Microstructure and mechanical properties of forged AI-7.1Zn-1.1Mg- 1.6Cu-0.14Zr alloy after two-step ageing treatment at 120 and 170℃

The tensile properties, electrical conductivity, and microstructure of the forged Al-7.1Zn-1.1Mg-1.6Cu-0.14Zr alloy were investigated after a two-step ageing treatment at 120 and 170°C. The results indicate that the strength of the alloy reaches the peak value at 170°C for 1 h during the second step ageing and then decreases sharply. However, the electrical conductivity value increases continuously with the second ageing time increasing. The fracture mechanism of the alloy is intergranular fracture for 1 h and then changes to dimple transgranular fracture later, and the toughness of the alloy is improved significantly. The phases of η′ and η are major precipitates in the alloy under the two-step ageing condition. Discontinuous grain boundary precipitates and precipitate-free zones along the grain boundary are clearly observed.     

Precipitation Hardening of Cu-3Ti-1Cd Alloy

Precipitation strengthening of Cu-3Ti-1Cd alloy has been studied using hardness and tensile tests, electrical resistivity measurements, and transmission electron microscopy. The alloy exhibited a hardness of 117 Hv in solution-treated (ST) condition and attained a peak hardness of 288 Hv after aging at 450 °C for 72 h. Electrical conductivity increased from 7%IACS (International Annealed Copper Standard) in ST condition to 13%IACS on aging at 450 °C for 16 h. The alloy exhibited yield strength (YS) of 643 MPa and ultimate tensile strength (UTS) of 785 MPa in peak-aged (PA) condition. Strengthening in Cu-3Ti-1Cd alloy in PA condition is attributed to solid solution strengthening effect of cadmium (Cd) as well as fine scale precipitation of metastable and coherent β′-Cu₄Ti phase. On overaging at 450 or 500 °C, the alloy showed a decrease in hardness as a result of formation of equilibrium precipitate β-Cu₃Ti as continuous precipitation within the matrix and as discontinuous precipitation at the grain boundaries. While the tensile properties are better, the electrical conductivity of Cu-3Ti-1Cd alloy is less than that of binary Cu-2.7Ti alloy. The strengthening mechanism is the same in both binary and ternary alloys of Cu-Ti, i.e., precipitation of metastable and coherent β′-Cu₄Ti phase.     

Microstructure and Precipitate's Characterization of the Cu-Ni-Si-P Alloy

Microstructure of the Cu-Ni-Si-P alloy was investigated by transmission electron microscopy (TEM). The alloy had 551 MPa tensile strength, 226 HV hardness, and 36% IACS electrical conductivity after 80% cold rolling and aging at 450 °C for 2 h. Under the same aging conditions, but without the cold rolling, the strength, hardness, and electrical conductivity were 379 MPa, 216 HV, and 32% IACS, respectively. The precipitates identified by TEM characterization were δ-Ni₂Si. Some semi-coherent spherical precipitates with a typical coffee bean contrast were found after aging for 48 h at 450 °C. The average diameter of the observed semi-coherent precipitates is about 5 nm. The morphology of the fracture surface was observed by scanning electron microscopy. All samples showed typical ductile fracture. The addition of P refined the grain size and increased the nucleation rate of the precipitates. The precipitated phase coarsening was inhibited by the small additions of P. After aging, the Cu-Ni-Si-P alloy can gain excellent mechanical properties with 804 MPa strength and 49% IACS conductivity. This study aimed to optimize processing conditions of the Cu-Ni-Si-P alloys.     

Corrosion behavior of novel Cu–Ni–Al–Si alloy with super-high strength in 3.5% NaCl solution

A novel Cu–6.5Ni–1Al–1Si–0.15Mg–0.15Ce alloy with super-high strength was designed and its corrosion behavior in 3.5% NaCl solution at 25 °C was investigated by the means of SEM observation, TEM observation and XPS analysis. The alloy after solution treatment, 80% cold rolling and aging at 450 °C for 1 h had the best comprehensive properties with hardness of HV 314, electrical conductivity of 19.4% IACS, tensile strength of 1017 MPa, and average annual corrosion rate of 0.028 mm/a. The oxides and chloride products formed at first, followed by the formation of dyroxides products. The alloy showed super-high strength, good electrical conductivity and corrosion resistant because Ni₂Si hindered the precipitation of large NiAl at the grain boundary and the denickelefication of the alloy.     

时效时间对7150铝合金组织和性能的影响

通过维氏硬度测试、电导率测试和拉伸、晶间腐蚀等测试方法,研究了预时效、回归及再时效三个阶段中的时效时间对7150铝合金组织和性能的影响,借助透射电镜观察时效处理各阶段合金的微观组织演变。结果表明:120℃×20 h欠时效作为预时效工艺,比120℃×24 h峰时效的晶内析出相更细小,高温回归时更利于回溶。在190℃短时回归5、15和30 min中,15 min回溶效果最好,硬度最低,再经120℃×24 h再时效后合金抗拉强度Rm、屈服强度RP0.2、伸长率A分别为622 MPa、573 MPa、10.8%,显微硬度为204 HV,力学性能与120℃×24 h单级峰时效时相近。经120℃×20 h+190℃×15 min+120℃×24 h处理后7150铝合金综合性能好,耐晶间腐蚀性能佳。     

一种新型Al-Zn-Mg-Cu高强铝合金的析出行为及性能(英文)

对一种新型高强Al-Zn-Mg-Cu合金在单级时效过程中的硬度、强度、电导率变化及相应的析出行为进行系统的研究。结果表明,电导率随着时效温度的升高和时效时间的延长而不断增高。在时效开始阶段,硬度和强度随着时效的进行迅速升高并达到峰值。在120°C时效时,硬度和强度到达峰值后保持稳定,主要的析出相是GPI区、GPII区和η′相。在120°C长时间(直至24h)时效后,GPI区和GPII区仍能稳定存在。在160°C时效时,硬度和强度到达峰值后迅速下降。与120°C时效相比,在160°C时效时,析出过程更快。在160°C时效1h后,未观察到GPI区及GPII区的存在,主要的析出相为η′相。在160°C时效24h后,主要的析出相为η相。     

Optimization of conductivity and strength in Cu-Ni-Si alloys by suppressing discontinuous precipitation

Cu-Ni-Si alloys with and without Ti were solution treated at 980 °C for 1 h and cooled by air cooling and water quenching, after which the specimens were aged at 500 °C. The two alloys showed different aging characteristics with different cooling rates during the aging process. The conductivity of all alloys increased during aging; for alloys that were water quenched, hardness increased at the early stage of aging and then drastically decreased. The air-cooled Cu-Ni-Si alloy without Ti also experienced an increase in hardness, which then decreased during aging, but the air-cooled Cu-Ni-Si alloy with Ti did not show a drastic decrease in hardness during prolonged aging. A combination of yield strength and conductivity of 820 MPa and 42% IACS, respectively, was achieved in the air-cooled Cu-Ni-Si-Ti alloy after solution treatment.     

缓慢升温时效处理对Al-Zn-Mg-Er-Zr合金性能的影响

利用扫描电镜(SEM)、显微硬度计及电导仪研究了120℃时效的两种不同工艺对Al-5Zn-3Mg-0.1Er-0.1Zr合金力学性能及导电率的影响。结果表明,相较于直接置于120℃时效工艺,采用5 h缓慢升温至120℃时效处理的试验合金的导电率提高至30.77%IACS,硬度、抗拉强度、屈服强度和伸长率分别提升至186.6 HV0.2、538 MPa、454 MPa和17.5%。两种时效工艺处理合金的断裂方式均为韧脆混合型断裂,但5 h缓慢升温时效处理合金的韧窝密度较高,剪切面特征减少。     

扩展路径低温ECAP及时效热处理对Cu0.6Cr合金的组织和性能影响

采用光学显微镜和X射线衍射仪对Cu0.6Cr合金经低温扩展路径等通道转角挤压（ECAP）后的组织演变规律进行了研究。采用扫描电子显微镜和能谱仪研究了Cu0.6Cr合金经不同时效热处理条件后的晶粒大小、析出相分布规律和断裂特征。并且分别测试了合金经低温ECAP和低温ECAP+时效热处理后的抗拉伸强度、硬度和导电率。结果表明,Cu0.6Cr合金经低温ECAP变形后形成明显细化且相互交割的纤维组织,并且合金在变形中始终保持（111）面的择优取向。时效热处理的合金变形量越大,析出相的数目和尺寸就越大,第二相析出速率也越快。5道次合金经450 ℃时效2 h后的抗拉伸强度为568.1 MPa,维氏硬度为1624.8 MPa,导电率为82%IACS。     

Effect of thermomechanical treatment on microstructure and properties of Cu-Cr-Zr-Ag alloy

The effects of thermomechanical treatment on the properties and microstructure of Cu-Cr-Zr alloy and Cu-Cr-Zr-Ag alloy were investigated. Ag addition improves the mechanical properties of the alloy through solid solution strengthening and brings a little effect on the electrical conductivity of the alloy. A new Cu-Cr-Zr-Ag alloy was developed, which has an excellent combination of the tensile strength, elongation, and electrical conductivity reaching 476.09 MPa, 15.43% and 88.68% IACS respectively when subjected to the optimum thermomechanical treatment, i.e., solution-treating at 920°C for 1 h, cold drawing to 96% deformation, followed by aging at 400°C for 3 h. TEM analysis re-vealed two kinds of finely dispersed precipitates of Cr and Cu4Zr. It is very important to use the mechanisms of solid solution strengthening, work hardening effect as well as precipitate pinning effect of dislocations to improve tensile strength of the alloy without adversely affecting its electrical conductivity.     

Retrogression and re-aging treatment of Al-9.99%Zn-1.72%Cu-2.5%Mg-0.13%Zr aluminum alloy

1 Introduction The 7000 series aluminum alloys have been widely used as aircraft structure material because of their high strength/density ratio. This series of alloys provide high strength in the T6 condition but are prone to stress corrosion cracking(SC…     

Effect of cryorolling on microstructure and property of high strength and high conductivity Cu−0.5wt.%Cr alloy

Cu−0.5wt.%Cr alloy with high strength and high conductivity was processed by cryorolling (CR) and room temperature rolling (RTR), respectively. The microstructure, mechanical property and electrical conductivity of Cu−0.5Cr alloy after CR/RTR and aging treatment were investigated. The results indicate that obvious dislocation entanglement can be observed in matrix of CR alloy. The Cr particles in the alloy after CR and aging treatment possess finer particle size and exhibit dispersive distribution. The peak hardness of CR alloy is HV 167.4, significantly higher than that of RTR alloy. The optimum mechanical property of CR alloy is obtained after aging at 450 °C for 120 min. The conductivity of CR Cu−0.5Cr alloy reaches 92.5% IACS after aging at 450 °C for 120 min, which is slightly higher than that of RTR alloy.     

Aging characteristic of Cu-0.6Cr-0.15Zr-0.05Mg-0.02Si alloy containing trace rare earth yttrium

The aging characteristic of Cu-0.6Cr-0.15Zr-0.05Mg-0.02Si alloy containing trace rare earth yttrium was investigated. The results showed that Cu-0.6Cr-0.15Zr-0.05Mg-0.02Si alloy obtained good comprehensive performance after 80% rolling and then aging at 480℃ for 1 h; the hardness and electrical conductivity reached HV 150 and 85.5% IACS, respectively. Increasing aging temperature accelerated aging precipitation. The time for attaining peak hardness was postponed, the precipitates were finer (2-4 nm), and the interparticle spacing was shorter due to yttrium addition. The hardness and electrical conductivity of the Y-containing alloy after 80% deformation and then aging at 480℃ for 45 min reached HV 174 and 82.1% IACS, respectively.     

喷射成形7055高强铝合金的热处理工艺优化及其应用

基于两次挤压处理后的喷射成形7055铝合金,采用SEM、光学显微镜、硬度仪和拉伸试验机等分析手段研究了试验合金在不同时效工艺下的组织和性能。结果表明,相较于单级时效工艺,经过120 ℃×6 h+160 ℃×2 h双级时效处理后,析出相呈短棒状均匀分布于基体,其沿长度方向上的平均尺寸为500 nm,宽度方向平均尺寸为10 nm,时效峰值硬度达196.4 HV0.05。采用双级时效工艺处理的试验合金在298、398、498和598 K的抗拉强度分别为855、792、688和360 MPa,断后伸长率分别为14%、11%、9%和8%。采用该双级时效处理工艺处理的喷射成形7055铝合金应用于轮毂紧固件产品的制备,并对其进行硫酸阳极氧化处理,可使得紧固件试样同时兼具高强度、高硬度以及高耐蚀性能,有望得到更广泛的应用。     

新型Al-Zn-Mg-Cu合金型材回归再时效处理的组织与性能

采用拉伸、硬度、电导率测试和透射电镜分析等方法研究了不同回归处理工艺对Al-Zn-Mg-Cu合金型材组织与性能的影响。结果表明,采用120℃×24 h+180℃×45 min+120℃×24 h回归再时效处理后,合金的抗拉强度、屈服强度、伸长率和电导率分别为613.5 MPa、599 MPa、11.1%和39.2%IASC。与T6态相比,合金在抗拉强度和伸长率相当的情况下,屈服强度和电导率显著提高,合金的抗应力腐蚀性能明显改善。合金晶内为细小的η’相和η相,晶界沉淀相断续分布,伴有较窄的晶界无析出带。     

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 and properties characteristic during interrupted multi-step aging in Al-Cu-Mg-Ag-Zr alloy

The effects of interrupted multi-step aging on the microstructure and properties of Al-Cu-Mg-Ag-Zr alloy were studied by tensile,hardness,electrical conductivity tests and transmission electron microscopy(TEM).Interrupted multi-step aging delayed the peak aging time compared to one-step aging and kept the same levels of hardness,electrical conductivity,ultimate tensile strength(UTS),yield strength(YS) and elongation as those of the T6 temper alloy while increased the fracture toughness notably.Ω phase and a little θ’ phase precipitated and grew simultaneously in the process of one-step aging at 160℃.During the second-step aging at 65℃ of interrupted multi-step aging,no TEM characteristic of Ω precipitates could be found.During the third step of interrupted multi-step aging,Ω began to dominate the microstructure like what happened in the process of one-step aging.The difference of properties between the T6 temper and the interrupted multi-step aged alloys might be related to the different precipitation sequences in the process of the two heat treatment technologies.     

快速获得7055铝合金淬火敏感温度区间的新方法及机理（英文）

采用一种省时、节约资源的变温热处理(ATHT)新方法，基于硬度与电导率，获得喷射沉积7055铝合金的淬火敏感温度区间。此外，通过透射电子显微镜(TEM)表征ATHT期间的显微组织演变。研究表明，7055合金的ATHT是一个溶质原子随着温度的升高而析出和再溶解的过程。当温度达到200℃时，合金的硬度急剧增加，电导率适当增加。随着温度升高到400℃以上，电导率从峰值迅速下降，表明溶质原子回溶加速，同时，在基体内η’强化相逐渐转变成η平衡相。通过对硬度曲线和电导率曲线的分析，得出当前合金淬火敏感性温度范围为200～400℃，这与传统分级保温法测得的结果一致。     

CuCo2Be合金的热处理工艺及组织与性能研究

借助布氏硬度计、万能试验机、涡流导电仪、金相显微镜、扫描电镜、能谱仪和X射线衍射分析仪,研究了CuCo2Be合金不同热处理后的组织和性能、物相及组分。结果表明,CuCo2Be合金的最佳热处理工艺为950℃×1.5 h固溶+460℃×1.5 h时效,硬度和导电率达到较好的匹配。布氏硬度为254 HBS、导电率为47.24%IACS、抗拉强度为880.56 MPa;未固溶相主要为Co0.52Cu0.48、Cu6.69Si和Be2Cu,时效析出相可能为BeCo、Be2Cu和Co0.52Cu0.48。     

Enhanced Strength in Cu-Ag-Zr Alloy by Combination of Cold Working and Aging

In this investigation, the effect of different degree of cold rolling and post-aging treatment on the microstructure and mechanical properties of a Cu-3wt.%Ag-0.5wt.%Zr alloy was studied by means of hardness measurement, tensile tests, optical and electron microscopy. The alloy was subjected to cold rolling up to 80% followed by aging in the temperature range of 400-500 °C. The yield strength, ultimate tensile strength and hardness were found to increase as degree of cold rolling increased, but at the expense of ductility. Aging of cold rolled samples in the studied temperature range has resulted in different combinations of strength and ductility. However, aging of cold rolled samples at 400 °C for 1 h has resulted in a combination of high strength and moderate ductility. A yield strength and ultimate tensile strength of 511 and 560 MPa, respectively with a ductility of 12% were achieved for 80% cold rolled and aged (400 °C for 1 h) sample. The high strength achieved after 80% cold rolling and aging is mainly attributed to precipitation of fine silver precipitates.