Cr对标准阴极铜组织与力学性能的影响

在大气环境下采用普通中频感应电炉熔炼制备了Cu-Cr合金,研究了铬对标准阴极铜组.织与力学性能的影响,Cr的加入量分别为0.30%、0.5 3%、0.76%和0.99%.结果表明,在本实验条件下,Cr可以有效地加入到Cu液中.铸态及固溶时效Cu-Cr合金中只存在α-Cu相与Cr相.铸态时部分Cr溶于基体中,部分Cr以第二相形式存在;固溶时效后基体中可分解析出更多弥散分布的Cr相.Cr元素对纯铜有强化作用,合金的铸态和热处理态试样的拉伸强度及硬度均随Cr元素加入量的增大而增加.固溶时效热处理能有效提高铸态Cu-Cr合金的力学性能.     

熔体保温时间对含硅蒙乃尔合金组织与硬度的影响

在真空条件下制备了含硅蒙乃尔合金,采用OM、SEM、TEM与XRD研究了该合金铸态组织特征以及熔体保温时间对含硅蒙乃尔合金硬度的影响.结果表明:合金铸态组织由树枝状α固溶体基体、弥散分布于基体的次生β相及枝晶间呈网状分布的α+3共晶相组成;随着熔体保温时间延长,合金组织中枝晶尺寸先减小后增大,α+3共晶相先减少后增多;合金硬度随保温时间延长呈现出先升高后降低趋势;熔体保温60 min时,合金组织中枝晶尺寸最为细小,α+β共晶相含量最少,合金的硬度达372 HB的最高值.     

Ni含量对Mg-Gd合金组织的影响

采用光学显微镜(OM)、扫描电镜(SEM)、能谱分析(EDS)以及X射线衍射分析(XRD)等手段,研究了Ni含量对Mg98-xGd2Nix(摩尔分数,下同,x=0,0.5,1.0)合金组织的影响。结果表明,铸态下,不含Ni的Mg98Gd2合金组织由初生树枝状α-Mg和分布在树枝间的少量共晶第二相Mg5Gd相组成;添加0.5%的Ni后,合金中Mg5Gd相消失而出现第二相X-Mg12GdNi相,其面积分数达到27%;Ni含量增加至1%时,合金相组成未发生变化,X相面积分数增至42%。在500℃固溶热处理时,随着固溶时间延长,Mg98Gd2合金中第二相Mg5Gd相逐渐溶入基体,而固溶时间达到20h,含Ni的Mg97.5Gd2Ni0.5和Mg97Gd2Ni1合金中第二相X相未发生明显溶解,且基体α-Mg的二次枝晶臂未见明显长大,表明X相具有优良的热稳定性并能有效抑制基体α-Mg的长大。     

Mg-6Al-5Zn-xCa(x=4,5,6,7)-5Gd合金的显微组织和力学性能

研究了不同高含Ca量的Mg-6Al-5Zn-x Ca(x=4,5,6,7)-5Gd合金铸态以及热处理后的显微组织和力学性能。结果表明,铸态时,随着含Ca量的增加,连续分布于晶界处的第二相β-Mg_(25)(Al,Zn)_(37.5)逐渐变细,呈颗粒状的Al_2Gd相和块状的CaZn_5相部分溶解,以更加圆润的小颗粒状相和小块状相分布在组织中,其抗拉强度和屈服强度先升高后降低,伸长率下降;固溶处理后,大部分β-Mg_(25)(Al,Zn)_(37.5)相逐渐溶入合金基体中,合金的强度和伸长率均显著增加,随着含Ca量的增加,固溶组织中分布更多的颗粒状相和块状相,其抗拉强度和屈服强度先升高后降低,伸长率变化不大;固溶+时效处理后,产生时效强化,时效12 h后合金硬度达到峰值,随时效时间延长,硬度稍有降低,然后趋于平缓,说明合金有较优异的热稳定性。断口分析表明,随着含Ca量的增加和热处理方式的不同,合金的断裂机制有从脆性断裂向韧性断裂转变的趋势。当含Ca质量分数为6%时,合金铸态断口形貌中有明显韧窝存在,热处理后,其断口形貌中韧窝数量增多,大小一致,分布趋于均匀。实验合金以Mg-6Al-5Zn-6Ca-5Gd合金经390℃/8 h固溶+200℃/12 h时效处理后的力学性能最佳。     

热处理对Mg_(96.32)Er_2Zn_(1.5)Zr_(0.18)合金组织的影响

采用感应加热制备了Mg96.32Er2Zn1.5Zr0.18合金,对合金进行热处理,利用光学显微镜、扫描电镜背散射电子技术、能谱分析仪以及X射线衍射仪研究了合金不同状态的显微组织。结果表明:铸态Mg96.32Er2Zn1.5Zr0.18合金呈现树枝晶结构,相组成主要为α-Mg相、X相和W相;经过热处理后,合金的树枝晶组织得到完全消除,X相逐渐溶入基体中,合金晶粒尺寸没有发生明显的改变;热处理工艺为530℃×8 h时,合金的X相完全溶入基体中,W相的形态发生变化,由网状转变成谷粒状,同时热处理过程中还析出部分细小的谷粒状W相。     

微量钪、锆对Al-Zn-Mg合金铸态组织演变的影响

对复合添加了稀土元素Sc、Zr的Al-Zn-Mg合金采用光学显微镜(OM)、电子探针(EPMA)、差热分析(DSC)等分析和测试方法,探究不同含量的Sc、Zr添加量对Al-Zn-Mg合金铸态组织演变的影响。结果表明,稀土元素Sc、Zr的复合添加对铸态晶粒产生了细化效果,铸态合金元素大多数偏聚在晶界或者晶内,随着Sc、Zr的含量增加,元素分布趋于均匀,第二相数目开始减少,晶粒大小也逐渐减少。470℃×24 h均匀化退火之后,枝晶组织得到消除,大部分非平衡T相也溶入基体,只有少量难溶的Fe、Si杂质相残留在晶界上,同时合金中重新析出小尺寸的MgZn_2相。随着Sc、Zr含量的增加,第二相的回溶和晶粒细化效果得到了提高。     

工艺参数对Al-Ti-B中间合金第二相粒子的影响

研究了静置时间和加料顺序对铸态Al-Ti-B中间合金第二相粒子形成规律的影响。试验结果表明,随着静置时间的延长,TiAl3的尺寸逐渐增大,在铝基体中的分布更为均匀,且粒子的大小更趋于一致。3种不同的加料顺序中,先加KBF4后加K2TiF6,中间合金中的TiAl3尺寸最大,而混合加盐时TiAl3尺寸最小。TiB2粒子主要分布α-Al边界处,少量分布在TiAl3表面上,静置时间对TiB2粒子分布无影响。     

不同处理态Al-Mg-Si铝合金的组织性能

采用扫描电镜、透射电镜、能谱分析和拉伸测试等手段,研究了热处理对Y、Zr微合金化Al-Mg-Si铝合金显微组织和力学性能的影响。结果表明:添加Y、Zr有助于细化合金铸态晶粒,合金铸态组织在晶界处有明显的偏析,经535 ℃×14 h均匀化处理后偏析现象得到改善。合金经热挤压后,沿挤压方向分布着大量的第二相,随着固溶温度的增加,第二相逐渐溶解在铝基体中。时效处理后,合金中弥散分布着大量的β″相以及其他细小的析出相,起到第二相强化的作用。合金经530 ℃×2 h固溶+180 ℃×8 h时效热处理后的力学性能最佳,抗拉强度达408 MPa,伸长率为14.8%。     

热处理对Mg-5Gd-3Y-0.5Zr合金组织和性能的影响

利用XRD、OM、SEM、EDS、TEM和拉伸性能测试,研究了不同热处理对Mg-5Gd-3Y-0.5Z合金组织和力学性能的影响。结果表明:Mg-5Gd-3Y-0.5Zr合金的铸态组织主要由基体相α-Mg、Mg5Gd和Mg24Y5相组成;经固溶处理后,铸态组织中粗大的析出相基本都溶入α-Mg基体;再经时效处理后,有纳米级别的颗粒状或片状相重新析出。室温条件下,Mg-5Gd-3Y-0.5Zr合金的抗拉强度在T6态达到最大值206.6 MPa。铸态和T6态合金的抗拉强度均随温度的升高,呈现出降低趋势,且下降速度较快;而T4态合金的强度在250℃以前基本保持不变。     

热处理对Mg-2.6Nd-0.6Zn-0.5Zr合金微观组织及晶粒度的影响

采用正交试验法研究了不同热处理对Mg-2.6Nd-0.6Zn-0.5Zr合金微观组织及晶粒度的影响。结果表明:铸态合金主要由镁基体和网状第二相Mg_(12)Nd构成,热处理后合金的晶粒明显长大,由铸态的不规则形状转变为较规则的多边形。通过正交试验法的极差分析得到:随着固溶时间的增加,晶粒尺寸不断增大;随着时效温度或时效时间的增加,晶粒尺寸先减少后增大。热处理参数对晶粒尺寸的影响大小是:固溶时间时效时间时效温度。     

Aging kinetics of 14H-LPSO precipitates in Mg-Zn-Y alloy

Alloys with long-period stacking ordered structures(LPSO)have good properties and are highly regarded.Mg-Zn-Y alloy containing LPSO phase was prepared by the traditional casting method,and the aging heat treatment was performed at different temperatures and times.The microstructure and phase constitutions of the alloy were observed by means of optical microscopy and scanning electron microscopy methods.Results show the microstructure of as-cast Mg95.5Zn1.5Y3 mainly consists ofα-Mg,W phases and LPSO phases.During the aging treatment,fine lamellar-shaped 14H-LPSO phase is formed at the grain boundaries and precipitates from the supersaturated magnesium matrix,and the volume fraction increases as the aging time increases.By controlling the aging time,Mg-Zn-Y alloys with different volume fractions of 14H-LPSO phase were prepared.The aging kinetics equation of the 14H-LPSO phase is summarized,that is f=1-exp(-0.2705 t 0.6368).The phase transformation mechanism of 14H-LPSO in Mg95.5Zn1.5Y3 alloy can be described as the change of dislocation energy.     

细晶TiAl基铸造合金的制备及其凝固特征

采用非自耗电弧熔炼铸造方法,制各了Ti-Al-Nb基铸造合金.通过X射线衍射、金相观察、扫描电镜及透射电镜等实验方法,研究了Al含量对基体合金显微组织与凝固特征的影响.结果表明,适当降低铸造合金中铝的含量,能制备出晶粒细小的Ti-44Al-2Nb-1Cr-1W-1B合金,其平均晶粒尺寸为50 μm.细晶TiAl基铸态合金中β相与γ相存在"伴生"现象;同时,该合金中一定量β相稳定元素W和Nb的加入,使高温β相得以在凝固过程中保留到室温,这种少量β相的存在也限制了a相晶粒的长大.     

热过程对IC21单晶合金组织和力学性能的影响

利用光学显微镜和扫描电镜对IC21单晶合金的铸态、热处理后和不同热过程后的组织进行了观察,检测了铸态、热处理态和不同热过程后合金的高温拉伸和持久性能,研究了热处理和热过程对IC21合金组织演变和力学性能的影响。结果表明,IC21合金的铸态组织呈树枝晶状,由γ′相、γ相以及枝晶间的粗大γ′相和NiMo相组成,枝晶干上γ′相尺寸比枝晶间的γ′相尺寸大。1315 ℃/6 h/充氩冷却+两次时效热处理后合金未实现完全固溶,枝晶干上部分铸态γ′相在固溶时未完全溶解,枝晶间仍存在粗大γ′相,持久性能与铸态相比有明显提升。热过程后,γ′相明显长大,立方度略有降低,枝晶间和枝晶干的γ′相尺寸差距减小,并且有针状相析出。合金的持久寿命与热处理态相比,稍有降低,抗拉强度有所提高。     

Effects of Zr additions on structure and tensile properties of an Al-4.5Cu-0.3Mg-0.05Ti (wt.%) alloy

The effects of different Zr additions(0.05wt.%-0.5wt.%)on the structure and tensile properties of an Al-4.5Cu-0.3Mg-0.05Ti(wt.%)alloy solidified under a high cooling rate(18℃·s^-1),in as-cast and T6 heat-treated conditions were studied.The as-cast structure of the alloy consists of equiaxed grains ofα-Al with an average size of 64μm which is unaffected by the Zr additions,indicating the ineffectiveness of Zr in the grain refinement of the alloy.Scanning electron microscopy,along with X-ray diffraction analysis revealed the presence of elongatedθ-Al2Cu at the grain boundaries;in addition,coarse Al3Zr particles exist in the intergranular regions of the 0.5wt.%Zr-containing alloy.After the T6 heat treatment,the elongatedθparticles were fragmented;however,the coarse Al3Zr particles remained unchanged in the microstructure.Also,the formation of fineβ’-Al3Zr andθ’’-Al3Cu/θ’-Al2Cu phases during T6 heat treatment was revealed by transmission electron microscopy.The results of the tensile tests showed that the Zr additions increase the strength of the alloy in both as-cast and T6 heat-treated conditions,but reduce its elongation,especially with 0.5wt.%Zr addition.The 0.3wt.%Zr-added alloy in the T6 heat-treated condition has the highest quality index value(249 MPa).Fractography of the fracture surfaces of the alloys revealed ductile fracture mode including dimples and cracked intermetallic phases in both conditions.     

Icosahedral quasicrystalline phase in an as-cast Mg-Zn-Er alloy

The microstructure of an as-cast Mg-Zn-Er alloy was investigated through scanning electron microscopy (SEM) and transmission electron microscopy (TEM) equipped with energy dispersive spectroscopy (EDS). The results indicate that two different second phases, one with eutectoid-lamellar morphology and the other with granular shape, distribute in the α-Mg matrix. The coexistence of the face-centered icosahedral quasicrystalline phase (I-phase) and W-phase with the face-centered cubic structure is found in the as-cast alloy. The coexistence of I-phase and W-phasc in the Mg-Zn-Er alloy is because the W-phase is the primary phase and the I-phase forms by peritectic reaction during solidification.     

Analysis of phase in Cu–15%Cr–0.24%Zr alloy

The vacuum medium-frequency induction melting technology was employed to prepare the Cu–15%Cr–0.24%Zr alloy. The scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) were used to analyze the phase composition, morphology and structure of the alloy. The results reveal that the as-cast structure of the alloy consists of Cu matrix, Cr dendrite, eutectic Cr and Zr-rich phase. A large number of Cr-precipitated phases occur in the Cu matrix, and Cu₅Zr particles can be found in the grain boundary of Cu matrix. The HRTEM images prove that there is a semi-coherent relationship between Cu₅Zr and Cu matrix.     

As-cast microstructure of Al-Zn-Mg and Al-Zn-Mg-Cu alloys added erbium

1 INTRODUCTIONMany researches show that the properties ofaluminum and its alloys can be remarkablyi mproved withreasonable rare earth additions .Theactions of rare earth elements in the aluminumalloys consist in alterant-agent , micro-alloying andso on[1 3].By far element scandiumis the most ef-fective rare earth element which i mproves thealuminum alloys properties[4 6]. However , theprice of scandiumis very high.Therefore ,it s veryessential to find a new rare earth element , whichacts …     

Mg-4Zn-1Mn镁合金均匀化热处理及导热率

采用光学显微镜、X射线衍射、布氏硬度测试、扫描电镜、能谱分析等方法,研究新型Mg-4Zn-1Mn(ZM41)镁合金在铸态和不同热处理状态下的显微组织、成分、硬度变化规律。用激光闪射法测定其不同状态的热扩散系数,计算得到导热率值。以空位扩散机制为基础,研究均匀化扩散动力学过程,建立此合金的均匀化扩散方程。结果表明:铸态组织枝晶偏析严重,晶界上有许多粗大的Mg7Zn3非平衡结晶相,Mn以单质形式存在于合金中。经370℃×12 h均匀化热处理后,大部分的Mg7Zn3相已溶入基体。根据实验结果和均匀化动力学计算,确定最佳均匀化处理工艺为370℃×12 h。该合金室温导热率值为125.5 W/(m.K),比常见的镁合金如AZ系、AM系、AS系等的导热性能高出1倍左右。     

Effect of Cu addition on microstructure and properties of Mg-10Zn-5Al-0.1Sb high zinc magnesium alloy

To improve the strength,hardness and heat resistance of Mg-Zn based alloys,the effects of Cu addition on the as-cast microstructure and mechanical properties of Mg-10Zn-5Al-0.1Sb high zinc magnesium alloy were investigated by means of Brinell hardness measurement,scanning electron microscopy (SEM),energy dispersive spectroscopy (EDS),XRD and tensile tests at room and elevated temperatures.The results show that the microstructure of as-cast Mg-10Zn-5Al-0.1Sb alloy is composed of α-Mg,t-Mg32(Al,Zn)49,φ-Al2Mg5Zn2 and Mg3Sb2 phases.The morphologies of these phases in the Cu-containing alloys change from semi-continuous long strip to black herringbone as well as particle-like shapes with increasing Cu content.When the addition of Cu is over 1.0wt.%,the formation of a new thermally-stable Mg2Cu phase can be observed.The Brinell hardness,room temperature and elevated temperature strengths firstly increase and then decrease as the Cu content increases.Among the Cu-containing alloys,the alloy with the addition of 2.0wt.% Cu exhibits the optimum mechanical properties.Its hardness and strengths at room and elevated temperatures are 79.35 HB,190MPa and 160MPa,which are increased by 9.65%,21.1% and 14.3%,respectively compared with those of the Cu-free one.After T6 heat treatment,the strengths at room and elevated temperatures are improved by 20% and 10%,respectively compared with those of the as-cast alloy.This research results provide a new way for strengthening of magnesium alloys at room and elevated temperatures,and a method of producing thermally-stable Mg-10Zn-5Al based high zinc magnesium alloys.     

5059铝合金均匀化金属间相的演变

利用光学显微镜（OM）、扫描电子显微镜（SEM）、透射电镜（TEM）、能谱分析（EDS）、差示扫描量热法（DSC）、X射线衍射（XRD）等手段研究了5059铝合金均匀化热处理过程中金属间相的演变。结果表明：5059铝合金铸锭中枝晶偏析严重,大量难溶金属间相在晶界处呈连续网状分布。难溶金属间相由富含 Zn、Cu 元素的非平衡β（Al3Mg2）相、Fe元素富集的Al6Mn共晶相以及Mg2Si平衡相组成。在均匀化热处理过程中,难溶金属间相发生回溶,并析出大量弥散的β（Al3Mg2）相和短棒状的Al6Mn粒子。根据实验观测及均匀化动力学方程计算结果,得到合金的最佳均匀化热处理制度为（450°C,24 h）。