含银Al-4.5Zn-1.0Mg-0.5Cu合金的强化固溶行为

采用拉伸力学性能测试、金相显微观察、扫描电镜及透射电镜等分析手段,研究了Al-4.5Zn-1.0Mg-0.5Cu-0.4Ag合金的强化固溶行为。结果表明:经强化固溶处理后,合金固溶态的抗拉强度和屈服强度以及伸长率分别较常规固溶的低15 MPa、16 MPa和1.7%;峰值时效态的抗拉强度和屈服强度较常规固溶的分别高62 MPa和68 MPa,伸长率低0.8%。;强化固溶可使Al-4.5Zn-1.0Mg-0.5Cu-0.4Ag合金固溶后的第二相粒子减少,但使其时效后的强化相数量增多,密度增大。     

固溶时效处理对Al-6.6Zn-2.3Mg-2.1Cu-0.12Zr合金组织性能的影响

采用光学显微镜、扫描电镜、透射电镜、X射线衍射、硬度测试、电导率测试和室温拉伸性能测试等分析手段,研究了Al-6.6Zn-2.3Mg-2.1Cu-0.12Zr合金挤压板带固溶、单级时效和双级时效制度下的组织和性能。研究表明,Al-6.6Zn-2.3Mg-2.1Cu-0.12Zr合金挤压板带采用475℃/2 h的固溶处理制度,析出相回溶充分,无过烧现象;合金采用475℃/2 h+120℃/24 h的T6时效处理制度,晶内析出相细小弥散,晶界析出相连续分布;合金采用475℃/2 h+110℃/8 h+160℃/28 h的T74双级固溶时效处理制度,晶内析出相以η’和η为主,晶界析出物完全断开。     

含锶钪2099型铝锂合金的晶间腐蚀和剥落腐蚀性能

采用维氏硬度计(HV)、金相显微镜(OM)和扫描电镜(SEM)显微分析技术,研究了一种锶钪复合微合金化2099型铝锂合金(其化学成分为:Al-2.57Cu-1.86Li-1.31Zn-0.420Mg-0.321Mn-0.0735Zr-0.0943Sr-0.0433Sc)的晶间腐蚀性能和剥落腐蚀性能。结果表明,该合金经均匀化退火处理(475℃×24 h)、热锻压变形加工处理(三次变形量均约为100%)、固溶处理(540℃×2 h)、冷水淬火(水温大约5℃)、T8时效处理(121℃×14 h+151℃×48 h)后,合金显微硬度值达到174.6 HV,比2024-T6合金(固溶处理500℃×2 h+时效处理191℃×12 h)高23.1%。合金具有良好的抗晶间腐蚀性能和抗剥落腐蚀性能,其抗腐蚀性能明显优于2024-T6合金。该合金Sr,Zr,Sc的复合微合金化作用(细化粗大第二相、抑制再结晶和晶粒长大),第二相分散、分布不连续,以及Zn的含量高,是合金抗腐蚀性能高的主要原因。研究结果还说明了微量复合添加对铝锂合金具有奇效微合金化作用的过渡族金属元素Sr,Sc,是得到抗腐蚀性能良好的铝锂合金的一种有效途径。     

Microstructure and properties of as-cast Cu-Cr-Zr alloys with lanthanum addition

Cu-0.45Cr-0.2Zr-xLa (x = 0–0.48) alloys were prepared by vacuum casting. The effects of La addition and orientation on the microstructure and properties of the as-cast alloy were investigated by an optical microscope, a scanning electron microscope with an energy dispersive X-ray spectrometer, a tensile testing machine and an electrical conductivity tester. The result shows that the addition of La significantly refines the columnar grainsize and decreases the secondary dendrite arm spacing. Trace addition of La improves the room temperature ultimate tensile strength, elongation and electrical conductivity mainly by purifying during melting and casting. The ultimate tensile strength, elongation and electrical conductivity significantly decrease with the increase of La content due to formation of coarse particles and oxides, which severely harm the performance of the Cu-0.45Cr-0.2Zr-xLa alloys. The Cu-0.45Cr-0.2Zr-0.13La alloy possesses a good combination of room temperature ultimate tensile strength, elongation and electrical conductivity. In addition, room temperature ultimate tensile strength and electrical conductivity along transverse direction of the ingot are higher than that along longitudinal direction, which is mainly ascribed to different distribution of grain boundary and grain orientation.     

轻质Al-Mg-Li合金的微观组织与力学性能

采用熔炼和热挤压制备轻质Al-5.5Mg-2.0Li-0.1Zr-0.2Sc合金,利用X射线衍射仪、差示扫描量热仪、金相显微镜、扫描电子显微镜、显微硬度计及拉伸试验机对合金的物相组成、微观组织、力学性能及断口形貌进行检测分析,研究时效工艺温度（120 ℃和160 ℃）对合金微观组织和力学性能的影响.结果表明:Al-Mg-Li合金挤压后晶粒组织呈纤维状,存在一定数量的Al₃Li（δ′）和Al₂MgLi（S）相;经固溶和时效处理后,再结晶晶粒尺寸变大,主要析出相为δ′相S相;160 ℃时效处理容易加速时效析出行为,导致析出相粗化,强化效果减弱;经120 ℃/20 h峰时效处理后,合金的抗拉强度、屈服强度和延伸率分别达到532 MPa、475 MPa和4.4 %.      

Al-2.3Cu-1.7Mg-1.2Fe-1.2Ni合金的时效行为研究

采用硬度测试、电导率测试、常温力学性能测试等方法研究了单级时效处理过程中时效温度和时效时间对Al-2.3Cu-1.7Mg-1.2Fe-1.2Ni合金力学性能和电导率的影响规律,并利用金相显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)、选区电子衍射(SAED)等手段对合金淬火态以及几种不同时效处理制度下的显微组织进行了研究.结果表明,合金经固溶淬火处理后仍残留有较多的大尺寸第二相,淬火态组织存在的第二相主要有Al9FeNi,Al7 Cu2 Fe,Al7 Cu4 Ni等.单级时效处理过程中,时效处理的温度越高,达到峰时效所需的时间越短,材料的峰时效硬度值越低;电导率随时效时间的延长而不断上升,时效温度越高,电导率的增长速率越快.峰时效条件下合金内主要沉淀强化相包括S’相和S"相,晶界上有明显的链状析出物存在,呈不连续分布;峰时效条件下,合金棒材的极限抗拉强度、屈服强度和延伸率分别为455 MPa,391 MPa和10.6％,电导率可达到21.6 MS·m-1.     

Influence of Nd and Y additions on the corrosion behaviour of extruded Mg-Zn-Zr alloys

To improve the corrosion resistance of wrought magnesium alloys through rare earth (RE) additions, the corrosion behaviour of Mg-5Zn-0.3Zr-xNd (x=0, 1, and 2; wt%) and Mg-5Zn-0.3Zr-2Nd-yY (y=0.5 and 1; wt%) alloys in a 5wt% NaCl solution was investigated using immersion test and electrochemical measurements. The results of immersion test show that Mg-5Zn-0.3Zr-2Nd alloy exhibits the best corrosion resistance among the tested alloys. Electrochemical measurements show that secondary phases in RE-containing Mg-5Zn-0.3Zr alloys behave as less noble cathodes in micro-galvanic corrosion and suppress the cathodic process. The additions of Nd and Y into Mg-5Zn-0.3Zr alloy also improve the compactness of the corrosion product film and are beneficial to the corrosion resistance.     

Microstructure and mechanical behavior of spray-deposited High-Li Al-Li alloys

High-Li alloys, with the composition Al-3.8Li-XCu-1.0Mg-0.4Ge-0.2Zr, were synthesized using a spray deposition technique (wt. pct, X=0∼1.5). The microstructure of the spray-deposited Al-Li alloys consisted of equiaxed grains with an average grain size in the range from 20 to 50 μm. The grain-boundary phases were fine and discrete. The spray-deposited and thermomechanically processed materials were isothermally heat treated at 150 °C and 170 °C to investigate the age-hardening kinetics. It was noted that the spray-deposited Al-3.8Li-XCu-1.0Mg-0.4Ge-0.2Zr alloys exhibited relatively sluggish aging behavior. The peak-aged condition was achieved at 170 °C in the range from 20 to 90 hours. It was noted that Cu increases the hardness of alloys during aging. Moreover, the influence of Cu on age-hardening kinetics is marginal. The mechanical properties of the spray-deposited and extruded Al-Li alloys were studied in the underaged, peak-aged, and overaged conditions. For example, the peak-aged yield strength, tensile strength, and ductility of Al-3.8Li-1.0Cu-1.0Mg-0.4Ge-0.2Zr are 455 MPa, 601 MPa, and 3.1 pct, respectively. Moreover, an increase in the Cu content of the alloy led to improvements in strength, with only slight changes in ductility, for Cu contents up to 1.0 wt pct. Beyond this range, an increase in Cu content led to decreases in both strength and ductility.     

Al-4.9Zn-1.6Mg-0.4Mn-0.1Zr-xEr合金时效行为研究

采用金相(OM)、透射电镜(TEM)及能谱分析(EDS)、硬度测试的方法研究了单级与双级时效热处理制度对Al-4.9Zn-1.6Mg-0.4Mn-0.1Zr-xEr合金板材硬度和显微组织的影响.结果表明,添加Er元素后合金中形成了纳米级的A13(Zr,Er)相,可以强烈地钉扎位错,细化再结晶晶粒.无论单级时效还是双级时效,Er元素的添加均可以提高合金的硬度,加快合金的时效硬化速率,使合金达到硬度峰值的时间缩短,但Er含量对提高合金硬度的影响不大.同时,晶界处出现的第二相颗粒析出带得到消除,合金中存在明显的沉淀无析出带.此外,Er元素可以促进Zn,Mg元素的固溶,而析出的A13(Zr,Er)颗粒又可以促进MgZn2相的析出.     

稀土元素Sm对Mg-Zn-Y合金组织结构和力学性能的影响

制备了Mg-6Zn-1.5Y-0.8Zr-xSm(x=0,1,2,3)系列合金,研究了稀土元素Sm对Mg-6Zn-1.5Y-0.8Zr合金组织结构和力学性能的影响.通过金相显微镜、扫描电镜、EDS、XRD等观察和分析了合金的微观形貌和组织结构,测量了合金抗拉强度、屈服强度和伸长率等力学性能.结果表明:合金中添加稀土元素Sm后晶粒有了明显的细化,随着Sm元素含量的增加,晶粒细化效果更为明显;通过XRD分析,添加Sm元素后,合金中并没有出现新的含Sm的物相,通过扫描电镜和EDS分析表明,合金中加入的Sm置换了部分Y,形成了Mg3( SmY)2 Zn3,Mg3( SmY) Zn6的相结构,Sm元素对Y的置换主要出现在Mg3( SmY) Zn6结构当中,在Mg3 (SmY) Zn6相结构出现较少;力学性能测试结果表明,随着Sm含量增多,合金晶粒细化,细晶强化作用明显,合金屈服强度逐渐增大,而抗拉强度和伸长率在Sm含量为2％时达到最大,比未添加Sm元素时提高约15％以上.     

Quantification of overaging hardening kinetics of aluminum alloys

The overaging hardening kinetics in several aluminum alloys has been quantified, based on a relation between hardness and time for precipitation-hardened alloys. The relation takes into account precipitate coarsening and Orowan bowing mechanisms. Hardness-time curves from literature data for Al-2.5Cu-1.5Mg-(Si,Ag) (wt pct) alloys at 200° C and for an Al-1.23Mg-1.64Cu-6.15Zn (wt pct) alloy at 120° C are analysed, which are found to obey the overaging kinetics relation.     

Effect of phosphorus modification on the microstructure and mechanical properties of DC cast Al-17.5Si-4.5Cu-1Zn-0.7Mg-0.5Ni alloy

Direct chill (DC) casting of an Al-17.5Si-4.5Cu-1Zn-0.7Mg-0.5Ni alloy with minor additions of Zr, V and Ti was performed and the effect of phosphorus modification on the solidification microstructure and mechanical properties were investigated. The results show that the addition of phosphorus refines the primary Si crystals remarkably but coarsens the eutectic Si in the DC cast billets. In the samples taken in 1/2 radius region of the billets of 100 mm in diameter, the average size of the primary Si particles in the unmodified alloy is 38 μm, while that in the modified alloys range from 13 to 26 μm, depending on the melt treatment time. The AlP particles as heterogeneous nucleation sites for the primary Si crystals were observed in the center of the primary Si particles. In the modified alloy, the achieved ultimate tensile strength is 320MPa and 433MPa respectively in the as-cast state and T6 state. The size of the primary Si particles is critical for the improvement of the mechanical properties of the alloy.     

微量元素对Al-1.2Mg-1.3Si-0.6Cu-0.3Mn铝合金组织性能的影响

The effects of impurity element of Fe and microelements of Zn, Cr and Ti on the constituents,dispersoids, grain size, mechanical properties and formability of Al-1.3Mg-1.2Si-0. 6Cu-0. 3Mn alloy were investigated in the present work by analyzing microstructures, phase composition, mechanical tests. The resuits indicated that with the increase of Fe content, the insoluble constituents increased, and the mechanical properties and r15 of alloy sheets debased, which can be recovered by the addition of microelements Zn, Cr and Ti. Al-1.3Mg-1.2Si-0. 6Cu-0. 3Mn alloy sheets in the T4 temper are difficult to strengthen with paint -bake treatment in automobile factory.     

Effect of zinc and mischmetal on microstructure and mechanical properties of Mg-Al-Mn alloy

Mg-2Al-0.5Mn alloys with 0-0.5% Zn and 0.5%-1.0% La-Ce misch metal (MM) were prepared by metal mould casting method. Effect of alloying elements Zn and MM on microstructures were investigated by X-ray diffraction, optical microstructure and scanning electron microscope. The results showed that Zn and MM additions led to an obvious grain refinement. Addition of 0.5% Zn resulted in about 30% reduction in grain size for Mg-2Al-0.5Mn alloys, while 0.5% MM addition caused about 40% reduction in grain size. The t...     

Effect of Natural Aging and Cold Working on Microstructures and Mechanical Properties of Al-4.6Cu-0.5Mg-0.5Ag alloy

This research investigates the effects of natural aging and cold working prior to artificial aging on microstructures and mechanical properties of Al-4.6Cu-0.5Mg-0.5Ag alloy. Mechanical properties relative to microstructure variations were elucidated by the observations of the optical microscope (OM), differential scanning calorimeter (DSC), electrical conductivity meter (pct IACS), and transmission electron microscopy (TEM). The results showed that natural aging treatment has little noticeable benefit on the quantity of precipitation strengthening phases and mechanical properties, but it increases the precipitation strengthening rate at the initial stage of artificial aging. Cold working brings more lattice defects which suppress Al-Cu (GP zone) and Mg-Ag clustering, and therefore the precipitation of Ω phase decreases. Furthermore, more dislocations are formed, leading to precipitate the more heterogeneous nucleation of θ′ phase. The above-mentioned precipitation phenomena and strain hardening effect are more obvious with higher degrees of cold working.     

Nd对Mg-11Li-3Al-2Zn-0.2Zr合金组织、力学性能及腐蚀行为的影响

研究稀土Nd对均匀化态Mg-11Li-3Al-2Zn-0.2Zr合金组织、力学性能及腐蚀行为的影响.通过真空感应熔炼制备镁锂合金铸锭, 经均匀化处理(280 ℃, 24 h)得到均匀化态Mg-11Li-3Al-2Zn-xNd-0.2Zr(x=0, 0.5, 1.0, 1.5)合金.采用XRD和SEM分析合金的显微组织, 并对合金进行拉伸试验和断口分析.采用电化学法和析氢失重法研究合金在3.5 %NaCl溶液中的腐蚀行为.结果表明:Mg-11Li-3Al-2Zn-0.2Zr合金主要含有β-Li、AlLi、MgLi₂Al相, Nd的加入使合金中形成NdAl3相.随着Nd含量的增加, 合金的强度和塑性呈先增大后降低的趋势. Mg-11Li-3Al-2Zn-1Nd-0.2Zr合金表现出较优的力学性能, 其抗拉强度和延伸率相对于Mg-11Li-3Al-2Zn-0.2Zr合金分别提高了28.8 %和51.3 %.稀土Nd的添加使合金的耐蚀性能提高.      

时效工艺对Al-11Zn-2.4Mg-1.1Cu-0.15Zr铝合金性能的影响

Al-11Zn-2.4Mg-1.1Cu-0.15Zr铝合金自然时效的速度慢,且不稳定,故一般不在自然时效状态下应用.为了获得更高的强度、较好的抗蚀性、较低的疲劳裂纹扩展速度以及性能的稳定,该系合金一般采用人工时效处理.热处理工艺参数主要包括固溶处理温度、固溶处理时间、时效温度、时效时间.本实验研究了时效工艺对Al-11Zn-2.4Mg-1.1Cu-0.15Zr铝合金性能的影响,旨在摸索Al-11Zn-2.4Mg-1.1Cu-0.15Zr铝合金的合理热处理工艺.     

Influences of different Zr/Sc ratios on microstructure and mechanical properties of Al-2Si alloy

The influences of different Zr/Sc ratios on the microstructural evolution and mechanical performances of Al-2 Si alloy were investigated in this paper.The as-cast samples were characterized and analyzed by the scanning electron microscope(SEM) with an energy dispersive spectrometer(EDS) to indicate the refining effect of the different Zr/Sc ratios on the α-Al and Si phases in Al-2 Si alloy.The results indicate that the α-Al phases are refined from coarse dendritic structure to relatively fine equiaxed grains when the Zr/Sc ratio is equal to 1:1.Meanwhile,the eutectic Si phase in Al-2 Si-0.2 Zr-0.2 Sc alloy is modified from the coarse plate and needle to fine fiber and partial granular structure,and the average roundness of eutectic Si is decreased by 75% from 16 to 4.With the refinement of α-Al phases and the modification of eutectic Si structure,the ultimate tensile strength(UTS) is improved by 53% and the elongation(EL) is increased by 64% when the Zr/Sc ratio is equal to 1:1.In addition,the UTS decreases and EL is enhanced with the increase of tensile temperature.Moreover,the fracture model of Al-2 Si-0.2 Zr-0.2 Sc alloy in250℃ changes into the ductile fracture.     

Al-Sc-Zr master alloy and estimation of its modifying capacity

An Al-1.1 Sc-1.1 Zr (wt %) master alloy with a uniform distribution of micron and submicron particles of aluminide phase Al₃(Sc_{1 − x} Zr _x ) has been obtained by exposing of equal amounts of commercial Al-Sc and Al-Zr master alloys to short-time actions of low-frequency vibrations transferred to the alloy via an irradiating plunger. Zirconium substitutes up to 50% Sc in aluminides and retains its L1₂ lattice. The modifying capacity of the experimental master alloy is tested on cast alloy (wt %) Al-8Zn-2.4Cu-3Mg. Intense grain refinement of this alloy is achieved by its modification with a certain amount of the master alloy. At a certain Sc + Zr content, a grain dendrite structure completely disappears in the alloy.