的力学性能更优。     

淬火转移时间对A357 铝合金力学性能与微观组织的影响

 采用OM、DSC、SEM 与TEM,结合力学性能测试研究淬火转移时间对A357 铝合金力学性能与微观组织的影响。结果表明:随着淬火转移时间由3 s 延长至49 s,A357 铝合金经T6 热处理后的抗拉强度、屈服强度与延伸率分别由351 MPa、275MPa 与12.4%降低至320 MPa、254 MPa 与6.5%,合金材料的抗拉强度连续下降,屈服强度变化较小,延伸率呈现出先上升后下降的变化趋势。初生与共晶Si 相逐渐由细长的针状或片层状转变为椭圆球状或棒状,平均长度为10~25 μm,平均宽度为5~10 μm,当淬火转移时间超过35 s 后,初生与共晶Si 相则仍以细长的针状或片层状形貌为主。拉伸断口形貌以韧窝断裂为主,附带部分沿晶断裂,随着淬火转移时间的增加,断口表面韧窝数量随之减少,沿晶断裂裂纹数量不断增加;Mg 与Si 元素集中分布于晶粒边界处的二元与三元共晶组织中,Al 元素广泛分布于晶粒内部及晶粒边界处;人工时效过程析出的Mg₂Si 强化相长度约为0.2~1 μm,宽度为0.02~0.08 μm,且随着淬火转移时间的延长,Mg₂Si 强化相的析出数大量减少,长径比不断下降,合金材料的强度与塑性随之降低。     

深冷处理对Inconel 617合金组织和力学性能的影响

深冷处理方法由于操作简单,价格低廉且对材料性能改善明显目前被广泛应用.采用深冷处理方法对Inconel 617合金进行了不同处理时间和次数条件下的试验.利用扫描电子显微镜(SEM)、电子背散射衍射(EBSD)、透射电子显微镜(TEM)分析了Inconel 617合金的微观组织结构,采用万能拉力试验机进行了室温下的拉伸试验.结果表明:深冷处理后Inconel 617合金的晶粒尺寸得到了细化.单次深冷处理12、24 h后合金的小角度晶界分数增大,这有助于合金拉伸强度和塑性的提高.但是深冷处理后合金中析出了大量的碳化物,降低了其强度.     

时效对形变Cu-Zr-Si合金组织及性能的影响

采用等径角挤压(ECAP)技术对Cu-0.16Zr-0.04Si合金在室温和液氮低温下进行1道次变形,随后在450 ℃下时效4 h.通过扫描电子显微镜(SEM)和X射线能谱仪(EDS)等技术,研究时效对合金变形组织的影响,分析了合金力学性能和导电性能的变化.结果表明:合金在变形及时效后,晶界处出现不均匀分布的棒状或颗粒状析出相,基体中出现弥散分布的细小点状析出相;合金的抗拉强度和导电率在变形时效处理后得到同步提高;随着时效时间的延长,合金的断裂韧性逐渐变差.     

Preparation of high-strength Al-Mg-Si-Cu-Fe alloy via heat treatment and rolling

An Al-Mg-Si-Cu-Fe alloy was solid-solution treated at 560°C for 3 h and then cooled by water quenching or furnace cooling. The alloy samples which underwent cooling by these two methods were rolled at different temperatures. The microstructure and mechanical properties of the rolled alloys were investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis, and tensile testing. For the water-quenched alloys, the peak tensile strength and elongation occurred at a rolling temperature of 180°C. For the furnace-cooled alloys, the tensile strength decreased initially, until the rolling temperature of 420°C, and then increased; the elongation increased consistently with increasing rolling temperature. The effects of grain boundary hardening and dislocation hardening on the mechanical properties of these rolled alloys decreased with increases in rolling temperature. The mechanical properties of the 180°C rolling water-quenched alloy were also improved by the presence of β″ phase. Above 420°C, the effect of solid-solution hardening on the mechanical properties of the rolled alloys increased with increases in rolling temperature.     

喷射成形高锌Al-Zn-Mg-Cu合金的时效行为

系统研究了喷射成形高锌Al-Zn-Mg-Cu合金在不同时效处理条件下的显微组织与力学性能.结果表明:自然时效合金在晶界处已析出强化相;单级时效合金随时效时间的延长,晶内和晶界析出相逐渐粗化;双级时效合金的析出相进一步粗化,并且晶界析出相为断续特征;回归再时效合金具有较细的晶内组织及类似于双级时效的晶界组织.同时发现,双级时效合金的抗拉强度比峰时效合金的强度下降了13%左右,而回归再时效合金的强度优于峰时效合金的强度.     

固溶时效处理对Ni50Ti44Al6合金微观组织和力学性能的影响

采用扫描电子显微镜、X射线衍射、室温和高温压缩试验等方法研究了固溶时效对Ni50Ti44Al6合金微观组织和力学性能的影响.Ni50Ti44Al6合金的铸态微观组织是由NiTi基体和沿晶界分布的网状组织构成.随着固溶温度升高,合金中的网状组织部分消失,第二相在基体中趋向于均匀的弥散分布;随时效时间延长,合金的强度先升高后降低.固溶时效处理能有效改善Ni50Ti44Al6合金的力学性能.最佳的处理制度为:合金在1150℃固溶6 h,水淬,再在700℃时效6 h.     

Effect of Sc addition on microstructure and mechanical properties of 1460 alloy

The effect of minor addition of Sc on microstructure,age hardening behavior,tensile properties and fracture morphology of 1460 alloy have been studied. It is found that Sc content increase from 0.11 wt% to 0.22 wt% is favorable for grain refinement in as-cast alloy but results in a coarsening of Cu-rich particles. The alloy with 0.11 wt% Sc exhibits enhanced mechanical properties and age hardening effect. Transmission electron microscopy(TEM) investigations on the alloy with 0.11 wt% Sc have suggested that a large amount of Al3(Sc,Zr) particles precipitated at the earlier aging may inhibit recrystallization effectively.     

Improved strength and ductility of high alloy containing Al-12Zn-3Mg-2.5Cu alloy by combining non-isothermal step rolling and cold rolling

Al-12Zn-3Mg-2.5Cu alloy was prepared using a liquid metallurgy route under the optimized conditions. A sample cut from the ingot was rolled non-isothermally from 400℃ to 100℃ in 100℃ steps, with 15% reduction in thickness; it was then cold rolled isothermally at room temperature for 85% reduction. The cold-rolled alloys were characterized by electron microscopy, hardness test, and tensile test to elucidate their structural evolution and evaluate their mechanical behavior. In the results, the cast alloy consists of α-aluminum and various intermetallic compounds. These compounds are segregated along the grain boundaries, which makes the alloy difficult to roll at room temperature. The combined effect of non-isothermal step rolling and cold rolling results in the nano/microsized compounds distributed uniformly in the matrix. The hardness is substantially increased after rolling. This increase in hardness is attributed to the ultra-fine grain size, fine-scale intermetallic compounds, and structural defects (e.g., dislocations, stacking faults, and sub-grains). The ultimate tensile strength of the rolled alloy is approximately 628 MPa with 7% ductility.     

超声波功率对铸轧5182铝合金带坯组织性能的影响

采用超声波连续铸轧工艺制备5182铝合金带坯,研究了超声波功率对5182铝合金带坯组织性能的影响.结果表明：施加超声波振动可细化5182铝合金带坯的晶粒组织,减轻元素的偏析程度.超声波的功率越大,5182铝合金带坯的晶粒越细小,元素偏析程度越小,拉伸力学性能越高.当超声波功率为800 W时,5182铝合金带坯的抗拉强度为211.4 MPa,伸长率为18.4%,与未施加超声波振动相比,此时5182铝合金带坯的抗拉强度提高了15.8%,伸长率提高了26.0%.     

Effect of cold rolling process on microstructure and mechanical properties of high strength β titanium alloy thin sheets

The microstructure and mechanical properties of Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe high strength titanium alloy sheets prepared by unidirectional cold rolling and two-step cross cold rolling were investigated. Results showed that the β phase grains were refined significantly by cold rolling followed by solution treatment for a short time.Compared to unidirectional cold rolling, the short time solution treatment after two-step cross rolling could significantly reduce the non-uniformity of the microstructure of the alloy sheets. After aging treatment at 550 ℃,the anisotropy of the mechanical properties still existed in the unidirectional rolled sheets, and the tensile strength was highest along the rolling direction. After solution and aging treatment, the anisotropy of the mechanical properties of the two-step cross rolling process sheet was not obvious than unidirectional cold rolling,and alloy had good strength and plasticity matching.     

Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels

Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels were studied.To investigate the microstructure and mechanical properties,optical microscopy,scanning electron microscopy,X-ray diffraction,tensile test,and hardness test were used.The results show that the solution-annealing treatment in the cold-rolled steel redounds to the formation of sub-microcrystalline Fe2(Mo,Ti) Laves phase particles,which are stable at high temperatures.These secondary Laves phase particles prevent from recrystallization at high temperatures and correspond to semi-brittle fracture in the subsequent aging treatment.     

Semisolid die forging process,microstructures and properties of AZ31 magnesium alloy mobile telephone shells

A semisolid slurry of AZ31 magnesium alloy was prepared by vibrating wavelike sloping plate process,and the semisolid die forging process,microstructures,and properties of the magnesium alloy mobile telephone shell were investigated.The semisolid forging process was performed on a YA32-315 four-column universal hydraulic press.The microstructures were observed by optical microscopy,the hardness was analyzed with a model 450SVD Vickers hardometer,the mechanical properties was measured with a CMT5105 tensile test machine,and the fractograph of elongated specimens was observed by scanning electron microscopy (SEM).The results reveal that with the increase of die forging force,the microstructures of the product become fine and dense.A lower preheating temperature and a longer dwell time are favorable to the formation of fine and dense microstructures.The optimum process conditions of preparing mobile telephone shells with excellent surface quality and microstructures are a die forging force of 2000 kN,a die preheating temperature of 250℃,and a dwell time of 240 s.After solution treatment at 430℃ and aging at 220℃ for 8 h,the Vickers hardness is 61.7 and the ultimate tensile strength of the product is 193MPa.Tensile fractographs show the mixing mechanisms of quasi-cleavage fracture and ductile fracture.     

Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels

Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels were studied. To investigate the microstructure and mechanical properties, optical microscopy, scanning electron microscopy, X-ray diffraction, tensile test, and hardness test were used. The results show that the solution-annealing treatment in the cold-rolled steel redounds to the formation of submicrocrystalline Fe₂(Mo, Ti) Laves phase particles, which are stable at high temperatures. These secondary Laves phase particles prevent from recrystallization at high temperatures and correspond to semi-brittle fracture in the subsequent aging treatment.     

Semisolid die forging process,microstructures and properties of AZ31 magnesium alloy mobile telephone shells

A semisolid slurry of AZ31 magnesium alloy was prepared by vibrating wavelike sloping plate process, and the semisolid die forging process, microstructures, and properties of the magnesium alloy mobile telephone shell were investigated. The semisolid forging process was performed on a YA32-315 four-column universal hydraulic press. The microstructures were observed by optical microscopy, the hardness was analyzed with a model 450SVD Vickers hardometer, the mechanical properties was measured with a CMT5105 tensile test machine, and the fractograph of elongated specimens was observed by scanning electron microscopy (SEM). The results reveal that with the increase of die forging force, the microstructures of the product become fine and dense. A lower preheating temperature and a longer dwell time are favorable to the formation of fine and dense microstructures. The optimum process conditions of preparing mobile telephone shells with excellent surface quality and microstructures are a die forging force of 2000 kN, a die preheating temperature of 250℃, and a dwell time of 240 s. After solution treatment at 430℃ and aging at 220℃ for 8 h, the Vickers hardness is 61.7 and the ultimate tensile strength of the product is 193 MPa. Tensile fractographs show the mixing mechanisms of quasi-cleavage fracture and ductile fracture.     

Microstructure evolution and mechanical properties of a large-sized ingot of Mg-9Gd-3Y-1.5Zn-0.5Zr (wt%) alloy after a lower-temperature homogenization treatment

In this paper, a large-sized ingot of Mg-9Gd-3Y-1.5Zn-0.5Zr (wt%) alloy with a diameter of 600 mm was successfully prepared by the semi-continuous casting method. The alloy was subsequently annealed at a relatively low temperature of 430℃ for 12 h as a homogenization treatment. The microstructure and room-temperature mechanical properties of the alloy were investigated systematically. The results show that the as-cast alloy contained a mass of discontinuous lamellar-shaped 18R long-period stacking ordered (LPSO) phases with a composition of Mg₁₀ZnY and an α-Mg matrix, along with net-shaped Mg₅(Y,Gd) eutectic compounds at the grain boundaries. Most of the eutectic compounds dissolved after the homogenization treatment. Moreover, the amount and dimensions of the lamellar-shaped LPSO phase obviously increased after the homogenization treatment. The structure of the phase transformed into 14H-type LPSO with composition Mg₁₂Zn(Y,Gd). The mechanical properties of the heat-treated large-sized alloy ingot are uniform. The ultimate tensile strength (UTS) and tensile yield strength (TYS) of the alloy reached 207.2 MPa and 134.8 MPa, respectively, and the elongation was 3.4%. The high performances of the large-sized alloy ingot after the homogenization treatment is attributed to the strengthening of the α-Mg solid solution and to the plentiful LPSO phase distributed over the α-Mg matrix.     

Effect of long-term aging treatment on the tensile strength and ductility of GH 605 superalloy

Aging treatment is an effective way to optimize the mechanical properties of Co-based superalloys. In this study, commercial GH 605 superalloy was subjected to aging treatment at 650 ?°C in a wide time range up to 1000 ?h. The effects of aging time on the tensile characteristics, microstructure evolution and mechanical properties were systematically investigated at room temperature (RT) and 900 ?°C. The results showed that the volume fractions of M₆C and M₂₃C₆ carbide increased with the aging time. After long-term aging treatment, the yield strength (YS) at RT was enhanced from 490.3 ?MPa to 805.9 ?MPa, while the alloy still had high tensile ductility (above 20%). Microscopic observations by transmission electron microscopy (TEM) indicated that the strengthening mechanism was related to carbide precipitation inside the grains and the change in the dislocation slipping mode. Moreover, long-term aging treatment can increase the elongation from 24.1% to 47.3% at 900 ?°C accompanied by a slight increase of YS from 299.3 ?MPa to 313.9 ?MPa. Based on detailed microstructure analysis the strengthening mechanism can be attributed to the refined grains as well as carbide precipitation inside the grains and around the grain boundaries.     

3003铝合金铸锭均匀化退火工艺及力学性能

为了节能减排,利用光学显微镜、扫描电镜、万能力学试验机等手段,研究分析了3003铝合金不同均匀化退火工艺后的组织演变及力学性能变化。结果表明:随均匀化退火温度的升高,对应的最佳工艺时间减少;620℃下退火5 h时的组织与610℃下退火7 h时基本相同,晶界处无偏析第二相粒子且晶内弥散分布第二相粒子;常温及高温瞬时拉伸时,620℃退火5 h的合金拉伸强度、延伸率均高于610℃退火7 h的。该研究通过升高退火温度、减少时间改善了3003合金铸锭均匀化退火工艺,最佳工艺为650℃下保温5 h。     

Influence of semisolid forging ratio on the microstructure and mechanical properties of Ti14 alloy

The present work is focused on the microstructure and mechanical properties of Ti14 alloy with different semisolid deformation ratios during forging tests. The results revealed that the forging ratio had a significant effect on the precipitation of the alloy. Fewer plate-shaped Ti₂Cu tended to precipitate on grain boundaries with higher forging ratios, and finally the plate-shaped Ti₂Cu formed precipitate-free zones along grain boundaries with a forging ratio of 75%. The precipitation on grain boundaries was found to be controlled by a peritectic reaction. Large forging ratios accelerated the extrusion of liquid and resulted in less liquid along the prior grain boundaries, which reduced the peritectic precipitation in this region and formed precipitate-free zones during re-solidification. In addition, increasing the forging ratio could accelerate dynamic recrystallization, which is favorable for improving the semisolid formability. The tensile ductility increased with increasing forging ratio, and a mixed fracture mode, involving both cleavage and dimple fracture, was observed after forging with a forging ratio of 75%, which is attributed to the presence of precipitate-free zones formed along grain boundaries during semisolid processing.     

Effect of heat treatment on microstructures and properties of a novel Al-Zn-Mg-Cu alloy for oil drilling

In view of the special requirements for strength, heat resistance and corrosion resistance of Al-Zn-Mg-Cu alloy for oil drilling, the Al-6.2 Zn-2.5 Mg-1.6 Cu alloy was prepared by increasing Cu content on basis of Russian Series 1953 alloy. The effect of heat treatment on the microstructures and properties of the alloy was characterized by optical microscope(OM), scanning electron microscope(SEM) and transmission electron microscope(TEM), and investigated by tensile test at room temperature, thermal exposure test and corrosion test. The results show that the strength after T6 aging treatment exhibit a decrease trend as an increase of the solution temperature from465 °C to 480 °C. After the solution treated by the rate of 470 °C/1 h, second phases dissolve into the matrix very well and the strength property reaches optimum. The alloy has better comprehensive properties treated by a solution treatment of 470 °C/1 h and then followed by an aging treatment of 120 °C/24 h + 170 °C/1 h + 120 °C/24 h. Under the aging state, the precipitated phases inside the grains are suitable in size, while on the grain boundary distribute discontinuously and the precipitate-free zone is obvious. Besides, the alloy still maintain high tensile properties. The yield strength, tensile strength and elongation are 650 MPa, 686 MPa,12.0%, respectively. The yield strength retention after heat exposure is 92%. The alloy has good corrosion resistance and the exfoliation corrosion degree. The average corrosion rate in the H_2S and CO_2 environment is 0.0024 mm/a, which is far less than the required 0.12 mm/a. It is insensitive to H_2S and CO_2 environments.