均匀化处理和挤压对Mg-Y-RE-Zr合金组织性能的影响

通过调整元素Y的含量,制备了多种Mg-Y-RE-Zr镁合金,对合金不同状态下微观组织和力学性能进行了分析和测试.结果表明,不同合金晶界上的化合物以Mg24Y5,Mg41Nd5,Mg5Gd等为主,随着元素Y含量的增加,晶界上的化合物数量和尺寸增加,晶粒平均尺寸变化较小,保持在50～60μm;经过均匀化处理(535℃×24 h)后,合金中化合物的分布由铸态时连续的岛状分布变为弥散细小的颗粒状分布,Mg5Gd相基本上全部分解并溶入基体中,合金中弥散分布的点状颗粒相主要为Mg24Y5和Mg41Nd5相;经过挤压变形后,合金的组织得到细化,平均晶粒尺寸在20μm左右,合金的抗拉强度、屈服强度和伸长率都有大幅度的提高,其中Mg-5Gd-5Y-3Nd.0.5Zr合金表现出了较好的综合力学性能;在设计的合金中,元素Y的含量(质量分数)应控制在5%以下.     

Microstructural evolution and mechanical properties of Mg-5Y-5Gd-<Emphasis Type="Italic">x</Emphasis>Nd-0.5Zr magnesium alloys at different states

The microstructural evolution and mechanical properties of Mg-5Y-5Gd-xNd-0.5Zr magnesium alloys at different states were studied.The results reveal that island compounds at the grain boundaries of the as-cast alloys mainly were Mg24Y5,Mg41Nd5,and Mg5Gd phases.After homogenization at 808 K for 24 h,the distribution of the island compounds became discrete and Mg5Gd phases mostly decomposed and dissolved.With hot extrusion,the grain size was refined to about 20 μm on average,and both the strength and elongatio...     

Nd对铸态及轧制态Mg-Zn-Y合金组织及性能的影响

在Mg-3.5Zn-0.6Y合金中添加不同含量(0、0.4%、0.8%、1.2%)的稀土元素Nd,研究其对Mg-3.5Zn-0.6Y合金铸态及轧制态显微组织与力学性能的影响。结果表明,添加0.4%、0.8%的Nd的合金晶粒较细小,呈等轴晶,并且含有Mg41Nd5和Mg24Y5相。镁合金在热轧时第二相被破碎,晶粒变得更加细小。铸态合金经400℃×12h扩散退火,轧制态合金经400℃×0.5h退火后抗拉强度及伸长率最大,分别为234MPa、14.6%和265MPa、11.7%。     

Microstructure and mechanical properties of extruded Mg-6.5Gd-1.3Nd-0.7Y-0.3Zn alloy

The Mg-6.5Gd-1.3Nd-0.7Y-0.3Zn alloy ingot and sheet were prepared by casting and hot extrusion techniques,and the microstructure,age hardening behavior and mechanical properties were investigated.The results show that the as-cast alloy mainly containsα-Mg solid solution and compounds of Mg5RE and Mg24RE5(RE=Gd,Y and Nd)phases.The grain size is refined after hot extrusion,and the Mg5RE and Mg24RE5 compounds are broken during the extrusion process.The extruded alloy exhibits remarkable age hardening response and excellent mechanical properties in the peak-aging state.The ultimate tensile strength,yield strength and elongation are 310 MPa,201 MPa and 5.8%at room temperature,and 173 MPa,133 MPa and 25.0%at 300℃,respectively.     

Ho对铸态Mg-5Y-3Sm-0.5Zr合金显微组织和力学性能的影响

采用光学显微镜、扫描电镜、X射线衍射仪、电子拉伸实验机、布氏硬度计等研究了铸态Mg-5Y-3Sm-xHo-0.5Zr(x=0,2,4,6)合金的组织和力学性能。结果表明:铸态Mg-5Y-3Sm-0.5Zr合金主要由α-Mg和大部分位于晶界的Mg24Y5和Mg41Sm5第二相组成。添加Ho后,在晶界处出现了Mg24Ho5新相,Ho的含量高低对合金相组成没有影响。随着Ho含量的不断提高,析出的第二相逐渐增多,晶粒尺寸逐渐减小。当Ho含量为4%时,该铸态合金的综合力学性能最好,抗拉强度、屈服强度、硬度和伸长率分别为193 MPa、170 MPa、72.8 HBW和4.15%。     

稀土镁合金铸造和挤压态组织及力学性能研究

制备了3种不同成分的镁-稀土合金,研究稀土(RE)元素铈(Ce)、钕(Nd)和钇(Y)对镁合金铸态组织、力学性能尤其是高温力学性能的影响.采用光学显微镜(OM)、扫描电子显微镜(SEM)及X射线衍射(XRD)仪等对3种镁-稀土合金组织及相组成进行了分析.稀土元素与镁形成的镁-稀土相分别为Mg12Ce、Mg17Ce2、Mg12Nd、Mg24Y5、Mg41Nd5,主要分布在铸态组织晶界.对3种合金的铸态试样进行了室温力学性能及高温力学性能试验,并与挤压态比较,结果显示:在镁合金中,Nd的强化作用优于Ce,在高温时,Nd和Y共同强化作用优于Nd.     

A comparative study of Mg-Gd-Y-Zr alloy cast by metal mould and sand mould

The differences of the microstructure and mechanical property between metal mould and sand mould cast Mg-10Gd-3Y-Zr alloy were investigated both under as-cast condition and after solution heat treatment.In the as-cast specimens,the microstructure is similar and composed of α-Mg solid solution and eutectic compound of α-Mg+ Mg24(Gd,Y) 5;whereas the grain size using metal mould and sand mould is 27 μm and 71 μm,respectively.The eutectic compound of metal mould cast alloy was completely dissolved after solution treated at 500℃ for 8 h,however it needs higher temperature(525 ℃) and longer time(12 h) to achieve the absolute dissolving under sand mould condition.In contrast to metal mould,the peak time of sand mould alloy aged at 225 ℃ and 250 ℃ of was advanced by 4 h and 6 h,respectively.The precipitation reaction sequence in sand mould cast Mg-10Gd-3Y-Zr alloy during isothermal ageing at 250 ℃ follows S.S.S.S.→β″(D019) →β'(cboc) →β1(fcc) →β(fcc) ,which is similar to that in the alloy cast using metal mould.     

Effect of Gd content on microstructure and dynamic mechanical properties of solution-treated Mg−xGd−3Y−0.5Zr alloy

The effect of Gd content ranging from 6.5 wt.% to 8.5 wt.% on microstructure evolution and dynamic mechanical behavior of Mg?xGd?3Y?0.5Zr alloys was investigated by optical microscopy, X-ray diffraction, scanning electron microscopy and split Hopkinson pressure bar. The microstructure of as-cast Mg?xGd?3Y?0.5Zr alloys indicates that the addition of Gd can promote grain refinement in the casting. Due to the rapid cooling rate during solidification, a large amount of non-equilibrium eutectic phase Mg₂₄(Gd,Y)₅ appears at the grain boundary of as-cast Mg?xGd?3Y?0.5Zr alloys. After solution treatment at 520 °C for 6 h, the Mg₂₄(Gd,Y)₅ phase dissolves into the matrix, and the rare earth hydrides (REH) phase appears. The stress?strain curves validate that the solution-treated Mg?xGd?3Y?0.5Zr alloys with optimal Gd contents maintain excellent dynamic properties at different strain rates. It was concluded that the variation of Gd content and the agglomeration of residual REH particles and dynamically precipitated fine particles are key factors affecting dynamic mechanical properties of Mg?xGd?3Y?0.5Zr alloys.     

微量Sc对Mg-7Gd-3Y合金组织及力学性能的影响

利用光学显微镜、扫描电镜和XRD,分析研究了微量Sc对Mg-7Gd-3Y铸态合金组织及其室温和200℃力学性能的影响.结果表明,在合金中加入0.5%的Sc,促进了Mg24(Y,Gd)5和Mg5(Gd,Y)相的析出,降低Gd在Mg24(Y,Gd)5相中的相对含量,合金的室温和200℃时的抗拉强度分别提高了25 MPa和18 MPa;屈服强度分别提高了28 MPa和22MPa;伸长率分别提高了18.3%和37.8%.     

Structural and corrosion characterization of biodegradable Mg–RE (RE=Gd,Y, Nd) alloys

Binary Mg–Gd (up to 5% Gd in mass fraction), Mg–Nd (up to 9% Nd in mass fraction) and ternary Mg–Gd-Y (up to 5% Gd, 1% Y) alloys with precisely determined contents of cathodic impurities (Fe, Ni, Cu, Co) were studied. The alloys were studied in the as-cast state (cooling rate of 500 K/min) and after solution heat treatment (T4). Structures were investigated by optical and scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction and glow discharge spectrometry. Structural investigation was completed by Vickers hardness measurements. Corrosion behavior in the simulated physiological solution (9 g/L NaCl) was assessed by immersion tests and potentiodynamic measurements. It was found that the structures of the as-cast alloys were dominated by fine α-Mg dendrites and eutectic Mg–RE phases. The dendrites exhibited RE-concentration gradients which were most pronounced in the Mg–Gd alloys. For this reason, the T4 heat treatment of the Mg–Gd alloy led to the formation of a new cuboidal Mg₅Gd phase. The corrosion resistance was significantly improved by Gd. The effect of Nd was weak and the addition of Y to Mg–Gd alloys had harmful effect on the corrosion resistance. The T4 heat treatment strongly accelerated the corrosion of Mg–Gd alloys. Its effect on the corrosion of Mg–Nd alloys was not significant. The observed corrosion behavior of the alloys was discussed in relation to their structural states and contents of cathodic impurities.     

Zn对Mg-10Gd-2Y-0.5Zr镁合金组织和性能的影响

通过在Mg-10Gd-2Y-0.5Zr合金中添加Zn,采用SEM、XRD及万能拉伸试验机,研究了Zn添加对其铸态组织和力学性能的影响。结果表明,Mg-10Gd-2Y-0.5Zr合金的铸态组织主要由α-Mg、Mg₅(Gd,Y)和Mg₂₄(Y,Gd)5相组成,而添加质量分数为0.5%~1.5%的Zn后,合金的铸态组织主要由α-Mg、Mg₅(Gd,Y,Zn)、Mg₂₄(Y,Gd,Zn)₅及Mg₁₂(Gd,Y)Zn相组成。添加0.5%的Zn后,合金的室温力学性能明显提高,当Zn含量高于1.0%后,镁合金的室温力学性能开始逐步降低。当Zn含量为0.5%时,合金具有较佳的综合力学性能,其抗拉强度、屈服强度和伸长率分别为197 MPa、160 MPa和4.37%。Zn对Mg-10Gd-2Y-0.5Zr合金铸态力学性能的影响与其铸态组织中Mg₅(Gd,Y,Zn)、Mg₂₄(Y,Gd,Zn)₅和Mg₁₂(Gd,Y)Zn第二相及其数量有关。     

Effects of yttrium on microstructure and mechanical properties of Mg-Zn-Cu-Zr alloys

The effects of yttrium addition on microstructure and mechanical properties of as-cast Mg-6Zn-3Cu-0.6Zr-xY(x=0,0.5, 1.0,1.5 and 2.0,mass fraction,%)(ZCK630+xY for short in this study)alloys were investigated by means of OM,XRD and SEM. The results show that the average grain size of Mg-Zn-Cu-Zr magnesium alloy is effectively reduced(from 57μm to 39μm)by Y addition.The analysis of XRD indicates the existence of I-phase(Mg3Zn6Y)and W-phase(Mg3Zn3Y2)in ZCK630 alloys with Y addition.The ultimate tensile strength of ZCK630 alloys is significantly deteriorated with increasing Y addition,which is possibly related to the continuous networks of intergranular phases and the increase of W-phase.     

高强Mg-Gd-Y-Zn-Zr合金的微观组织和力学性能

通过金属模铸、热挤压和时效处理(T5)工艺过程制备出高强Mg-7Gd-4Y-1.6Zn-0.5Zr合金,并利用光学显微镜、XRD、SEM及TEM分析研究Mg合金不同状态下的显微组织和力学性能。结果表明:Mg-7Gd-4Y-1.6Zn-0.5Zr合金的铸态组织主要由α-Mg基体和沿晶界分布的片层状第二相Mg12Zn(Gd,Y)组成,经过热挤压变形后,合金晶粒显著细化,时效处理过程中Mg12Zn(Gd,Y)相上析出少量细小的颗粒状Mg3Zn3(Gd,Y)2相。时效态合金的抗拉强度、屈服强度和伸长率分别达到446 MPa、399 MPa和6.1%,其强化方式主要为细晶强化和第二相强化。     

热处理对Mg-11Gd-3Y-0.8Ca-0.5Zr合金显微组织及性能的影响

采用光学显微镜、扫描电镜、X射线衍射仪、XHB-3000型布氏硬度计和万能电子拉伸实验机等研究了Mg-11Gd-3Y-0.8Ca-0.5Zr合金的最佳热处理工艺和热处理对合金显微组织及性能的影响。结果表明:合金的最佳固溶工艺为485℃×16 h+505℃×16 h,时效工艺为225℃×12 h。铸态合金主要由初生相α-Mg基体和大量处于晶界处网络状的Mg5Gd、Mg24Y5、Mg2Ca相组成。经固溶时效后,相种类没有变化,但晶界变得清晰,第二相的形貌显著改变,呈颗粒状和短棒状均匀分布在基体上,组织得到明显改善,合金的力学性能显著提高,时效态合金的抗拉强度、屈服强度及硬度均显著优于铸态合金,分别由原来的217 MPa、185 MPa和92 HB增加到265 MPa、228 MPa和121 HB,这主要归功于时效沉淀强化的作用。     

真空压铸Mg-6Gd-3Y-0.5Zr镁合金的组织与性能

采用真空压铸工艺制备GW63K合金,研究压射速度和真空度对组织及性能的影响。采用光学显微镜、SEM及EDX对组织进行观察。研究GW63K的热处理工艺。结果表明：铸态GW63K合金由α-Mg基体和Mg24（Gd,Y）5第二相组成,且随着压射速度的增加,合金的屈服强度没有大的变化,但是伸长率先增加后减小;真空辅助能够减少气孔的大小及含量。在475℃固溶2 h,然后在200℃下时效80 h,GW63K合金的抗拉强度和伸长率分别达到308 MPa和9.45%。首次发现预初晶（ESCs）的存在对压铸GW63K合金热处理性能有巨大影响,预初晶（ESCs）的存在严重降低热处理后合金的性能。     

Nd添加对AZ80镁合金显微组织及力学性能的影响(英文)

研究添加稀土元素Nd对AZ80镁合金显微组织及力学性能的影响。结果表明:添加1.0%Nd元素可以有效地改善AZ80合金的铸态组织,其晶粒尺寸由448μm细化至125μm,凝固组织中出现条状的Al11Nd3相和块状的Al2Nd相,且β-Mg17Al12相显著细化,由连续网状变为不连续分布。时效过程中Nd元素的添加抑制了晶界处不连续析出相的出现,并推迟合金时效峰值的出现。在AZ80合金中添加1.0%Nd时,合金的综合力学性能最佳,屈服强度、抗拉强度和伸长率分别为103.7MPa、224.0MPa和8.4%。该合金T6态的屈服强度和抗拉强度分别达到141.1和231.1MPa。     

Microstructure,mechanical properties,and corrosion resistance of Mg–9Li–3Al–1.6Y alloy

Mg–9Li–3Al–1.6Y alloys were prepared through mixture method. The microstructure, mechanical properties, and corrosion resistance of the as-cast and asextruded alloys were studied by optical microscopy(OM),scanning electronic microscopy(SEM), X-ray diffraction(XRD), mechanical properties testing, and electrochemical measurement. The as-cast Mg–9Li–3Al–1.6Y alloy with the average grain size of 325 lm is composed of b-Li matrix, block a-Mg, and granule Al_2Y phases. After extrusion, the grain size of the as-cast alloy is obviously refined and reaches to 75 lm; the strength and elongation of the extruded alloy are enhanced by 17.20 % and49.45 %, respectively, owing to their fine microstructure and reduction of casting defects. The as-extruded alloy shows better corrosion resistance compared to the as-cast one, which may be related to the low stored energy and dislocation density in the extruded alloy, also the homogenization treatment before extrusion.     

钆对Mg-8Li-4Zn-xGd合金铸态组织与力学性能的影响

采用锂盐熔剂保护熔铸Mg-8Li-4Zn-xGd(x=1,3,5)合金铸锭,研究钆含量对铸态合金组织和力学性能的影响。结果表明:Mg-8Li-4Zn-xGd合金基体由α-Mg(HCP)和β-Li(BCC)双相构成。随着钆含量的增加,Mg5Gd共晶相和Zn12Gd化合物相逐渐连成网状,将基体α+β双相隔离成20~40μm的等轴状或类似于铸铁中的共晶团状,可有效细化α-Mg相和连续的β-Li相;组织中大颗粒Mg2Zn11相弥散分布在β-Li相内,Mg51Zn20相分布在α-Mg晶界处;锌元素还可以在β-Li相中析出细小弥散分布的MgZn相,其数量随钆含量的增加而增加,可直接弥散强化β-Li相。此外,锌和钆对合金硬度的影响较大,随着钆含量的增加,合金的抗拉强度提高,但伸长率降低。     

热处理工艺对高真空压铸Mg–8Gd–3Y–0.4Zr镁合金组织及力学性能的影响

研究T4和T6热处理状态下高真空压铸Mg-8Gd-3Y-0.4Zr（质量分数,%）合金的微观组织、化合物含量、力学性能及断裂行为。铸态Mg-8Gd-3Y-0.4Zr合金微观组织主要由α-Mg和共晶Mg24（Gd,Y）5化合物组成。经固溶处理后,共晶化合物大量溶解于镁基体,合金主要含过饱和α-Mg及方块相。固溶合金中方块相的含量随固溶温度的升高而增大,力学性能也有所提高。根据微观组织结果,确定475℃,2 h为Mg-8Gd-3Y-0.4Zr合金最优固溶方案。合金的最佳屈服强度为222.1 MPa,延伸率可达15.4%。铸态,T4状态下和T6状态下合金的拉伸断裂模式为穿晶准解理断裂。     

Effect of microstructure on tensile and fatigue properties of cast Mg–10Gd–2Y–0·5Zr alloy

Abstract

The microstructure and its effect on tensile properties and fatigue properties of a Mg–10Gd–2Y–0·5Zr (wt-%) cast alloy have been studied. The microstructures of as-cast, solution treated and T6 treated specimens were examined by optical and scanning electron microscopy (SEM). Tensile properties and fatigue properties of the specimens were determined and fractography was carried out. The SEM examination showed that the precipitates after T6 treatment were mainly distributed at grain boundaries, which accounts for the intergranular brittle fracture observed. The average grain size of the specimens measured after solution treatment varied from 87 to 128 μm. The mechanical tests showed that the tensile strength and low cycle fatigue strength increase with decreasing average grain size, whereas high fatigue strength is less sensitive to grain size. The fractography indicated that ductile and brittle fracture patterns coexist.