挤压变形Mg一4Zn一xNd—O．5Zr合金的组织与性能

本文研究了分别加入0．5％、1．0％和1．5％Nd的挤压变形Mg一4Zn—O．5Zr合金经T5、T6热处理后的显微组织、拉伸性能和断裂行为,探讨了热处理对合金的组织与性能的影响。结果表明：晶粒尺寸按T6态、挤压态和T5态的顺序依次减小。三种舍金的拉伸性能均随Nd含量增加呈先升后降的趋势。T6处理使合金的拉伸性能降低,T5处理则有效地提高了合金的拉伸性能。     

Y含量对铸造Mg-Gd-Y-Nd-Zr合金组织与性能的影响

采用金相观察、硬度测试、扫描电镜观察、能谱分析、透射电镜观察、X射线衍射及室温拉伸等手段,研究了元素Y对铸造Mg-Gd-Y-Nd-Zr合金组织与性能的影响,结果表明:Y对该系合金的铸态组织无明显影响,在研究的成分范围内,不同成分合金的铸态组织均由α-Mg和非平衡共晶Mg5.05RE组成;经固溶处理后,非平衡共晶可溶入基体,但在晶界残留富稀土粒子,随着合金中Y含量降低,残留富稀土粒子的数量也降低;经T6处理后,合金中形成了大量的析出相β′,高Y含量合金中析出相的体积分数高于低Y含量合金,导致高Y含量合金T6态的硬度较高,但残留更多数量的富稀土粒子反而使高Y含量合金的拉伸强度和延伸率更低。经成分优化,较优的化学成分为Mg-5.5Gd-3.0Y-1.0Nd-1.0Zr,其铸造-T6态的抗拉强度为322 MPa,延伸率为4.0%,力学性能优于总稀土含量与之相当的商用WE54合金。     

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...     

室温大气环境下过时效状态3J21合金拉伸性能

在万能拉伸试验机上对室温大气环境下过时效态3J21合金的拉伸性能进行研究,并采用金相显微镜对过时效态金相组织及物相进行分析,采用TEN对固溶态、过时效态试样及拉伸断口附近形变的显微组织进行分析,采用扫描电镜（SEN）对拉伸断口进行观察。结果表明室温大气环境下,过时效态3J21合金的抗拉强度和屈服强度较低,延伸率较大;过时效态合金的拉伸断口为韧窝断口,断口上滑移线之间的距离较大。文中对室温大气环境下过时效态对3J21合金拉伸性能的影响进行了讨论。     

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。     

均匀化处理对2A12铝合金组织及性能的影响

为了获得力学性能优良的2A12铝合金并提高其合金化铣表面质量,综合采用差热分析(DSC)、扫描电镜(SEM)、透射电镜(TEM)、室温拉伸及表面粗糙度分析等测试方法,研究2A12铝合金均匀化对组织演变、析出行为、T6态合金化铣表面质量及力学性能的影响。结果表明:合金铸锭中存在的非平衡结晶相为S相、θ相及高熔点AlCuFeMn相,均匀化后晶界上残留第二相对合金化铣表面质量有重要影响;合金经495℃/12 h+505℃/18 h双级均匀化处理后,大量非平衡结晶相回溶基体,T6态组织中强化相S相呈片状析出密集分布,T相呈棒状弥散分布;获得最佳的合金均匀化制度为495℃/12 h+505℃/18 h,合金T6态化铣表面粗糙度为(1.18±0.06)μm,抗拉强度、屈服强度及延伸率分别为(469±3.5)MPa、(396±4.8) MPa和(11.8±0.1)%。     

Ti-6Al-4V合金的蠕变行为及影响因素

通过T6热处理、蠕变性能测试和SEM,TEM组织观察,研究了T6处理对Ti-6Al-4V合金组织结构与蠕变性能的影响.结果表明,锻造态Ti-6Al-4V合金在400℃/575MPa条件下具有较好的塑性和较低的蠕变寿命,并具有明显的温度敏感性.T6处理可明显提高合金的蠕变激活能和蠕变抗力,与锻造态合金相比,T6处理态合金在蠕变稳态期间具有较低的应变速率,并使蠕变寿命由66h提高到548h.锻造态合金的组织结构由a β相组成,T6处理后,合金的组织结构由a相与"网篮"相组成,其中"网篮"中大量针状β相沿不同取向析出是提高合金蠕变寿命的主要原因.蠕变期间,合金的蠕变机制是双取向的位错和位错在a相内发生柱面滑移和锥面滑移.     

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。     

Mg-Y-Nd-Zr-Zn 铸造镁合金组织与性能研究

目的研究Mg-Y-Nd-Zr-Zn镁合金的显微组织演变和力学性能。方法采用金相显微镜(OM)、扫描电镜(SEM)、能谱(EDS)以及电子万能实验机等,研究了Mg-Y-Nd-Zr-Zn镁合金铸态及T6态的组织和性能。结果 Mg-Y-Nd-Zr-Zn铸态合金组织由含Y的镁基固溶体、网状富稀土的共晶相和颗粒状的Zr单质组成;经525℃×10 h+200℃×16 h处理后,晶界网状第二相消失,细小的Mg-RE金属间化合物从基体中析出,弥散分布于晶界及晶内。结论 T6处理后,Mg-Y-Nd-Zr-Zn合金力学性能显著提高,抗拉强度、屈服强度和断裂伸长率分别为306 MPa,230 MPa和3.5%。     

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。     

Fatigue behavior of friction stir weld joints of Al–Zn–Mg alloy AA7039 developed using base metal in different temper condition

This paper presents the influence of base metal temper conditions (O, W and T6) on fatigue behavior of friction stir weld joints of Al–Zn–Mg alloy AA7039. Fatigue tests were performed at stress ratio of 0.1 and tensile to tensile stress in the range of 85–215 MPa to develop S–N curves. Fractured surfaces were investigated by SEM to determine the mode of fracture. On the basis of this study, friction stir welding of Al–Zn–Mg alloy AA7039 is recommended to be performed in W temper condition because of better tensile properties and superior fatigue strength.     

Effect of extrusion conditions on mechanical properties of Al-20Si-3Cu-1 Mg alloy prepared from rapidly solidified powder

A study on the optimization of extrusion conditions for a prospective Al-20Si-3Cu-1 Mg alloy prepared from rapidly solidified powder was carried out by evaluating tensile properties at room and elevated temperatures. It was found that extrusion conditions influence the asextruded microstructure and mechanical properties of the alloy to a certain extent. The relationship between the as-extruded mechanical properties and such extrusion variables as temperature, reduction ratio and die shape, can be described by using temperature-compensated strain rate, so that the as-extruded properties can be tailored in a certain range by adjusting this process parameter. In addition, the comparison between the as-extruded and as-T6 tempered tensile properties at elevated temperatures has opened the question as to the necessity of applying the heat treatment to the alloy — a normal practice subsequent to the extrusion. The experimental results suggest that for the material used at temperatures at and above 200 °C, the T6 temper treatment can be eliminated.     

含Ag的Al-Cu-Mg基合金的断续时效特征

采用维氏硬度、拉伸力学性能测试、扫描电镜和透射电子显微镜分析手段,研究了断续时效对含Ag的Al-Cu-Mg基合金的组织和性能的影响。结果表明:185℃高温欠时效Al-Cu-Mg-Ag合金在低温进行二次时效时,会发生二次析出现象,合金塑性显著提高。随着185℃欠时效时间的延长,合金二次时效初始硬度升高,峰值时间缩短,峰值硬度增量降低。二次时效温度为65℃时,合金中主要强化相为G.P.区和少量的Ω相,其峰值强度硬度低于T6态,提高二次时效温度至150℃,合金主要强化相为Ω相和少量的G.P.区,其峰值强度硬度略高于T6态。     

The effects of Mg amount on the microstructure and mechanical properties of Al–Si–Mg alloys

In this study, the effects of magnesium (Mg) addition to A356 aluminum alloy at different amounts on the microstructure and mechanical properties of this alloy were examined. For the experimental studies, three different alloys (0.43, 0.67 and 0.86 wt%) having various amounts of Mg were prepared through casting process in the form of plates. The plates were homogenized and cooled in the furnace. All the samples were treated with aging process (T6) and then tensile samples were prepared from the homogenized samples. The samples treated with T6 process were characterized by optical microscopy, laser confocal microscopy, Scanning Electron Microscope (SEM), Energy Dispersive Spectrometer (EDS) and X-Ray Diffraction (XRD) examinations as well as hardness measurements and tensile tests. The phases which were formed in the microstructures for different amounts of Mg were examined. It was observed that iron-rich intermetallic compounds were also formed in addition to the phases resulting from the aging process. Fe-rich intermetallic compounds, observed from the fracture surfaces, were found to reduce the tensile strength the alloy. The results also indicate that the tensile strength and hardness of the alloy increase with increasing Mg amount.     

镁稀土合金板材的热轧工艺与组织性能研究

对挤压态Mg-12Gd-3Y-0.4Zr合金板材在450℃下分别以10%,30%,50%和70%的道次压下量进行轧制,并对轧制板材进行时效处理以进一步提高其强度。本文研究了合金在轧制及时效态的组织及力学性能。试验结果表明,轧制过程可显著细化合金组织并有第二相析出,使力学性能得到提高。其中以50%压下量轧制的板材组织及力学性能最优,T5处理后其最高强度可达屈服396MPa,抗拉486MPa。     

一种新型高锌Al-Zn-Mg-Cu合金的热处理工艺

采用热顶直冷半连续铸造法制备了一种Zn元素含量达9.6%(质量分数)的Al-Zn-Mg-Cu系铝合金。利用金相显微镜、透射电镜进行微观组织观察,采用差热分析仪测试相转变温度。测试了硬度、拉伸性能并利用扫描电镜进行断口分析。表明:铸锭的铸态组织细小,晶间共晶相较少,共晶相的熔化温度为473.4℃。铸锭的均匀化工艺为465℃/24h,经均匀化处理后,晶界变为断续状,晶界相明显回溶。通过挤压法制备合金棒材,系统研究挤压棒材在不同温度下的单级和三级时效硬化曲线。表明在135℃/12h的单级时效制度下,合金挤压棒材的峰值硬度为197.7HBS,抗拉强度、屈服强度和伸长率分别为727.5,718.0MPa和9.3%;在120℃/24h+190℃/5min+135℃/3h的三级时效制度下,合金挤压棒材的峰值硬度为204.7HBS,抗拉强度、屈服强度和伸长率分别为764.0,749.0MPa和7.2%。     

Microstructure and mechanical properties of spray deposited and extruded 7000 series aluminium alloys

Abstract

The microstructure and mechanical properties of spray deposited 7000 series aluminium alloys were investigated. The 7000 type alloys were produced by the spray atomisation deposition method. These alloys were hot extruded and subsequently heat treated in the T6 and T7 temper conditions. Microstructural characterisation of the alloys was carried out by transmission electron microscopy (TEM). TEM studies revealed the presence of η′ and η(MgZn₂) hardening precipitates in both temper conditions. The mechanical properties were assessed through tensile and notched tensile tests using an Instron machine. It was observed that the 0.2% proof stress of these alloys after T7 temper decreased with increased elongation to fracture values.     

Sn对时效态ZM61镁合金高温力学性能的影响

利用金相显微镜(OM)、X射线衍射(XRD)、扫描电镜(SEM)和高温拉伸对时效态ZM61-xSn(x=0,6,8,10,质量分数/%,下同)合金的高温拉伸性能及断裂机制进行了研究。结果表明:ZM61-xSn(x=6,8,10)合金的物相由α-Mg,α-Mn,MgZn2,Mg2Sn相组成。添加Sn元素可有效细化ZM61合金组织,提高合金高温强度,但降低合金塑性。ZM61-xSn(x=6,8,10)合金在300℃下拉伸的抗拉强度分别为149,140,145MPa,较相同温度下拉伸的ZM61合金的抗拉强度分别提高了26%,17%,23%。ZM61-xSn(x=0,6,8,10)合金在300℃下拉伸的伸长率分别为39.95%,5.65%,7.01%和6.33%。拉伸温度对ZM61-xSn(x=6,8,10)合金的断裂机制产生显著影响。当拉伸温度低于220℃,合金为穿晶断裂;高于220℃时,合金变为沿晶断裂。     

Effect of heat treatment on the microstructure and mechanical properties of the spray-deposited Al–10.8Zn–2.8Mg–1.9Cu alloy

In this study, effect of various aging tempers (T6, T73 and RRA treatment) on the microstructure and mechanical properties of the spray-deposited Al–10.8Zn–2.8Mg–1.9Cu alloy was studied using high-resolution electron microscopy, selected area diffraction, and tensile tests. The results indicate that the two types of GP zones, GPI and GPII, are major precipitates for the alloy under T6 condition. No clear precipitation free zone was observed, and the grain boundary precipitates were continuous. Under two-step aging condition, the GP zones and η′ are major precipitates for the alloy, the discontinuous grain boundary precipitates are favorable to SCC resistance in over-aged condition, which reduces its strength 58 MPa (about 7%) compared to the peak-aged condition. After retrogression and re-aging treatment, the grain boundary precipitates are discontinuous, which is closed to that resulting from T73 temper. RRA treatment decreased ultimate tensile strength 25 MPa (about 3%) in values compared with the alloy at T6 condition.     

Development of mechanical properties during secondary aging in aluminium alloys

Abstract

Earlier work has shown that, if the artificial aging of aluminium alloys is interrupted by a dwell period at lower temperature, higher values of tensile properties and fracture toughness may be achieved than are possible with single stage T6 tempers. A second interrupted aging cycle has now been developed that involves underaging at the elevated temperature, quenching, and then allowing secondary precipitation to occur at, or just above, room temperature. Designated a T6I4 (I=interrupted) temper by the authors, this simpler aging cycle may reduce heat treatment costs. Tests on some 30 cast and wrought alloys have resulted in tensile properties close to those for a T6 temper, with higher values of fracture toughness being recorded for some cases. Such an aging treatment can be incorporated into a paint bake cycle to simplify the heat treatment of coated automotive components.