Cu对Mg-7Zn-0.6Zr合金流动性的影响

使用流动性模具研究了Cu含量对Mg-7Zn-x Cu-0.6Zr(x=0,1,2,3)合金流动性的影响。用双电偶差热分析法分析了合金凝固过程中的凝固区间和枝晶相干温度等参数,根据TEM鉴别了合金的微观物相,并结合SEM和EPMA观察了合金的显微组织。基于理论预测和流动性实验测试研究了Mg-7Zn-x Cu-0.6Zr(x=0,1,2,3)合金的流动性。结果表明,随着Cu的加入在Mg-7Zn-0.6Zr合金中析出MgZnCu共晶组织,使晶粒细化、凝固区间减小、枝晶相干温度降低、枝晶生长速率降低和合金流动性提高。     

挤压GW102镁合金组织和力学性能

研究了Mg-9.8Gd-1.6Y-0.02Zn-0.5Zr(GW102)镁合金挤压棒材的显微组织和不同方向的拉伸性能。结果表明,经520℃均匀化处理的GW102镁合金的组织主要由过饱和镁固溶体、少量凝固期间析出的颗粒相Mg5(Y0.6Gd0.4)和非平衡相Mg3(Gd0.5,Y0.5)组成。挤压变形并在200℃时效热处理60 h后,从过饱和固溶体中弥散析出大量针片状β″相和β′相。该镁合金经过挤压变形后具有明显的各向异性,垂直挤压方向合金的抗拉强度显著低于挤压方向的抗拉强度和延伸率。GW102合金的强化,其主要原因是长周期结构相(LPSO)与位错的相互作用和晶界上无沉淀析出带的影响。     

Zr微合金化对稀土镁合金微观结构和力学性能影响的电子显微学研究

微量Zr的添加不仅能够细化镁合金的晶粒,改善铸造性能,还会影响镁合金在热处理过程中微观结构的演变。利用多种电子显微学技术系统研究了Zr微合金化影响Mg-Zn-Nd镁合金力学性能和微观结构演变的机理。研究表明,含有微量Zr的Mg-2.7Nd-0.6Zn-0.5Zr镁合金经798 K固溶处理后,大量纳米Zn-Zr相的析出显著提升了该合金的显微硬度。在系列微束电子衍射分析的基础上,结合多方向原子分辨率结构和成分分析,确定了这些纳米Zn-Zr相为简单四方结构的Zn₂Zr₃相(空间群：P4₂/mnm,a=b=0.761 nm,c=0.682 nm),并重构出其原子构型。此外,研究结果还表明固溶处理过程中形成的纳米尺寸Zn₂Zr₃相,降低了基体中Zn元素的含量,显著提升了强化效果较好的柱面析出相β₁-Mg₃Nd的比例,进而提高了合金峰时效后的强度。研究结果丰富了Zr影响镁合金微观结构和力学性能机理的研究。     

热处理对GWZ661变形镁合金组织与性能的影响

采用常规铸造和热形变相结合的工艺制备Mg-6Gd-6Y-1Zn四元镁合金,并对其显微组织和力学性能进行较系统的研究。结果表明:合金的铸态组织主要由α-Mg,Mg24(GdYZn)5和具有18R-LPSO结构的Mg12Y1Zn1相组成。合金热挤压过程中Mg12Y1Zn1相被拉长,呈长条状沿挤压方向排列,而14H-LPSO相则分布于Mg12Y1Zn1相之间。挤压态合金在高温固溶处理后,Mg12Y1Zn1相溶入基体,而基体中的14H-LPSO相增加。挤压态合金经固溶和时效(T6)处理后,显微组织中呈现18R-LPSO,14H-LPSO结构和β′沉淀颗粒共存。对挤压后的合金直接进行时效(T5)处理过程中也发生了β′沉淀,但14H-LPSO相体积分数没有T6态多。合金在T6态的性能最好,强度和塑性达到了良好的匹配。     

Mg-11Y-5Gd-2Zn-0.5Zr(wt.%)合金的显微组织和力学性能

采用光学显微镜(OM)、带能谱分析(EDAX)的扫描电子显微镜(SEM)、X射线衍射仪(XRD)等方法对Mg-11Y-5Gd-2Zn-0.5Zr(WGZ115)合金的原始铸态(F态)、固溶处理态(T4态)和峰值时效态(T6态)的组织结构进行了分析。研究表明:F态WGZ115合金主要由基体(-αMg)、晶间共晶相(Mg24(YGdZn)5)和长周期结构相(Mg12Y1Zn1)组成。T4态WGZ115合金主要由基体相(-αMg)、长周期结构相(Mg12Y1Zn1)和少量分布于晶界附近的方块相(Mg-Y-Gd方块相)组成。T6态WGZ115合金的形貌与T4态相似,圆形的富Zr相始终存在于三种状态的合金中。通过不同温度下的拉伸实验发现T4态WGZ115合金的抗拉强度和塑性好于F态合金。而T6态合金的力学性能最好,在200℃时抗拉强度达到最大值341.1MPa。     

铸造镁合金Mg-Zn-Y-Zr-Ca在模拟体液中的腐蚀行为

采用光学显微镜和扫描电子显微镜研究了铸态Mg-3Zn-0.6Y-0.5Zr-0.3Ca(质量分数/%)合金的显微组织,采用失重法测试了合金在模拟体液中浸泡不同时间的生物腐蚀性能,并对合金的腐蚀行为进行分析。结果表明,Mg-3Zn-0.6Y-0.5Zr-0.3Ca合金中沿晶界连续分布的Mg3YZn6相对合金的腐蚀具有作为微阴极加速基体腐蚀或抑制腐蚀扩展的双重作用。Mg-3Zn-0.6Y-0.5Zr-0.3Ca合金的腐蚀过程分为3个阶段:晶界附近溶质原子贫化区形成几微米宽的腐蚀凹槽,在富Zr-贫Zr区形成大量腐蚀斑点,腐蚀凹槽和腐蚀斑点相互扩展破坏基体。     

高强高韧Mg-8.5Gd-2.0Y-1.0Ag-0.4Zr合金的组织与性能

研究了高强高韧Mg-8.5Gd-2.0Y-1.0Ag-0.4Zr(wt.%)合金的显微组织和力学性能。结果表明,该合金铸态组织细小,主要由α-Mg固溶体、晶界析出相Mg5(GdY)以及分布在晶粒内部的Zr核组成;T4态时晶界析出相基本完全消失,但出现了一些方块相γ;合金具有明显的时效硬化效果,且随着时效温度的提高,合金的峰值时效硬度下降,峰值时间相应缩短。经200℃峰值时效处理后表现出极为优异的室温力学性能,抗拉强度(UTS)和延伸率分别达到396MPa和9.1%,显著的时效强化是该合金具有优异力学性能的主要原因。如此优异的强度和塑性在常规铸造镁合金中是极为罕见的,对于推广镁合金的应用具有重要意义。     

时效Mg-8.14Zn-1.44Y-0.5Zr合金高温摩擦磨损性能研究

镁合金在航空航天、汽车及通讯领域有着广泛的应用, 为进一步改善镁合金的耐磨性,在不同温度下对Mg-8.14Zn-1.44Y-0.5Zr合金进行了时效处理,并测试了铸态和时效态合金的硬度及高温条件下摩擦磨损行为.采用扫描电子显微镜对不同载荷及环境温度条件下合金的摩擦磨损表面进行观察,并分析了其磨损机制.结果表明：在240 ℃时,随着时效时间的增加,合金的硬度值呈现先增加而后降低的趋势,当时效温度为240 ℃,时间为12 h时,Mg-8.14Zn-1.44Y-0.5Zr合金具有最高的硬度值; 铸态合金的磨损体积损失明显高于时效态合金,两种合金的磨损体积损失均随载荷和环境温度增加而增大,且时效态合金发生严重磨损时对应的转变温度滞后于铸态合金; 环境温度低于250 ℃时,合金的磨损机制主要为磨粒磨损和氧化磨损,环境温度为300 ℃时,磨损机制变为剥层磨损和黏着磨损.时效处理可显著提高Mg-8.14Zn-1.44Y-0.5Zr合金的硬度及耐磨性.     

Cu-Cr-Zr-Mg合金时效组织与性能

为了研究时效工艺对Cu-0.3Cr-0.15Zr-0.05Mg合金显微组织及性能的影响,在时效温度400～650℃和时效时间1～11h条件下,得到时效工艺参数与硬度和电导率的曲面关系,并利用透射电镜分析合金时效后的微观形态和析出相.研究结果表明:合金固溶后470℃时效4 h,硬度和电导率可达HV108和45 S·m-1,析出相为Cr、Cu4Zr和有序的CrCu2(Zr,Mg)相;550℃时效1 h后硬度和电导率仍具有HV106和46.8 S·m-1,析出相完全转变为Cr和Cu4Zr.     

高锌镁合金化学镀镍磷初始沉积特征的研究

化学镀Ni-P能提高镁合金的耐蚀性.采用金相观察、X射线衍射(XRD)、扫描电子显微镜(SEM)、能谱(EDS)等技术研究了铸态和固溶态Mg-8Zn-4Al合金化学镀Ni-P合金初始沉积的特点.结果表明:由于镁基体中α固溶体,(Al2Mg5Zn2),τ[Mg32(Al,Zn)49]相的组成元素存在差别,造成了相间的电极电位存在差异,初生的镍离子优先在相和τ相上沉积;随后以最先沉积的点为中心向四周扩展,以胞状形式生长;经过固溶的Mg-8Zn-4Al合金组织主要为过饱和α固溶体,相和τ相析出效果不明显,镍离子的初始沉积变得较为均匀,沉积速度有所减缓.     

Dynamic degradation behavior of MgZn alloy in circulating m-SBF

A test platform was designed to mimic the conditions that an implanted coronary stent encounters in coronary arteries, and the degradation behavior of a biodegradable MgZn alloy in the circulating modified simulated body fluid (m-SBF) was investigated on the platform. Results indicated that the presence of circulating solution over the surface of the specimen increased its corrosion rate compared to that in static immersion test, and the diffusion of Mg²⁺ and other ions dominated the corrosion mechanism of the alloy. A corrosion layer with randomly scattering particles conglomerated to clusters on its surface was observed after 168 h of measurement. While the amount of Mg decreased from the matrix to the corrosion layer, the concentration ratio of Zn did not have a significant change. The concentrations of calcium and phosphor seemed to be gradually increased with the extension of distance from MgZn matrix to the degradation layer.     

Ce对Al-Zn-Mg-Cu合金亚快速凝固铸造组织的影响

通过XRD,DSC,SEM,EDS等现代分析方法,研究了稀土元素Ce在不同凝固冷却速率下对Al-Zn-Mg-Cu合金显微组织、凝固温度的影响,分析讨论了Ce对合金晶粒细化和熔体净化作用的原理。结果表明,合金的主要析出相为α-Al和MgZn_2型共晶相,MgZn_2固溶了Al,Cu,Mg等元素并形成了Mg(Zn,Cu,Al)_2相,在晶界上溶质元素浓度较高,与α-Al基体共晶形成层片状共晶组织。添加Ce能使合金枝晶间距减小,并减小共晶层片间距和细化共晶组织,显著细化晶粒,并抑制铝合金中的杂质相Al7Cu2Fe的出现。Ce还将合金α-Al基体和共晶相的析出温度分别降低了6.4℃和5.6℃。     

Effect of Hot Deformation on Microstructure and Hardness of In-situ TiB2/7075 Composite

［1］P.Davies and J.L.F.Kellie: London and Scandinavian Co. Limited: Patent WO 93/05189, 1993. ［2］C.Bartels,D.Raabe,G.Gottstein and U.Huber:Mater. Sci. Eng., 1997, A237, 12.     

Microhardness,Microstructure and Electrochemical Efficiency of an Al(Zn/xMg) Alloy after Thermal Treatment

The influence of Mg on the microhardness,microstructure and electrochemical efficiency of Al(Zn/xMg) alloys have been investigated.Al(Zn/xMg) alloys were prepared by metal mould casting method to diminish the process cost and to generate an alloy with homogenous microstructure and less casting porosity.Vickers hardness,X-ray diffraction,scanning electron microscopy and transmission electron microscopy were performed to determine the Mg influence on the AlZn alloy.Electrochemical efficiency was used to relate the influence of Mg with the thermal treatment on the corrosion behavior of the Al(Zn/xMg) alloy.The results reveals the presence of Al 32(MgZn) 49 phase for two events;the first is when the Mg content is above 5.49% in as-cast condition,and the second after the thermal treatment is carried out at 450℃ for 5 h.The results also show that the microhardness and electrochemical efficiency have been influenced by the presence of Al 32(MgZn) 49 phase.The addition of Mg modifies the microstructure,increases the content of Al 32(MgZn) 49 phase and improves the electrochemical efficiency.     

Microstructure and Mechanical Properties of Ti-35V-15Cr-0.05C Nonburning Titanium Alloy

Ti-35V15Cr-0.05C is a new nonburning titanium alloy. The structural analyses show that the alloy consists of β phase and lath-like α phase distributed within β grains, and some titanium carbide particles appear at grain boundaries. Using dark field TEM method, it was also found that TiCr2 phase uniformly precipitates in α phase. After heat treatment at 900℃ for 15 min,equiaxed β phase of 60~ 80μm in diameter and lath-like α phase of 1-2% volume fraction were observed. This alloy possesses attractive mechanical properties.     

Microstructure and mechanical properties of a sand-cast Mg–Nd–Zn alloy

The microstructures and mechanical properties of a sand-cast Mg–Nd–Zn alloy in the as-cast, solution-treated and peak-aged conditions were investigated. The as-cast alloy was comprised of α magnesium matrix and Mg₁₂Nd eutectic compounds. The eutectic compounds dissolved into the matrix and small Zr-containing particles precipitated at grain interiors, due to the solution treatment. After the solution treatment, two kinds of cooling manner, either cooling in air or quenching in water, were employed. It was worth noting that some basal precipitates formed in the matrix during the in-air cooling process after solution treatment, which led to the succedent weak ageing hardening response and low strength in peak-aged condition. The hardness, yield strength, ultimate tensile strength and elongation at room temperature, of the samples in the T61 condition, were HV81, 191 MPa, 258 MPa and 4.2%, respectively. When tensile tested at high temperature, they exhibited serrated flow. Moreover, the casting surface of the tensile testing bar also had a great influence on its mechanical properties.     

Microstructure and mechanical properties of novel Al-Y-Sc alloys with high thermal stability and electrical conductivity

The microstructure and mechanical properties of novel Al-Y-Sc alloys with high thermal stability and electrical conductivity were investigated.Eutectic Al3 Y-phase particles of size 100-200 nm were detected in the as-cast microstructure of the alloys.Al3 Y-phase particles provided a higher hardness to as cast alloys than homogenized alloys in the temperature range of 370-440℃.L12 precipitates of the Al3(ScxYy) phase were nucleated homogenously within the aluminium matrix and heterogeneously on the dislocations during annealing at 400℃.The average size of the L12 precipitates was 11±2 nm after annealing for 1 h,and 25-30 nm after annealing for 5 h,which led to a decrease in the hardness of the Al-0.2 Y-0.2 Sc alloy to15 HV.The recrystallization temperature exceeded 350℃and 450℃for the Al-0.2 Y-0.05 Sc and Al-0.2 Y-0.2 Sc alloys,respectively.The investigated alloys demonstrated good thermal stability of the hardness and tensile properties after annealing the rolled alloys at 200 and 300℃,due to fixing of the dislocations and grain boundaries by L12 precipitates and eutectic Al3 Y-phase particles.The good combination of strength,plasticity,and electrical conductivity of the investigated Al-0.2 Y-0.2 Sc alloys make it a promising candidate for electrical conductors.The alloys exhibited a yield stress of 177-183 MPa,ultimate tensile stress of 199-202 MPa,elongation of 15.2-15.8%,and electrical conductivity of 60.8%-61.5% IACS.     

TEM study of Mg-Zn precipitates in Mg-Zn-Y alloys

The precipitates in Mg-Zn-Y alloys in the as-cast state with nominal atomic composition of Mg₉₆Zn₁Y₃, Mg₉₆Zn₂Y₂ and Mg₉₇Zn₁Y₂ were studied by means of TEM as well as XRD techniques. The results show that there is a phase separation of Zn on the nanometer scale in these alloys. Two kinds of nano-sized precipitates were found, namely MgZn and MgZn₂. TEM observation shows that MgZn precipitates are distributed in both the Mg matrix and in Mg₂₄Y₅ grains, which is the typical precipitate in Mg-Zn-Y alloys. There is an inherent crystallographic relationship between MgZn and Mg₂₄Y₅ precipitates: // , // . The size of MgZn₂ precipitates is much smaller than that of MgZn precipitates. They are distributed only in Mg₂₄Y₅ grains, not in the Mg matrix. It is suggested that the nano-sized precipitates, MgZn and MgZn₂, can improve the mechanical properties of the Mg-Zn-Y alloys studied.     

添加Sc、Zr和退火对Al-Si合金铸态力学性能的影响

使用OM、TEM、SEM、显微硬度和室温拉伸等手段研究了Sc和Zr的复合添加对Al-5.5Si合金铸态的组织和性能的影响,以及在不同温度退火后其性能的变化规律。结果表明,Sc、Zr的添加使Al-5.5Si合金的硬度提高了33%、抗拉强度提高了38%、屈服强度提高了52%、延伸率基本上不变。在Al-5.5Si合金中复合添加Sc、Zr使α-Al的平均晶粒尺寸从203 μm减小到130 μm,在α-Al基体中析出大量的Al₃(Sc_1-xZr_x)纳米粒子(10~15 nm),并使共晶Si内的层错或微孪晶的密度显著提高。退火温度对铸态合金的性能有较大的影响：在较低温度(低于160℃)退火时合金的硬度呈上升趋势,而在较高温度(高于280℃)退火时合金的硬度呈显著下降趋势。这些结果与二次析出的纳米Si相密切相关。     

往复挤压Mg-4Al-2Si合金中Mg2Si颗粒形貌与分布

使用往复挤压细化Mg-4Al-2Si (AS42)合金组织,利用OM,SEM和TEM研究Mg2 Si颗粒形貌和分布特征.结果表明,铸态AS42合金中Mg2Si颗粒呈共晶汉字状和初生块状.共晶Mg2 Si经2道次往复挤压后全部破碎,且分布均匀.经6道次挤压后初生Mg2 Si颗粒全部破碎,细小的Mg2 Si颗粒已基本球化....