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。     

元素固溶与析出对镁合金耐蚀性影响的研究进展

合金元素的固溶与析出改变了镁基体相电位和第二相的种类,从而显著影响镁合金的微电偶腐蚀行为.本文综述了元素固溶与析出对镁合金耐蚀性影响的研究现状,总结了典型合金元素在镁合金中固溶析出的典型第二相,重点阐述了基于热力学和动力学分析常见镁合金系中的固溶和析出行为对镁合金的腐蚀行为的影响,指出了良好的镁合金候选材料应具备的条件,提出了提高镁合金本征耐蚀性的设计方法,未来研究重点应通过调控镁合金中合金元素的种类和数量来降低镁合金腐蚀速率,扩大合金应用范围.     

Mg-Gd-Y-Zr 活塞微观组织及力学性能研究

目的研究Mg-Gd-Y-Zr镁合金活塞本体的微观组织和力学性能。方法采用金属型重力铸造工艺制备镁合金活塞,利用光学显微镜和扫描电镜分析了铸态、固溶态(T4)和固溶时效态(T6)活塞本体的显微组织,利用岛津材料试验机和硬度计测试活塞本体的力学性能。结果铸态Mg-Gd-Y-Zr镁合金活塞本体组织中大量的第二相分布于晶界处,T4处理后大部分固溶到基体中,T6处理后晶粒内部出现麻点状和细条状的析出相。活塞裙部和顶部经T6处理后的抗拉强度随着拉伸温度的升高而逐渐降低,在300℃拉伸时活塞裙部抗拉强度达到226.38 MPa;活塞裙部和顶部的伸长率随着拉伸温度的升高而增加,在350℃拉伸时活塞裙部伸长率达到23.65%。结论镁合金活塞裙部的室温和高温抗拉强度好于活塞顶部,裙部尺寸较均匀。     

时效态Mg-Gd-Y-Nd合金的组织结构及耐腐蚀性能

镁合金中加入Gd、Y、Nd等元素能提高其耐蚀性能,但目前对同时加入3种元素的情况研究较少。采用熔炼法制备了Mg-10Gd-3Y-Nd合金,并对其进行时效处理。利用金相显微镜、扫描电镜、X射线衍射仪等研究了时效态Mg-10Gd-3Y-Nd合金的微观组织及物相。通过静态失重法研究了时效态合金在不同浓度NaCl溶液中的耐腐蚀性能。结果表明:时效态合金主要由基体α-Mg和晶间共晶相(Mg_5Gd、Mg_(24)Y_5)组成,Gd能够良好地固溶于镁合金基体中;随着NaCl溶液浓度的增加,时效态合金的腐蚀速率增加,腐蚀深坑严重,颗粒状腐蚀物逐渐转为粉状;第二相颗粒的存在能阻止腐蚀过程向更深的晶粒区域发展,降低了腐蚀程度,提高了合金的耐腐蚀性。     

热变形方式对2D70耐热铝合金组织与性能的影响

分别采用常规变形方式(直接挤压)、强变形方式(3次多方锻造与挤压变形相结合)制备了大规格2D70耐热铝合金棒材,利用金相显微镜、透射电镜、力学性能测试、电导率测试等手段对比分析了两种工艺所获得棒材的变形态、固溶态显微组织特征以及195℃人工时效强化特性差异。结果表明,与传统直接挤压方式相比,采用强变形工艺所获得的基体组织相对均匀,合金中各类第二相破碎严重、分布合理;经强变形破碎的Al2CuMg、Al2Cu等可溶第二相可在固溶处理过程中充分回溶以提高时效强化潜力,同时,Al9FeNi、Al7Cu4Ni等难溶第二相的尺寸、形态与分布通过强变形得以合理调控,使得合金棒材在195℃人工时效的过时效阶段具有更优越的抗过时效能力,合金热稳定性较好。     

固溶处理对7A55铝合金局部腐蚀性能的影响

采用电化学测试、浸泡实验、金相显微镜、扫描电镜、透射电镜等实验手段研究固溶处理对7A55铝合金局部腐蚀性能的影响。结果表明:轧板中大量的第二相使轧板发生严重的腐蚀,整个表面被剥落下来。单级固溶的再结晶程度较低,亚晶组织细小,但合金残留第二相较多,耐蚀性能差。低温回复+高温固溶处理(450℃/1h+480℃/30min)可以将粗大第二相大部分溶解,且获得最少的再结晶分数和细小亚晶组织。实验结果表明,450℃/1h+480℃/30min固溶处理具有最佳的耐局部腐蚀性能。     

铸造Al-Zn-Mg-Cu-Zr-Sc合金热处理析出相转变及其对力学性能的影响

目的 为满足高速列车关键部件的轻量化需求,开发高性能铸造铝合金。方法 熔炼铸造了低锌、低镁且含微量钪的Al-5.78Zn-1.63Mg-1.75Cu-0.17Zr-0.22Sc(质量分数)合金,对合金实施了双级均匀化处理及“固溶+时效”(T6)工艺,结合光镜(OM)、X射线衍射仪(XRD)、扫描电镜(SEM)、能谱仪(EDS)及透射电镜(TEM)多种分析测试手段,对比研究合金在铸态、均匀化态及T6处理态下的微观组织特征,重点关注了析出相的演变,并通过室温拉伸性能实验测试合金的力学性能。结果 铸态合金中的析出相以粗大的Mg(Zn,Cu,Al)₂相为主,且分布于晶界或枝晶界,在室温拉伸过程中粗大的Mg(Zn,Cu,Al)₂相割裂基体,造成合金在弹性变形阶段的脆断,基本无伸长率;双级均匀化处理后,晶界及枝晶间的第二相明显减少,晶内析出了大量的针状相Mg(Zn,Cu,Al)₂,而T6处理后,晶内针状相基本消失,时效过程中析出以η’-MgZn₂相为主的高密度弥散分布纳米析出相,其平均尺寸为(9.2±0.9)n...     

铸造Mg-3Zn-0.5Cu-0.6Zr镁合金的时效析出行为研究

利用金相显微镜、显微硬度计、X射线衍射仪、扫描和透射电镜研究了铸造Mg-3Zn-0.5Cu-0.6Zr镁合金铸态和固溶时效后的显微组织,初步确定了时效Mg-3Zn-0.5Cu-0.6Zr镁合金中主要合金相的种类和形态.合金铸态组织主要由初晶Mg基体和(Mg+Mg2Cu,CuMgZn)共晶组成.固溶后,晶界处大部分非平衡共晶组织溶解;180℃/20h时效后达到合金时效硬度峰值,此时晶内析出相主要有三类:(1)轴线垂直于(0001)Mg,板条状或棱柱状β2’-MgZn2,长度50nm～200nm,该相是合金的主要时效硬化相;(2)较粗大的、其轴线仍与基面垂直的六棱柱状β2’-MgZn2;(3)轴线平行于(0001)Mg,板条状或针状β-MgZn,长度50nm～150nm.     

Cu-7Ni-0.75Al-1.5Cr成分设计及热处理组织分析

通过对铜合金Cu-7Ni-0.75Al-1.5Cr合金中主要化学元素的分析,对合金进行了成分的设计。研究了铜合金冷轧态、固溶处理、变形＋时效、固溶＋时效的金相组织。实验得出该铜合金的最佳固溶处理温度及固溶态形貌以及时效强化析出相的形貌。     

固溶工艺对Ti12LC合金组织性能的影响

Ti12LC合金是西北有色金属研究院研制的一种低成本钛合金,用于取代TC11合金进行推广应用。本文对420mm Ti12LC合金铸锭进行常规锻造,得到等轴组织的170mm Ti12LC合金棒材。采用单重固溶+时效、双重固溶+时效两种不同的工艺对Ti12LC合金进行热处理,分析不同固溶工艺对Ti12LC合金显微组织及室温拉伸、室温冲击性能的影响。研究表明,在相同的固溶冷却速率下,增加单重固溶温度,初生等轴α相含量减少,合金强度增加、塑性减小、冲击韧性减小。单重固溶+时效热处理后合金冲击韧性低、强韧性匹配差。与单重低温固溶+时效相比,合金经高温预固溶慢冷+低温固溶处理后,初生α相尺寸及相含量变化不明显,但可以获得更大尺寸的次生α相,合金的塑性稍有降低、强度增加、冲击韧性改善明显,综合力学性能匹配良好。     

Dealloying corrosion of anodic and nanometric Mg41Nd5 in solid solution-treated Mg-3Nd-1Li-0.2Zn alloy

The microstructure and chemical compositions of the solid solution-treated Mg-3Nd-1Li-0.2Zn alloy were characterized using optical microscope,scanning electron microscope(SEM),transmission electron microscope(TEM),electron probe micro-analyzer(EPMA)and X-ray photoelectron spectroscopy(XPS).The corrosion behaviour of the alloy was investigated via electrochemical polarization,electrochemical impedance spectroscopy(EIS),hydrogen evolution test and scanning Kelvin probe(SKP).The results showed that the microstructure of the as-extruded Mg-3Nd-1Li-0.2Zn alloy contained α-Mg matrix and nanometric second phase Mg41 Nd5.The grain size of the alloy increased significantly with the increase in the heat-treatment duration,whereas the volume fraction of the second phase decreased after the solid solution treatment.The surface film was composed of oxides(Nd2O3,MgO,Li2O and ZnO)and carbonates(MgCO3 and Li2CO3),in addition to Nd.The as-extruded alloy exhibited the best corrosion resistance after an initial soaking of 10 min,whereas the alloy with 4h-solution-treatment possessed the lowest corrosion rate after a longer immersion(1 h).This can be attributed to the formation of Nd-containing oxide film on the alloys and a dense corrosion product layer.The dealloying corrosion of the second phase was related to the anodic Mg41Nd5 with a more negative Volta potential relative to α-Mg phase.The preferential corrosion of Mg41Nd5 is proven by in-situ observation and SEM.The solid solution treatment of Mg-3Nd-1Li-0.2Zn alloy led to a shift in corrosion type from pitting corrosion to uniform corrosion under long-term exposure.     

Microstructure,mechanical and corrosion properties of Mg–Nd–Zn–Sr–Zr alloy as a biodegradable material

Abstract

The Mg–2·5Nd–0·3Zn–0·1Sr–0·4Zr (wt-%) alloy was prepared by gravity casting. Solution treatment and extrusion were conducted. The microstructure, mechanical properties, and corrosion behaviour of the alloy under as cast, T4-treated, and as extruded conditions were evaluated using scanning electron microscope, tensile test, microhardometre, immersion test, and electrochemical test. The results show that the as extruded alloy exhibits the highest ultimate tensile strength (231 MPa), elongation (36·6%), and microhardness (57·8 HV). The as cast alloy shows the best corrosion resistance because the relative continuously distributed eutectic phase with noble corrosion potential acts as a corrosion barrier. The as extruded Mg–Nd–Zn–Sr–Zr alloy with high ductility and good corrosion resistance is desirable for preparing biodegradable implants.     

Pitting corrosion of a Rare Earth Mg alloy GW93

Pitting corrosion of magnesium(Mg) alloys is greatly associated with their microstructure, especially second phases. The second phases in traditional Mg alloys such as AZ91 are electrochemically nobler than Mg matrix, while the second phases in Rare earth(RE) Mg alloy GW93 are more active than Mg matrix. As a result, the pitting corrosion mechanism of Mg alloy GW93 is different from the traditional ones. This paper aims to clarify the pitting corrosion mechanism of Mg alloy GW93 through the studies of Volta potential by Scanning Kelvin Probe Force Microscopy(SKPFM), corrosion morphology by Scanning Electron Microscope(SEM), and corrosion resistance by electrochemical tests. Results reveal that the pitting corrosion of GW93 includes three stages, first, dissolution of the second phases, followed by corrosion of Mg matrix adjacent to the dissolved second phases, and finally, propagation of corrosion pits along the depth direction of the dissolved second phases. Anodic second phases and enrichment of Clin the thick corrosion product films dominate the propagation of pitting corrosion.     

Influence of Heat Treatments on In Vitro Degradation Behavior of Mg‐6Zn Alloy Studied by Electrochemical Measurements

The influence of heat treatment on the in vitro degradation of Mg‐6Zn alloy is studied by electrochemical measurements. After solid‐solution treatment, the microstructure of the Mg‐6Zn becomes more homogeneous, along with an elevated charge‐transfer resistance in SBF and a reduced corrosion current density. After ageing treatment, the discrete intermetallic γ‐MgZn phase enhances the cathodic hydrogen evolution and impairs the corrosion resistance of the alloy. Galvanic cells are expected on ageing, but the ageing process makes the microstructure of the alloy homogeneous. Heat treatment alters the in vitro degradation behavior of Mg‐6Zn alloy and is applicable in adjusting the biodegradation rate.     

Improving the corrosion resistance of Mg–4.0Zn–0.2Ca alloy by micro-arc oxidation

In this paper, corrosion resistance of the Mg–4.0Zn–0.2Ca alloy was modified by micro-arc oxidation (MAO) process. The microstructure and phase constituents of MAO layer were characterized by SEM, XRD and X-ray photoelectron spectroscopy (XPS). The corrosion resistance of MAO treated Mg–4.0Zn–0.2Ca alloy in the simulated body fluid were characterized by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The microstructure results indicated that a kind of ceramic film was composed by MgO and MgF₂ was formed on the surface of Mg–4.0Zn–0.2Ca alloy after MAO treatment. The electrochemical test reveals that the corrosion resistance of MAO treated samples increase 1 order of magnitude. The mechanical intensity test showed that the MAO treated samples has suitable mechanical properties.     

镁合金激光重熔后微弧氧化膜的微观组织和耐蚀性能

为了改善WE43镁合金的耐蚀性能,采用激光重熔(LSM)和微弧氧化(MAO)复合工艺对其表面进行了改性。通过扫描电子显微镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)研究了WE43镁合金及其激光重熔层、微弧氧化膜层和激光重熔-微弧氧化膜层的微观组织、表面形貌和物相;通过GAMARY-Reference 600电化学工作站研究了其腐蚀行为,重点研究了镁合金激光重熔后微弧氧化膜层的微观组织、成分和耐蚀性能。结果表明:激光重熔使WE43镁合金晶粒细化、网状的β-Mg41Nd5相均匀分布和表面稀土元素Y及Nd增加,有效地改善了其耐蚀性能;微弧氧化膜和激光重熔后的微弧氧化膜层都可以显著提高WE43镁合金的耐蚀性能,但后者优于前者。     

Al-Zn-Mg-Cu系超高强度铝合金的研究进展

Al-Zn-Mg-Cu系超高强度铝合金具有低密度、高比强度、高韧性和良好的抗腐蚀性能的特点,广泛应用于航空航天、交通运输和兵器领域。本文主要介绍近年来国内外Al-Zn-Mg-Cu系超高强度铝合金的最新研究进展。超高强度铝合金基体上分布着纳米级的晶内时效析出相、亚微米级的高温析出相、微米级的结晶析出相和晶界析出相,这些相的形态、数量、尺寸和分布对合金的综合力学性能和抗腐蚀性能有直接的影响;主元素成分含量对超高强度铝合金综合力学性能有影响,合金的综合力学性能随Zn/Mg和Cu/Mg比值的变化而变化;微量元素能够提高超高强度铝合金的综合力学性能。微量元素对铝合金的影响主要体现在提高沉淀相的过饱和度,改变沉淀析出过程,促进或抑制沉淀相的析出和促进新相的沉淀析出。新制备技术能够显著细化晶粒、抑制偏析、析出相均匀分布和提高各种元素的过饱和度,从而改善超高强度铝合金的综合力学性能。强化固溶处理能够提高时效析出程度,从而提高铝合金的力学性能。三级时效处理后的超高强度铝合金具有峰值时效T6态的强度和优异的抗腐蚀性能。     

快速凝固/粉末冶金高硅铝合金微观组织及拉伸性能

采用快速凝固／粉末冶金法制备Al-17Si-6Fe-4.5Cu-0.5Mg合金,并进行T6处理。利用现代测试手段对挤压态及T6处理态合金微观组织及拉伸性能进行研究。结果表明：采用这种工艺可使合金组织中第二相得到显著细化,经T6处理后第二相有粗化趋势,同时也有新相沉淀析出;合金拉伸性能主要表现在高温、低塑性及良好耐热性。     

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.