Effects of yttrium on microstructure and mechanical properties of Mg-6Al magnesium alloy

Since Y has a great solid solubility in magnesium alloys, it helps enhancing the heat-resistant property of magnesium alloys. The effects of Y on microstructures and mechanical properties of Mg-6Al alloy have been studied in this work. The results show that Y addition refines grains of Mg-6Al alloy, and reduces the amount of the Mg 17 Al 12 phase. At the same time, the high melting-point Al 2 Y phase particles are formed. According to the mathematical model of the two-dimensional lattice misfit proposed by Braffit, it is believed that the Al 2 Y particles can serve as the nucleation sites for α-Mg. After T6 treatment, both elongation and ultimate tensile strength of Mg-6Al alloy at the room temperature and high-temperature increased firstly and then decreased, with increasing Y addition. The peak mechanical properties were achieved in the Mg-6Al-1.2Y alloy system. Y addition appears to change the fracture characteristic of Mg-6Al alloy. With 1.2wt%Y, the fracture surface of the alloy showed a lot of dimples and tearing ridges which connected the microscopic dimples and the fracture is mixed fracture of quasi-cleavage and ductile fracture.     

热处理工艺对Mg-6Zn-2.5Cu镁合金显微组织和力学性能的影响

利用光学显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)、X射线衍射仪(XRD)和力学试验机等研究了铸造Mg-6Zn-2.5Cu合金在铸态、固溶和时效处理下的显微组织和力学性能。结果表明:合金的铸态组织主要由α-Mg和(α-Mg+MgZn2+Mg2Cu+CuZnMg)共晶相组成。在455℃固溶12~36 h时,随着时间增加,固溶效果逐渐增强,且在20 h时合金获得了较理想的显微组织及218 MPa的抗拉强度和8.68%的伸长率。随后在180℃时效6~72 h后,合金的拉伸性能随时效时间的增加呈先增加后减小的趋势,其中时效24 h时后,合金的抗拉强度和硬度达到峰值,分别为249.5 MPa和64.6 HV0.1,比铸态的分别提高了66.5 MPa和26.29%,伸长率在时效12 h时后达到了峰值6.72%。铸态合金的断裂方式以沿晶断裂为主,时效处理后合金的断裂方式为准解理断裂。     

RE元素Y和Nd对Mg-6Al合金显微组织的影响

研究了RE元素Y和Nd元素对Mg-6Al镁合金在铸态和固溶热处理状态下显微组织的影响。金相显微镜、扫描电镜及电子探针分析结果表明，Y和Nd稀土元素均有促进Mg-6Al合金铸态组织晶粒细化的作用，添加质量分数为0．5％的Y元素可使合金的晶粒尺寸由Mg-6Al合金的102．00μm细化至76．92μm，加入质量分数为1％的Nd后合金晶粒尺寸为65．79μm，而且Y和Nd在复合加入时，细化效果更为显著，晶粒尺寸为57．47μm。Y和Nd与合金中的铝元素形成热稳定性较高的块状YAl2相和条状NdAl2相，两者在α-Mg晶粒内和晶界均有分布。     

Mg-10Y-1.5Sm合金的组织和力学性能

采用合金熔炼、组织分析和拉伸试验,研究了Mg-10Y-1.5Sm合金经过固溶时效后的组织和力学性能.结果表明,合金的组织由α-Mg基体和Mg24Y5相组成,细小的Mg24Y5颗粒相均匀弥散地分布在α-Mg基体上;Sm加入后没有形成新相,而是通过固溶作用,进一步强化了α-Mg基体和Mg244Y5相;合金在200～300℃之间的抗拉强度均大于200 MPa,伸长率均为3%左右,与室温时相比没有发生显著变化;合金的力学性能优于Mg-10Y合金,最高使用温度可达350℃.     

往复挤压Mg-4Al-4Si镁合金的显微组织与力学性能

研究往复挤压对Mg-4Al-4Si(AS44)合金显微组织和性能的影响。结果表明:往复挤压显著地细化晶粒,改善组织的均匀性;往复挤压4道次和8道次后,Mg2Si颗粒尺寸由铸态下的约120μm分别减小至3和2μm,α-Mg基体晶粒尺寸由铸态下的约50μm分别减小至9和8μm,形成了较为细小、弥散分布的Mg2Si颗粒和细小的等轴晶组织。合金的力学性能随往复挤压道次的增加而显著提高,挤压8道次时,合金的极限抗拉强度、屈服强度和伸长率分别达到251.7 MPa、210.5 MPa和14.8%,与铸态合金相比,上述力学性能指标分别提高了131.3%、191.1%和469.2%;挤压态合金拉伸断裂形式为微孔聚合型韧性断裂。     

Microstructure and mechanical properties of die-cast AZ91D magnesium alloy by Pr additions

Mg-9Al-xPr (x=0.4, 0.8 and 1.2, mass fraction, %) magnesium alloys were prepared by high-pressure die-casting technique. The effects of Pr on the microstructures of die-cast Mg-9Al based alloy were investigated by XRD and SEM. Needle-like Al11Pr3 phase and polygon Al6Mn6Pr phase are found in the microstructure. With 0.4% Pr addition, fine needle-like Al11Pr3 phase and a small amount of polygon Al6Mn6Pr phase near the grain boundary are found in the microstructure. Increasing Pr addition to 0.8%, lots of coarse needle-like Al11Pr3 phase within grain and polygon Al6Mn6Pr phase on grain boundary are observed. Further increasing Pr addition, the size of needle-like Al11Pr3 phase decreases, while the size of polygon Al6Mn6Pr relatively increases. The mass fraction of Pr at around 0.8% is considered to be suitable to obtain the optimal mechanical properties. The optimal mechanical properties are mainly resulted from grain boundary strengthening obtained by precipitates and solid solution.     

Nd对Mg-6Zn微观组织影响研究

采用熔铸法制备了Mg-6Zn和Mg-6Zn-xNd合金,利用扫描电镜及所带的能谱分析仪,研究了Nd含量对铸态Mg-6Zn-xNd的微观组织的影响,结果表明：Mg-6Zn合金基体上存在着α-Mg和Mg-Zn相的共晶团,添加Nd元素后合金基体上出现Mg-Zn-Nd三元共晶组织,这些共晶组织数量随着Nd含量增加而增加,最终形成含有Mg,Zn,Nd三种元素的连续网状结构。     

汽车用铸造镁合金的组织与力学性能

研究了Sr含量和振动凝固振幅对铸造AM50-Y镁合金组织与力学性能的影响。结果表明,随着振幅的增加,铸态镁合金的晶粒尺寸不断减小,组织中的块状或者条状相逐渐演变为点状弥散分布,合金的抗拉强度、屈服强度和伸长率逐渐上升,振幅为2.5 mm时达到极大值。随Sr含量增加,振幅为2.5 mm合金的晶粒尺寸比未振动合金要小,抗拉强度、屈服强度和伸长率增大。     

Mg-2Al-xSi合金显微组织与性能的试验研究

采用重力铸造法制备Mg-2Al-xSi(x=0.50、0.75、1.0和1.25)镁合金,研究其铸态合金的显微组织和性能。结果表明,铸态Mg-2Al-xSi合金主要由α-Mg基体、β-Mg17Al12和Mg2Si相组成。当w(Si)<1.0%时,随着Si含量增加,汉字状Mg2Si相的平均尺寸逐渐减小,从Mg-2A1-0.50Si合金的65μm减至Mg-2A1-1.00Si合金的38μm。块状Mg2Si相的平均尺寸随着Si含量的增加而逐渐增加,从Mg-2A1-0.75Si合金的14μm增至Mg-2Al-1.25Si合金的36μm。合金的显微硬度随着Si含量的增加而逐渐升高,由Mg-2A1-0.50Si合金的HV48.6增至Mg-2Al-1.25Si合金的HV59.1。Mg-2A1-0.75Si合金具有较好的常温和高温性能:常温时的抗拉强度和伸长率分别是145 N/mm2和7.0%,高温(423 K)时的抗拉强度和伸长率分别是130 N/mm2和10.0%,断裂特征为准解理断裂。     

含钇Mg-6Al镁合金组织和高温力学性能

研究了稀土元素Y(0～2.4wt%)对Mg-6Al合金显微组织和力学性能的影响.结果表明,添加稀土元素Y可以显著提高时效态合金从室温至200℃区间的拉伸屈服强度和抗拉强度.在Mg-6Al合金中加入0.6wt%～2.4wt%的Y后,合金的显微组织均得到细化,Al2Y高熔点点状稀土合金相产生.在本研究的范围内,加入1.2wt%Y的合金从组织到性能各项性能最优.     

Mg-5.5Al-0.5Y-xSm合金的显微组织和力学性能

采用XRD、OM、SEM和EDS等手段研究了Mg-5.5Al-0.5Y-xSm(x=0~2.0%)合金的显微组织和力学性能。实验结果表明,加入适量的Sm后,合金晶粒和Al2Y相得到细化,Mg17Al12相数量减少,同时基体中出现高熔点相Al2Sm相。随着Sm含量的增加,合金的室温(25℃)和高温(150℃和175℃)力学性能先升高后降低,且在Sm含量为1%时达到最佳。     

Microstructure and mechanical properties of Al–Si alloy modified with Al–3P

Al–Si alloy was modified with Al–3P master alloy at 740 °C. The effects of Si content (7, 8, 9, 10 and 11 wt.%) and adding amount of alterant Al–3P (0, 0.1, 0.3, 0.6, 1.0 and 1.5 wt.%) on microstructures and tensile properties of the alloy were investigated with optical microscope (OP), Image Pro Plus 6.0, scanning electron microscope (SEM) and universal testing machine. When the content of Al–3P is 0.6 wt.%, the area fraction of primary α(Al) in the Al–Si alloy increases more compared to the unmodified alloy with an increase in Si content, which could be explained by the movement of non-equilibrium eutectic point. When the Si content is constant (Al–10Si), with the increase of Al–3P content, the increased rate in area fraction of primary α(Al) phase in the Al–10Si alloy increases first and then decreases. And when 0.6 wt.% Al–3P is added, the increase in area fraction of primary α(Al) phase is the largest. Compared to the unmodified Al–10Si alloy, the tensile strength and elongation of Al–10Si alloy increase by 2.3% and 47.0%, respectively, after being modified with 0.6 wt.% Al–3P alloy. The fracture mode of the modified Al–10Si alloy is ductile fracture.     

Effects of erbium on microstructure and mechanical properties of as-cast Mg-7Zn-3Al alloy

Mg-7Zn-3Al-xEr(x=0.1,0.4,0.7) magnesium alloys were prepared by permanent mould casting.The effects of rare earth element of erbium on the microstructure and mechanical properties of as-cast Mg-7Zn-3Al alloy at both room temperature and elevated temperatures were investigated with optical microscopy,scanning electron microscopy/energy dispersive X-ray spectroscopy,differential scanning calorimetry,and tensile testing.The results show that the quasi-continuous grain boundary networkedτ(Mg_(32)(Al,Zn)_(49)...     

Mg-2Nd合金的组织与抗蠕变性能

研究了Mg-2Nd合金的铸态显微组织、力学性能和抗蠕变性能。结果表明:Mg-2Nd合金的铸态组织由α-Mg基体和分布于晶界的离异共晶相Mg12Nd组成;铸态Mg-2Nd合金的抗拉强度和屈服强度随温度的增加而下降,但下降的幅度不大,具有较好的高温稳定性,伸长率则随温度增加明显上升;铸态Mg-2Nd合金表现出良好的抗蠕变性能。通过计算,合金在150～250℃、30～110MPa下的应力指数为3.3～8.0,蠕变激活能在108～142kJ/mol的范围。合金的蠕变机制归结于位错攀移控制,晶界滑移起一定的作用。     

热挤压AZ80镁合金管材的组织与力学性能

对AZ80镁合金管材的挤压工艺进行研究,对挤压前后材料的组织与力学性能进行分析。结果表明,经过热挤压后,镁合金的晶粒细化,力学性能有较大提高。晶粒尺寸由挤压前铸态的28μm细化到挤压后的4μm,抗拉强度由162 MPa提高到265 MPa,屈服强度由74 MPa提高到180 MPa,伸长率由4%提高到14%。随着挤压比的增加,晶粒细化明显,伸长率和屈服强度增加。对于挤压AZ80镁合金管材,合理的挤压工艺参数：挤压比为18.2,坯料温度为390℃,模具预热温度为360℃,挤压速度为1 mm/s,凹模锥半角为60°-70°。     

往复挤压AM60B镁合金的组织与力学性能

通过往复挤压（CEC）变形来细化AM60B镁合金的组织。结构表明：随着CEC道次的增加,组织得到明显细化。当材料达到临界最小晶粒尺寸时,进一步挤压变形也很难使组织得到明显的细化。细小的组织具有优异的力学性能,合金的硬度、屈服强度、抗拉强度和断后伸长率分别由铸态的62．3、64MPa、201MPa和11％上升N-道次变形后的72．2、183．7MPa、286．3MPa和14．0％。但是再进一步挤压变形材料的力学性能增加幅度不明显,经四道次挤压变形后其硬度、屈服强度、抗拉强度和断后伸长率分别为73．5、196MPa、297MPa和16％     

初始组织对热挤压Mg-6Al-2Ca-2Sm合金显微组织和力学性能的影响

对铸态Mg-6Al-2Ca-2Sm合金分别进行经固溶和固溶+时效处理获得不同初始组织试样,然后对不同初始组织的试样进行热挤压,研究了不同初始组织对热挤压Mg-6Al-2Ca-2Sm合金显微组织和力学性能的影响。结果表明：铸态合金经热挤压后发生明显的部分再结晶,显微组织得到显著细化;经固溶或固溶+时效处理能够改善合金组织,热挤压后合金显微组织分布更加均匀。初始组织分布能够改善热挤压Mg-6Al-2Ca-2Sm合金室温和高温力学性能,固溶+时效后进行热挤压,Mg-6Al-2Ca-2Sm合金具有最高的抗拉强度和延伸率。     

Microstructure and mechanical properties of AZ81 magnesium alloy with Y and Nd elements

The effects of rare earth（RE） elements Y and Nd （w（Y）/w（Nd）=3：2） with total content of 1%-4% on microstructures and elevated temperature mechanical properties of AZ81 magnesium alloy were investigated. The results show that, proper content of rare earth elements makes the microstructures of AZ81 magnesium alloy refine obviously and the quantity offl-MglTAll2 phases reduce, and Al2Y and Al2Nd form. After solid solution treatment, with increasing content of rare earth elements, the tensile strength and elongation of the alloys （at room temperature, 150 ℃ and 250 ℃） increase first, then decrease. When the content of rare earth elements is up to 2%, the values of tensile strength at room temperature and 150 ℃ are up to their maxima simultaneously, 282 MPa and 212 MPa, respectively. Meanwhile, the values of elongation at room temperature and at elevated temperature are also up to their maxima, 13% and 15%, respectively.     

Effects of Cu addition on microstructure and mechanical properties of as-cast Mg-6Zn magnesium alloy

The application of Mg-Zn binary alloys is restricted due to their developed dendritic microstructure and poor mechanical properties. In this study, an alloying method was used to improve the mechanical properties of Mg-Zn alloy. The Mg-6Zn magnesium alloys microalloyed with varying Cu content(0, 0.8, 1.5, 2.0 and 2.5wt.%) were fabricated by permanent mould casting, and the effects of Cu content on the microstructure and mechanical properties of as-cast Mg-6Zn alloys were studied using OM, SEM, XRD and tensile tests at room temperature. The obtained results show that the addition of Cu not only can refine the grains effectively, but also can modify the eutectic morphology and improve the mechanical properties of the alloys. The main phases of the studied alloys include α-Mg, MgZn_2, Mg_2Cu and CuMgZn. When the content of Cu exceeds 0.8wt.%, Mg_2Cu phase appears. Meanwhile, the eutectic morphology is modified into dendritic shape or lamellar structure, which has an adverse effect on the tensile properties. Furthermore, among the investigated alloys, the alloy containing 0.8% Cu shows an optimalultimate tensile strength of 196 MPa, while the alloy with 1.5wt.% Cu obtains an excellent elongation of 7.22%. The experimental alloys under different Cu contents show distinguishing fracture behaviors: the fracture of the alloy with 0.8wt.% Cu reveals a mixed mode of inter-granular and quasi-cleavage, while in other investigated alloys, the fracture behaviors are dominated by cleavage fracture.     

Mg-2Nd合金的组织与力学性能

在铸钢坩锅中熔炼制备了Mg-2Nd二元镁合金,试样经不同热处理工艺处理后,测试合金的室温拉伸性能,采用光学显微镜（OM）、扫描电镜（SEM）及透射电镜（TEM）观察合金的显微组织,通过X射线衍射法（XRD）和能谱分析（XEDS）及选区电子衍射花样进行合金中的物相鉴别和微观成分分析。结果表明：Mg-2Nd合金的铸态组织由α-Mg基体和呈离异共晶形貌的Mg12Nd相组成;热挤压后,Mg12Nd相沿挤压方向呈纤维或颗粒状分布;挤压过程中发生动态再结晶,合金的抗拉强度（σb）由铸态的148.8 MPa提高到挤压态的210.2 MPa,伸长率（δ）由铸态的2.8%提高到挤压态的19.9%;热挤压和热轧成形的Mg-2Nd合金,直接时效T5（extruded、rolled）处理能产生形变强化和时效硬化双重作用,其中T5（rolled）态合金σb高达276.4 MPa,δ较热轧态提高了64%;T5（rolled）态组织中出现了β′和β沉淀,尺度均在50 nm左右,对合金产生了明显的时效强化作用。