Effect of rheo-diecast process on the mechanical properties of A390 alloy by serpentine channel

In this paper, the effects of rheo-diecast process parameters and T6 heat treatment on the microstructure and mechanical properties of the rheo-diecasting (RDC) semi-solid A390 alloy prepared through pure copper serpentine channel were investigated. The results indicate that the mechanical properties of the RDC samples change with the pouring temperature and injection pressure. In this case, a lower pouring temperature results in better tensile strength and elongation of the RDC A390 alloy; however, the tensile strength and elongation decrease when the pouring temperature decreases to 660°C. Higher injection pressures result in the improved mechanical properties of the RDC A390 alloy. To some extent, T6 heat treatment improves the tensile strength and ductility of the RDC A390 alloy compared to those of the non-heat treated alloy. However, when the pouring temperature and injection pressure are greater than 670°C and 70 MPa, respectively, the mechanical properties are sharply diminished.     

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.     

电脉冲孕育处理对Al-5%Cu-0.8%Mn合金组织及性能的影响

通过凝固组织观察、力学性能测试、断口分析等实验,研究了不同电脉冲孕育处理对Al-5%Cu-0.8%Mn合金组织和性能的影响.实验结果表明,不同电脉冲处理参数均使Al-5%Cu-0.8%Mn合金凝固组织细化,单位面积晶粒数提高2倍以上;合金力学性能较未处理试样明显改善,抗拉强度增加了21%～35%,伸长率提高1.8～2.5倍;且当脉冲电压500V、时间30s、频率3Hz时,合金的凝固组织细化效果最好,力学性能最佳.     

Structural and mechanical properties of 7075 alloy strips fabricated by roll-casting in a static magnetic field

The influences of a 0.2 T static magnetic field on the microstructure of 7075 aluminum alloys sheets produced with a twin-roll continuous caster at 675°C were investigated in this paper. Under a uniform magnetic field, the primary dendrites were refined and tended to be equiaxed. The microstructure consisted of an intermediate case between dendritic and equiaxed grains. Moreover, the use of an external static field in the twin-roll casting process can reduce heat discharge, resulting in a decrease in undercooling, and may also account for the abatement of segregation bands. In addition, the static magnetic field effectively improved the solute mixing capacity, and the added atoms more easily diffused from precipitates to the α-Al matrix, which resulted in an increase in the mechanical properties of the rolled sheets. Specimens prepared both in the presence of a static magnetic field and in the absence of a static magnetic field exhibited brittle-fracture characteristics.     

AZ31镁合金氩弧焊接接头组织与力学性能研究

钨极氩弧焊(TIG)为镁合金焊接中最常用的一种焊接方法。本文采用直流钨极氩弧焊对6.0 mm厚AZ31镁合金挤压板材进行了双面焊接实验。采用光学显微镜、扫描电镜、拉伸试验机考察分析了焊接接头显微组织与力学性能。显微组织分析表明,AZ31镁合金直流TIG焊接头由母材、热影响区、焊缝区组成,焊缝组织呈现焊丝熔化后凝固组织;在母材热影响区与焊缝区之间坡口处形成过渡区,晶粒细小,为母材与焊丝的熔合区。采用AZ31焊丝焊接接头平均抗拉强度为241.0 MPa,延伸率为13.8%,分别达到了母材的86.0%和63.6%。焊接接头的断裂均位于热影响区,断口呈现韧脆混合断裂特征。     

强化固溶态2024铝合金ECAP加工后的拉伸性能

在室温下对经强化固溶处理的2024铝合金实施了等效应变为0．5的等通道转角挤压（ECAP）,将强化固溶、形变、时效和晶界细化四者有机结合,制备出超高强铝合金,其硬度、屈服强度、伸长率分别高达约191HV,610MPa和13％．强度-结构关系的定量计算表明,ECAP变形过程中所引入的位错,其对强度提升的贡献高达整个强度提高值的62．2％．研究结果还表明,强化固溶→低温ECAP变形→低温人工时效是提升常规铝合金的强度、制取超高强铝合金的一条有效途径。     

Effects of P addition on the microstructure and mechanical properties of Mg–5%Sn–1.25%Si alloy

The effects of Al-P addition on the microstructure and mechanical properties of as-cast Mg–5%Sn–1.25%Si magnesium alloy were investigated. The results show that the phases of the as-cast alloy are composed of α-Mg, Mg2 Sn, Mg2 Si, little P, and AlP. The Chinese character shape Mg2 Si phase changes into a granular morphology by P addition because AlP can act as a heterogeneous nucleation core for the Mg2 Si phase. When 0.225wt% of Al–3.5%P alloy is added, the mechanical properties of the Mg–5%Sn–1.25%Si alloy are greatly improved, and the tensile strength increases from 156 to 191 MPa, an increase of 22.4% compared to the alloy without P addition. When the amount of Al–3.5%P reaches 0.300wt%, a segregation phenomenon occurs in the granular Mg2 Si phase, and the tensile strength and hardness decrease though the elongation increases.     

MgZnCa合金的组织结构和力学性能分析

通过铜模吸铸法制备直径为3mm的Mg-Zn-Ca三元共晶合金,按成分比例配制的合金分别为Mg72Zn15Ca13、Mg62Zn36Ca2、Mg14Zn22Ca64和Mg26Zn48Ca26.利用X射线衍射仪(XRD)、光学显微镜(OM)、微机控制电子式万能试验机和扫描电子显微镜(SEM)对MgZnCa合金的组织结构、力学性能和断口形貌进行研究.结果表明:Mg72Zn15Ca13、Mg14Zn22Ca64和Mg26Zn48Ca26合金形成非晶相和晶体相共存的复合材料,Mg62Zn36Ca2形成纯晶体;其中强度最高、塑性最好的是Mg14Zn22Ca64,其强度和塑性应变分别为548MPa和0.9%;对于该合金系,强度随结晶度降低而升高;压缩断口形貌显示,Mg72Zn15Ca13、Mg62Zn36Ca2、Mg14Zn22Ca64和Mg26Zn48Ca26合金均为脆性断裂.     

双级过时效工艺对7050铝合金力学性能的影响

双级过时效是优化工业化大尺寸7050铝合金锻件综合性能的有效手段。对7050铝合金锻件进行双级过时效处理,研究第二级时效时间对其组织与力学性能的影响。结果表明,随着第二级时效时间的延长,晶界处析出相逐渐粗化,并由连续分布转变为断续分布,合金的硬度、屈服强度和抗拉强度随之降低,伸长率与断裂韧性逐渐升高,并且拉伸及断裂韧性测试样品的断裂模式从沿晶断裂向韧窝型断裂转变。当第二级时效时间延长至一定程度时,合金力学性能趋于平稳。为通过双级过时效工艺调控7050铝合金锻件的综合力学性能提供了研究基础和理论指导。     

升温固溶对Al-Zn-Mg-Cu合金组织与力学性能的影响

研究了7075合金升温固溶处理过程．结果表明升温处理可使极限固溶温度高于多相共晶温度,同时能避免过烧组织的形成,有效强化了残余结晶相的固溶,显著提高了7075合金的力学性能．通过强化固溶,7075合金的断裂和屈服强度可达660MPa和606MPa．     

Microstructure and mechanical properties of ZE10 magnesium alloy prepared by equal channel angular pressing

ZE10 magnesium alloy was subjected to equal-channel angular pressing (ECAP) up to 12 passes in a die with an angle of 120° between the two channels at 250-300℃. An inhomogeneous microstructure of bimodal grains including fine grains of 1-2 μm as well as coarse grains of about 20μm was obtained after the initial 1-4 ECAP passes. The grain size became increasingly homogeneous with further ECAP processing and the grains were significantly refined to 1-2 ktm after 8 passes and further refined to 0.5-1 μm after 12 passes. The alloy's yield strength changed slightly but the ductility improved greatly initially up to 4-6 passes corresponding to the bimodal grain microstructure. And after the subsequent pressing of more than 8 passes, the tensile strength including yield strength improved while the elongation decreased gradually.     

固溶时效工艺对6016铝合金力学性能的影响及多目标优化

作为6XXX铝合金热处理工艺的一部分,固溶处理与时效处理对6016铝合金的力学性能有显著影响.本文把固溶温度、时间和时效温度、时间作为设计变量,应用中心组合实验设计法设计固溶-时效实验方案,在室温下分别测出试样的屈服强度、伸长率和维氏硬度.第二代非支配排序遗传算法(NSGA-Ⅱ)解决了第一代算法参数选取难、运行效率低等缺点.本文用第二代非支配排序遗传算法把得到的响应面方程作为目标函数进行多目标优化,经过计算后获得非劣解,从中可筛选出使目标函数较好的解与相对的固溶-时效工艺参数.     

Microstructural characterization of as-cast and homogenized 2D70 aluminum alloy

The microstructure of the as-cast 2D70 aluminum alloy and its evolution during homogenization were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) analysis. The results indicate that the microstructure of the as-cast 2D70 aluminum alloy mainly consists of the dendritic network of aluminum solid solution and intermetallic compounds (Al₂CuMg, Al₂Cu, Al₉FeNi, Cu₂FeAl₇, and Al₇Cu₄Ni). After conventional homogenization, Al/Al₂CuMg eutectic phases are dissolved into the matrix, and a small amount of high melting-point eutectic Al/Al₂Cu phases exist in the matrix, resulting in an increase in the starting melting temperature. Under double homogenization, the high melting point Al/Al₂Cu phases are dissolved, and no obvious change is observed for the size and morphology of Al₉FeNi, Cu₂FeAl₇, and Al₇CuaNi compounds.     

搅拌摩擦加工IF钢的组织性能

对3 mm厚的DC04冷轧IF钢板进行搅拌摩擦加工,研究加工区域的微观组织与力学性能. 在旋转速度为950 r· min-1 ,加工速度为60 mm·min-1时,采用加工后强制冷却技术可获得光滑平整且没有缺陷的加工表面. 搅拌摩擦加工后组织显著细化,加工中心的平均显微硬度约为HV 135. 6,是母材硬度的1. 4倍,表面细晶层硬度最高可达到HV 312. 8,细晶层和过渡层的抗拉强度分别比母材的抗拉强度提高50. 9%和47. 6%,加工前后试样的拉伸断口均呈微孔聚合韧性断裂特征. 细晶强化对材料抗拉强度的提高起主要作用.     

Solidification,microstructure, and mechanical properties of the as-cast ZRE1 magnesium alloy with different praseodymium contents

The influence of praseodymium (Pr) content on the solidification characteristics, microstructure, and mechanical properties of ZRE1 magnesium (Mg) cast alloy was investigated. The obtained solidification parameters showed that Pr strongly affected the solidification time, leading to refinement of the microstructure of the alloys. When the freezing time was reduced to approximately 52 s, the grain size decreased by 12%. Mg₁₂Zn (Ce,Pr) was formed as a new phase upon the addition of Pr and was detected via X-ray diffraction analysis. The addition of Pr led to a substantial improvement in mechanical properties, which was attributed to the formation of intermetallic compounds; the ultimate tensile strength and yield strength increased by approximately 10% and 13%, respectively. Pr addition also refined the microstructure, and the hardness was recovered. The results herein demonstrate that the mechanical properties of Mg alloys are strongly influenced by their microstructure characteristics, including the grain size, volume fraction, and distribution of intermetallic phases.     

流变压铸工艺参数对半固态A356铝合金充填性的影响

研究了半固态A356铝合金浆料的成形温度、压射比压和压射冲头速度对半固态A356铝合金流变压铸充填性的影响.实验结果表明:较高的半固态A356铝合金浆料的成形温度有利于获得良好的充填性.压射比压和压射冲头速度对半固态A356铝合金浆料充填性也具有较大的影响.在本实验条件下,压射冲头速度越大或压射比压越大,充填性越好.试片的壁厚对半固态A356铝合金浆料的充填性影响较大,试片壁厚越大,越容易充填.此外,采用低过热度浇注和弱电磁搅拌技术制备的A356铝合金浆料和流变压铸试片的组织分布很均匀,有利于获得优质的半固态压铸件.     

TC4钛合金搅拌摩擦焊微观组织特征及影响

采用搅拌摩擦焊技术在保护气氛下对单块TC4钛合金板材施焊,并获得良好成形。重点研究了搅拌区α+β双相微观组织演变机制及不同工艺参数对组织硬度的影响。结果表明,在经优化后的工艺参数条件下,搅拌区组织经历了α/β相变,最终形成基于β相区的α+β双态组织,搅拌头行走过后冷却析出的层片状α相沿β相区界面及内部分布,α相及β相晶粒细化明显,α/β层片间距的缩小可增强α+β复相强化效应,提高搅拌区硬度。搅拌头转速的提高增加了β相区的长大倾向,行进速度的提高降低了α相比例,并可生成针状马氏体。     

Evolution of the texture and mechanical properties of 2060 alloy during bending

In this study, we examined the evolution of the texture and mechanical properties of 2060 (T8) alloy during bending. A pixel rotation method (PRM) was proposed and used to characterize the textural evolution during bending determined by electron backscatter diffraction. The results showed that the textural components changed insignificantly, with the exception of a decrease in the cube texture. The tensile and yielding properties of the alloy were evaluated at three different orientations with respect to the rolling direction. The mechanical strength was found to increase in three directions with decreasing bending radius; thus, it was concluded that the 2060 (T8) alloy sheet satisfies the usage requirement after bending deformation.     

输运理论中原子核初始化研究

基于同位旋相关的量子分子动力学(IQMD)输运理论模型,研究中能重离子碰撞的初始化问题。成功的初始化可以很好地减少碰撞过程中出现的非物理涨落和虚粒子发射,有利于两体碰撞过程顺利进行。计算发现,不同的对称势对原子核的稳定性有一定的影响。选取不同质量数的Fe,Kr,Sn元素及其同位素,通过其在自身平均场中随时间的演化来验证原子核的稳定性,统计出初始化稳定原子核的数量,选取出最为稳定的对称势。发现平方项的对称势U₂最为稳定,其对应的斜率L、不可压缩系数K_sym都在已知的约束范围内,表现出同位旋相关平均场取硬势时,原子核更为稳定的特征。     

混合稀土对Mg-9Y-0.6Zr镁合金组织和性能的影响

通过光学显微镜、X射线衍射仪(XRD)、描扫电镜(SEM)、微分扫描量热仪(DSC)和力学性能测试等手段,研究了加入质量分数为0%、1%、3%和5%混合稀土对Mg-9Y-0.6Zr(WK90)镁合金组织及性能的影响.结果表明:铸态WK90合金组织由α-Mg基体及少量的共晶组织构成,添加混合稀土后,晶界处的共晶组织明显增多,并由单一共晶形式转变为层状共晶和离异共晶并存;随着混合稀土添加量的增大,共晶组织的种类及数量增多,合金DSC曲线的低熔点吸热峰总面积增大并最终发生分离;混合稀土为3%铸态合金及含混合稀土为1%的挤压态合金分别具有最高的断裂强度,影响合金强度的因素除了晶粒尺寸外,离异共晶组织的分布状态和形貌也是重要的因素.