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.     

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.     

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.     

Cu-Cr-Zr-Sn合金的时效析出行为与性能

采用TEM对Cu-0.22Cr-0.05Zr-0.05Sn合金不同形变热处理状态微观组织的演变以及时效过程中析出相的状态进行研究,并以此解释形变热处理过程中合金力学性能和导电性能的变化.结果表明,合金中存在2种析出相,分别是Cr相和Cu4Zr相.其中Cr相在时效过程中分别经历了固溶体、GP区、脱溶并与基体共格以及长大;而Cu4Zr相则以早期Cr析出相为核伴随析出,与基体半共格.由于析出相尺寸很小,且分布较为均匀,使合金具有很强的时效强化效果,经940℃固溶1h后冷加工至变形率为96％并在400℃时效4h,合金的抗拉强度和电导率可分别达到400 MPa和84％IACS.对于该合金,时效温度是决定合金综合性能的关键,而时效时间对综合性能的影响并不显著.     

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…     

Precipitation process and its effects on properties of aging Cu–Ni–Be alloy

The precipitation process of aged Cu-Ni-Be alloy was investigated by X-ray diffraction （XRD）, trans- mission electron microscopy （TEM）, and high-resolution transmission electron microscopy （HRTEM）. The tensile strength, yield strength, and electronic conductivity of this alloy after aging were also studied. The precipitation sequence of the C17510 alloy aged at 525 ℃ is supersat-urated solid solution→G.P zones→ γ″-γ′→ γ. This transformation can be achieved by the accumulation of Be-atom layers. The G.P zones are composed of disk-shaped monolayers of Be atoms, which are formed on （001） matrix planes. The intermediate γ″ precipitate is nucleated in the G.P zones. The γ″ and γ′ precipitates have the same orientation relationship with matrix, e.g., （110）p｜｜（100）M,[001]p｜｜[001]M. The tensile strength of specimen shows a maximum during the aging process and then continuously decreases if the specimen is over aged. The strengthening effect of γ′ phase precipitated in aging at 525 ℃ for 4 h is calculated to be 436 MPa according to the Orowan strengthening, which is quite consistent with the experimental data.     

A Novel Cu-10Zn-1.5Ni-0.34Si Alloy with Excellent Mechanical Property Through Precipitation Hardening

A novel Cu-10Zn-1.5Ni-0.34Si alloy was designed to replace the expensive tin-phosphor bronze in this paper. The alloy had better comprehensive mechanical properties than traditional C5191 alloy. The aged Cu-10Zn-1.5Ni-0.34Si alloy had a hardness of 220 HV, electrical conductivity of 28.5% IACS, tensile strength of 650 MPa, yield strength of 575 MPa and elongation of 13%. Ni₂Si precipitates formed during aging, and the crystal orientation relationship between matrix and precipitates was: (001)_α//(001)_δ, and [110]_α//[100]_δ. Ductile fracture surface with deep cavities was found in the alloy. Solid solution strengthening, deformation strengthening and precipitation strengthening were found to be core strengthening mechanisms in the alloy.     

Effects of solution heat treatment on the microstructure, oxidation, and mechanical properties of a cast Ni3Al-based intermetallic alloy

Solution heat treatment is employed in an attempt to improve oxidation and mechanical properties of an as-cast Ni₃Al alloy (IC221M) at operation temperature, 900 °C. Solution heat treatment was hypothesized to have beneficial effects through dissolving γ Ni₅Zr eutectic into the matrix. The microstructures, oxidation behavior in air at 900 °C, and mechanical properties with aging times at 900 °C were examined after solution heat treatment of as-cast Ni₃Al alloy in Ar for up to 100 h at 1100 °C. The oxide penetration depth into the matrix was dramatically decreased and more homogeneous surface oxides were obtained relative to the no solution, treatment case. Hardness was improved by solution heat treatment due to a solid solution strengthening effect by Zr, but the tensile properties after solution heat treatment were not significantly different from those prior to treatment.     

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.     

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.     

Microstructure and mechanical properties of the TiZrNbMoTa refractory high-entropy alloy produced by mechanical alloying and spark plasma sintering

The equiatomic refractory high entropy alloy (HEA) TiZrNbMoTa was investigated. The alloyed powders with face-centered cubic (FCC) structured solid solution phase were prepared by mechanical alloying (MA) and then sintered by spark plasma sintering (SPS) at 1300, 1400, 1500, and 1600 °C. The microstructure and mechanical properties of the bulk alloy were investigated. The body-centered cubic (BCC) structured solid solution phase and the ZrO₂ phase precipitated from the FCC structured solid solution phase during cool-down from sintering. The highest compression fracture strength (3759 MPa) and fracture strain (12.1%) were obtained in the refractory HEA sintered at 1400 °C. The grain boundary strengthening, precipitation strengthening, solid solution strengthening, transformation-induced plastic (TRIP) effect, and toughening effect of the ZrO₂ phase are the important factors for the high strength and ducitily of the refractory HEA prepared in this study.     

Effect of elevated-temperature annealing on microstructureand properties of Cu−0.15Zr alloy

Cu−0.15Zr (wt.%) alloy with uniform and fine microstructure was fabricated by rapid solidification followed by hot forging. Evolution of microstructure, mechanical properties and electrical conductivity of the alloy during elevated-temperature annealing were investigated. The alloy exhibits good thermal stability, and its strength decreases slightly even after annealing at 700 °C for 2 h. The nano-sized Cu₅Zr precipitates show significant pinning effect on dislocation moving, which is the main reason for the high strength of the alloy. Additionally, the large-size Cu₅Zr precipitates play a major role in retarding grain growth by pinning the grain boundaries during annealing. After annealing at 700 °C for 2 h, the electrical conductivity of samples reaches the peak value of 88% (IACS), which is attributed to the decrease of vacancy defects, dislocations, grain boundaries and Zr solutes.     

热机械加工对2099铝锂合金挤压材组织与抗腐蚀性能的影响

采用金相组织观察、XRD分析、硬度和导电率测试等手段,研究了热机械加工(Thermo-Mechanical Processing, TMP)对2099铝锂合金挤压材组织、硬度、导电率、晶间腐蚀及剥落腐蚀性能的影响。结果表明：与经T83 (540 ℃/2 h固溶、3%预压缩、121 ℃/14 h + 181 ℃/48 h时效)热处理的2099铝锂合金挤压材相比,经TMP(540 ℃/2 h固溶、400 ℃/48 h过时效、约50%大应变变形、540 ℃/2 h再结晶/固溶)+(121 ℃/14 h + 181 ℃/48 h时效)处理的2099铝锂合金挤压材发生了明显的再结晶,硬度（HV）降低(从2006.2 MPa到1865.3 MPa),位错强化亦降低,但导电率和抗晶间腐蚀性能明显提高,同时抗剥落腐蚀性能也有所提高。结果表明,热机械加工是不显著降低2099铝锂合金挤压材硬度,但显著提高其抗晶间腐蚀性能的有效途径     

Microstructure and properties of Cu−2Cr−1Nb alloy fabricated by spark plasma sintering

Cu?2Cr?1Nb alloy was fabricated by spark plasma sintering (SPS) using close coupled argon-atomized alloy powder as the raw material. The optimal SPS parameters obtained using the L₉(3⁴) orthogonal test were 950 °C, 50 MPa and 15 min, and the relative density of the as-sintered alloy was 99.8%. The rapid densification of SPS effectively inhibited the growth of the Cr₂Nb phase, and the atomized powder microstructure was maintained in the grains of the alloy matrix. Uniformly distributed multi-scale Cr₂Nb phases with grain sizes of 0.10?0.40 μm and 20?100 nm and fine grains of alloy matrix with an average size of 3.79 μm were obtained. After heat treatment at 500 °C for 2 h, the room temperature tensile strength, electrical conductivity, and thermal conductivity of the sintered Cu?2Cr?1Nb alloy were 332 MPa, 86.7% (IACS), and 323.1 W/(m·K), respectively, and the high temperature tensile strength (700 °C) was 76 MPa.     

不同处理状态下Cu-2.5Fe-0.03P合金的组织与性能演变

以Cu-2.5Fe-0.03P高强高导铜合金带材为研究对象,测试不同处理状态合金板材的力学性能和电学性能,采用金相和电子显微分析方法研究该合金不同加工热处理状态下的组织与性能演变规律及其时效析出特性.并在此基础上研究微量元素Fe和P在合金中的存在形式和作用机制.结果表明:Cu-2.5Fe-0.03P合金热轧后在线固溶态合金基本上为单相固溶体,合金硬度、强度和电导率较低,塑性较好,但还存在少数未溶的Fe相外,在线固溶效果有待进一步改善;软化退火后的薄带进一步冷轧并时效后,合金成品薄带的显微硬度、抗拉强度、屈服强度、伸长率和电导率分别达到147 HV、456 MPa、271 MPa、10.7%和29.9 S/m;热轧-在线固溶-冷轧-时效态Cu-2.5Fe-0.03P合金中的Fe和P以Fe_3P和Fe相形式存在,合金的高强度来源于形变热处理产生的亚结构强化及Fe_3P和Fe粒子的析出强化.     

热加工工艺对引线框架用C194RE铜合金性能的影响

采用微合金化及热机械处理的方法研制了新型的引线框架用Cu-Fe-Zn-P-Mg-Cr-RE（C194RE）铜合金.优化了该合金板材的热加工工艺,获得了优良的合金性能.采用扫描电镜、透射电镜、拉伸试验及硬度测试等研究了合金在不同加工工艺下的显微组织及性能.结果表明：在其它实验条件一致的情况下,热轧后经在线淬火的合金的各项性能均高于热轧后自然冷却的合金的性能.热轧后经在线淬火的合金的抗拉强度可达560 MPa,伸长率达到8.2%.硬度达175HV,电导率为73%IACS.热轧后经自然冷却的合金经热机械处理后,析出相粒子较大,分布也不均匀;而经在线淬火的合金的析出相粒子细小,尺寸为5～20nm,弥散地分布于基体中,析出强化效果显著,并且合金的电导率也较高.     

热处理对Mg-5Zn-0.63Er合金显微组织及力学性能的影响

通过不同的热处理工艺研究含有准晶Ⅰ相的铸态Mg-5Zn-0.63Er(质量分数,％)合金的显微组织演变.结果表明:合金在480℃固溶10 h后,除有W相颗粒析出外,准晶Ⅰ相几乎全部固溶在基体中.固溶态Mg-5Zn-0.63Er合金在175℃下时效6～10h.合金在峰时效态的抗拉强度约为261MPa、伸长率为10.5％.合金拉伸强度的提高归因于杆状MgZn2相的析出.     

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。     

Effect of heat treatment on microstructure and properties of semi-solid squeeze casting AZ91D

Semi-solid AZ91D magnesium alloy billets were prepared by near-liquidus heat holding. Semi-solid squeeze casting was conducted at 575, 585 and 595 ℃, respectively, with 1 mm·s~(-1) squeeze speed. The semisolid squeeze casting AZ91D samples were heat treated by T4(solution at 415 ℃ for 24 h) and T6(solution at 415 ℃ for 24 h + 220 ℃ for 8 h) processes, respectively. The microstructure and mechanical properties of the alloy in different states were investigated by means of OM, SEM and tensile testing machine. The results show that compared to as-cast alloy, the grain size of the semi-solid squeezed AZ91D decreased significantly, and with the increase of semi-solid squeeze temperature, the grain size of AZ91D increased. The grains of the alloy were refined by T4 treatment, and further refined by T6 treatment. T6 treatment greatly improved the tensile strength, elongation, and hardness, but did not significantly improve yield strength. After 575 ℃ squeeze casting and T6 treatment, the ultimate tensile strength(UTS) reached 285 MPa, the elongation reached 13.36%, and the hardness also reached the maximum(106.8 HV), but the yield strength(YS) was only 180 MPa. During the process of semi-solid squeeze casting and heat treatment, the matrix grain was refined and a large number of precipitated and secondary precipitated phases of Mg_(17)Al_(12) appeared. Both the average size of matrix grain and secondary precipitated phase decreased, while the volume fraction of secondary precipitated phase increased. All these resulted in high tensile strength, elongation and hardness.     

Ni含量对Cu−0.4Be合金时效组织和性能的影响

研究Ni含量(0～2.10％,质量分数)对Cu?0.4Be(质量分数,％)合金常规时效析出相、强度和导电率的影响,并分析影响机理.结果表明:添加Ni元素可促进强化相的析出,显著提高时效强化作用.当Ni含量由0增大到2.10％时,合金时效后的强度呈先增大后减小的变化趋势,在Ni含量为1.50％时达到最大;含1.50％Ni...