Mg-6Gd-3Y-2Zn-0.5Zr镁合金的组织和性能

设计了新型Mg-6Gd-3Y-2Zn-0.5Zr镁合金,并用光学显微镜、扫描电镜及拉伸试验机对合金铸态、均匀化态及挤压态的显微组织特征和力学性能进行了研究。结果表明,铸态Mg-6Gd-3Y-2Zn-0.5Zr合金组织主要由α-Mg基体和沿晶界分布的块状长周期堆垛有序结构相组成,均匀化处理(450℃×16h)促使细小层片状的长周期堆垛有序结构相由晶界向晶内生长。挤压态Mg-6Gd-3Y-2Zn-0.5Zr合金在200℃下时效处理,无明显时效硬化现象,但挤压态合金具有优良的强韧性能,室温抗拉强度、屈服强度和伸长率分别为335MPa、276MPa和17%。     

Sm对Mg-10Gd-0.5Zr合金组织及力学性能的影响

采用熔炼铸造法制备了添加1%～5%Sm(质量分数)的Mg-10Gd-0.5Zr合金,通过拉伸性能测试、扫描电镜、X射线衍射分析研究了Sm对合金显微组织和力学性能的影响。结果表明:Sm的加入形成了Mg41Sm5相,并促进了Mg_5Gd相析出。固溶时效处理后,晶界处粗大共晶组织溶解,析出相弥散分布,3%Sm的合金晶粒较细小,5%Sm的合金中出现短棒状Mg_5Gd相。在相同实验温度下,随着Sm含量的增加,合金的强度先升高后降低,3%Sm的合金抗拉强度最大。对于同一种合金,随着拉伸温度的升高抗拉强度先升高后降低,加入0%～1%Sm的合金抗拉强度峰值出现在200℃,加入3%～5%Sm的合金抗拉强度峰值出现在250℃。抗拉强度具有明显的反常温度效应,而且Sm的加入强化了这种反常温度效应并使强度峰值出现的温度升高。     

Hot Deformation and Subsequent Annealing on the Microstructure and Hardness of an Al0.3CoCrFeNi High-entropy Alloy

The influence of simple thermomechanical processing such as hot deformation and heat treatment on the microstructure and hardness of an Al0.3CoCrFeNi high-entropy alloy has been investigated.Results show that the relatively high deformation temperature can induce discontinuous dynamic recrystallization with fine grains initially nucleating at the elongated grain boundaries.The transition from partial recrystallization to fully recrystallization,as well as the precipitation behavior after annealing,has been described in detail.Both bcc precipitation and completely recrystallized grains can be observed after annealing at 1000 ℃.Based on detailed microstructure analysis,the decrease in hardness value is shown to be related to both dynamic recrystallization and dynamic recovery which lead to softening.     

热处理对压铸Mg-8Gd-3Y-0.5Zr合金组织性能的影响

采用气体保护法制备Mg-8Gd-3Y-0.5Zr(GW83K)合金,并冷模压铸成拉伸试样。通过光学显微镜、扫描电镜观察及力学性能测试等分析合金压铸态和不同热处理状态下的显微组织及力学性能。结果表明:冷模压铸GW83K合金经热处理后,其力学性能较压铸态均有所提高,尤其是经低温短时固溶处理(T4)后的合金,其晶粒度变化不大,组织比较均匀,片层状的共晶体消失,第二相以不连续的棒状或粒状分布于晶界处。GW83K-T4合金的室温拉伸性能可达到σb=261.7MPa,σs=240.8MPa,δ5=6.0%,比压铸态合金分别提高了21%,28.4%和30.4%,且该合金具有较好高温力学性能。     

Nd对Mg-13Gd-0.5Zr合金组织和力学性能的影响

采用X射线衍射仪、光学显微镜、扫描电镜、能谱仪和电子拉伸试验机等设备研究了Nd对Mg-13Gd-0.5Zr合金组织和力学性能的影响,结合错配度理论、位错密度的变化规律讨论了合金晶粒细化的机理,并从细晶强化和析出强化等方面阐述了合金强化机制。研究发现Mg-13Gd-0.5Zr合金的组成相主要有α-Mg、Mg₅Gd,Nd的加入在合金中形成了新相Mg₄₁Nd₅,并细化了合金晶粒。Nd的加入显著提高了Mg-13Gd-0.5Zr合金的室温和高温力学性能,当Nd的添加量为2%时,合金在室温和高温下的力学性能达到最大值279(室温)、319 MPa(250 ℃),合金力学性能的提高主要归因于Mg₅Gd和Mg₄₁Nd₅相的析出强化和细晶强化的双重效果。Mg-13Gd-2Nd-0.5Zr合金在不同温度下的断裂方式主要以脆性断裂为主,随着拉伸温度的升高并由脆性断裂向韧性断裂转变。     

Mg-2.6Sm-1.3Gd-0.6Zn-0.5Zr镁合金显微组织和力学性能研究

研究了不同固溶处理工艺对Mg-2.6Sm-1.3Gd-0.6Zn-0.5Zr合金显微组织和力学性能的影响。合金的铸态显微组织主要由α-Mg和(Mg,Zn)3(Sm,Gd)1共晶相组成。510℃,4 h为最佳固溶处理条件,晶界附近的共晶相几乎全部溶于镁基体中,合金固溶态的室温抗拉强度为246 MPa,延伸率为11.3%。合金200℃时效析出序列为Mgssss→β’’(D019)→β’(bct)→β(fcc),峰时效态合金的屈服强度和抗拉强度达到185 MPa和282 MPa,延伸率为6.1%。     

退火工艺对AZ31镁合金组织与性能的影响

研究了热处理工艺对AZ31镁合金轧制板材的显微组织和力学性能的影响。试验表明，AZ31镁合金轧制板材在退火过程中发生了静态再结晶现象，200℃时可以观察到再结晶现象，再结晶温度为200～250℃。分析了退火温度和退火时间对合金显微组织、晶粒尺寸、硬度以及力学性能的影响规律。     

Effect of Solution Treatment on Microstructure and Corrosion Properties of Mg–4Gd–1Y–1Zn–0.5Ca–1Zr Alloy

The as-cast multi-element Mg–4Gd–1Y–1Zn–0.5Ca–1Zr alloy with low rare earth additions was prepared, and the solution treatment was applied at different temperatures. The microstructural evolution of the alloy was characterized by optical microscopy and scanning electron microscopy, and corrosion properties of the alloy in 3.5% NaCl solution were evaluated by immersion and electrochemical tests. The results indicate that the as-cast alloy is composed of the a-Mg matrix,lamellar long-period stacking-ordered(LPSO) structure and eutectic phase. The LPSO structure exists with more volume fraction in the alloy solution-treated at 440 °C, but disappears with the increase in the solution temperature. For all the solution-treated alloys, the precipitated phases are detected. The corrosion rates of the alloys decrease first and then increase slightly with the increase in the solution temperature, and the corrosion resistance of the solution-treated alloys is more than four times as good as that of the as-cast alloy. In addition, the alloy solution-treated at 480 °C for 6 h shows the best corrosion property.     

砂型铸造Mg-9Gd-4Y-0.5Zr合金的微观组织和力学性能

通过金相观察(OM)、扫描电镜(SEM)、能谱分析(EDS)、显微维氏硬度测试与拉伸测试研究了砂型铸造Mg-9Gd-4Y-0.5Zr合金的微观组织和力学性能。结果表明:铸态GW94合金主要由等轴晶琢-Mg固溶体、晶界处的共晶相Mg24(Gd,Y)_5以及少量的方块相Mg_5(Gd,Y)组成,优化后的固溶处理工艺为525℃伊6 h。固溶后的组织主要由琢-Mg过饱和固溶体、铸态残留相Mg_5(Gd,Y)以及固溶过程形成的方块相组成。GW94合金具有极高的时效硬化响应能力,250℃时效18 h后即达到峰值硬度(HV122)。室温拉伸时,峰值时效态合金的抗拉强度和屈服强度分别为300MPa和247 MPa,而伸长率仅为0.9%。250℃以内拉伸时,抗拉强度均高于300 MPa,表现出极佳的耐热性能,而且出现了抗拉强度随温度升高而升高的反常力学行为,这可能是由于茁忆相与位错相互作用所致。峰值时效态合金断裂机制由室温的穿晶断裂为主转变为高温的沿晶断裂。     

Mg-12Gd-2Y-1.5Sm-0.5Zr合金显微组织和力学性能

研究了合金元素对Mg-12Gd-2Y-1.5Sm-0.5Zr合金显微组织和力学性能的影响.结果表明,该合金晶粒组织细小,少量Y、Sm和大量Gd固溶在镁基体里,同时有少量MgGd3、Mg24Y5和Mg41Sm5相析出;合金在室温、200、250℃下的抗拉强度分别为258、304、330 MPa;断裂为脆性断裂,与合金的低伸长率相对应.     

异步轧制AZ31镁合金板材在退火处理中的组织性能演变

研究了异步轧制AZ31镁合金板材经200～350 ℃退火30～120 min后的组织性能演化.在试验条件下,AZ31镁合金板材在200 ℃退火时,随保温时间的延长,组织的均匀程度和晶粒尺寸没有明显变化;在300 ℃退火30 min,基本完成再结晶过程,获得均匀细小的等轴晶,保温时间增加到60 min时,部分再结晶晶粒长大;在350 ℃退火30 min和60 min,均在完成再结晶的同时晶粒长大;300 ℃退火30 min后AZ31镁合金板材的综合性能较好,室温抗拉强度为315 MPa,伸长率为33.0%.     

挤压铸造Mg-9Gd-1Y-0.5Zr活塞的组织与性能

挤压铸造了Mg-9Gd-1Y-0.5Zr(GW91)活塞,研究了固溶时效态(T6)活塞顶部及裙部的力学性能,以及在200～300℃的蠕变性能.结果表明,活塞经过固溶时效处理后,晶粒内部析出相均匀析出,顶部和裙部平均晶粒尺寸分别为140、80 μm; T6态活塞的抗拉强度随温度增加而降低,当温度为300℃时,活塞顶部及裙部抗拉强度分别达到210、223MPa;T6态活塞稳态蠕变速率随温度及应力增加而增大,在300℃、50 MPa蠕变条件下,活塞顶部及裙部稳态蠕变速率分别为7.81×10-8 s-1、1.45×10-7 s-1,蠕变100 h后蠕变量分别为2.8％、3.0％,优于现阶段商用活塞材料Al-Si合金的高温抗拉强度和抗蠕变性能.     

Mg-9Li-5Gd-1Zr合金的组织转变及力学性能

采用常规熔炼工艺制备Mg-9Li-5Gd-1Zr合金,考察了合金元素、均匀化热处理及ECAP挤压对Mg-9Li双相合金组织转变与力学性能的影响.结果表明,合金元素Gd和Zr能显著细化Mg-9Li双相合金中的α-Mg相,使其成为细小的条状,并均匀分布于基体中;与形成的具有取向分布的针状Mg3Gd对铸态合金起主要强化作用.均匀化热处理使β-Li基体晶粒明显长大;β-Li基体内的针状Mg3Gd相发生部分溶解、数量急剧减少;条状α-Mg相沿晶界偏聚长大,形成块状;合金强度较铸态略有下降,伸长率显著提高.ECAP一道次挤压在细化基体组织,改善组织均匀性的同时,导致均匀化处理合金中条状α-Mg相和针状Mg3Gd相破碎细化,诱导回溶的Mg3Gd相沿流变方向再次析出,合金较均匀化处理的强度、塑性均有所下降.     

均匀化退火工艺对铸态Mg-9Gd-3Y-0.5Zr镁合金组织及性能的影响

采用光学显微镜、X射线衍射等研究了均匀化退火工艺对Mg-9Gd-3Y-0.5Zr镁合金组织和性能的影响.结果表明,均匀化退火能有效消除枝晶偏析,改善材料的组织和力学性能;退火温度对均匀化起主要作用.确定了480℃×8h均匀化退火工艺为铸态Mg-9Gd-3Y-0.5Zr镁合金的最佳处理工艺.     

新型铸造镁合金Mg-3.0Nd-1.5Gd-0.25Zn-0.5Zr的组织和力学性能

研究了新型铸造镁合金Mg-3.0Nd-1.5Gd-0.25Zn-0.45Zr的组织和力学性能。研究表明,试验合金的铸态组织为近等轴晶,主要由α-Mg基体和晶界处的(α-Mg+Mg12Nd)共晶组成。试验确定了固溶试验合金的较优时效处理工艺。试验合金经T6热处理后,室温屈服强度较ZM6合金显著提高。同时,试验合金的高温瞬时抗拉强度、屈服强度以及抗蠕变性能均显著优于ZM6合金。     

Texture Evolution and Dynamic Recrystallization of Zr-1Sn-0.3Nb-0.3Fe-0.1Cr Alloy During Hot Rolling

In the present work,the sheets of Zr-1Sn-0.3Nb-0.3Fe-0.1Cr alloy were hot rolled with different reductions(10%,30%,50%,and 60%) at 1023 K and 1073 K.The micro structure evolutions including grain micro structure,texture,and dislocation were investigated,using electron backscattering diffraction and transmission electron microscope.The results showed that dislocation slip,twinning,and dynamic recrystallization(DRX) were the main deformation mechanisms.DRX was found to be promoted by larger reduction and higher rolling temperature.The predominant texture formed during hot rolling was basal 0001//ND,whose intensity reached peak value after 30% reduction hot rolling.While the intensity of DRX texture 10-10//ND and1-210//ND increased with increasing reduction and temperature.This study provided an effective way to tailor the texture and microstructure of the alloy,for optimizing process parameters.     

Mg-15Gd-0.6Zr合金的组织与力学性能

通过在Mg-Gd二元合金中添加少量的Zr后制备一种新型的Mg-15Gd-0．6Zr合金，并对合金的微观组织、时效特性和不同温度下的力学性能及拉伸断裂方式进行研究。合金在非平衡凝固过程中容易形成MgxGd（x=2，3，5）相，但用热处理的方法几乎不可能消除。在合金的Cast-T5、Cast-T6、Ext-T5和Ext—T6的4种时效状态中，Ext—T5态达到峰值硬度的时间最短，峰值硬度值最高；而Cast-T5态的则相反。合金具有较高的耐热强度和延伸率，其在不同温度下的抗拉强度与WE54的相当，而延伸率明显优于WE54及其它耐热镁合金的。合金在25℃时的断裂方式以准解理断裂为主，而250℃时的断裂方式以微孔聚集型断裂为主，300℃和350℃时的断裂方式以典型的微孔聚集型断裂为主。     

Microstructure and Mechanical Property of Hot-Rolled Mg-2Ag Alloy Prepared with Multi-pass Rolling

A conventional multi-pass rolling is designed to form different microstructures in a Mg-2Ag alloy. The relationship between microstructure and mechanical property is investigated. The result shows that twin-induced nucleation plays a prominent role for the dynamic recrystallization (DRX) behavior of the rolled Mg-2Ag alloys. The DRXed grains distributed around elongated grains have random orientations but gradually turn to the concentrated orientation with strong basal texture when the rolling pass increases. The yield strength and ultimate tensile strength of rolled Mg-2Ag alloy gradually increase with increasing rolling pass. The elongation of rolled sample is gradually improved when the rolling pass increases from one to three, while a significant drop of elongation shows in the four-pass rolling sample. The strong basal texture, refined grains, high-density dislocations, and Ag segregation along grain boundaries are suggested to play a prominent role for enhancing the strength of Mg-Ag alloys, while the low-density dislocations, homogeneously fine-grained microstructure, and weak texture are critical for improving the ductility.     

高应变速率多向锻造Mg-8Gd-1Er-0.5Zr合金的微观组织、织构及力学性能

以固溶态Mg-8Gd-1Er-0.5Zr(质量分数,％)合金为对象,研究了在高应变速率多向锻造过程中合金微观组织及织构的演变规律,并探讨了高应变速率多向锻造对合金力学性能的影响机制.结果表明,变形初期,合金晶粒内部的大部分{101ˉ2}拉伸孪晶被激发,随着累积应变(ΣΔε)的增加,孪晶面积分数降低,再结晶面积分数增高,再结晶机制以连续动态再结晶为主,同时伴有不连续动态再结晶和孪生诱导再结晶.合金晶粒细化分为2个阶段:当ΣΔε<1.32时,为孪晶破碎机制,晶粒尺寸由初始态的33.0μm细化至13.1μm;当ΣΔε≥1.32时,为动态再结晶细化机制,晶粒尺寸进一步细化至4.2μm.合金织构随ΣΔε增加由基面织构转变为双峰织构,且织构强度增加.ΣΔε=0.66时,多向锻造Mg-8Gd-1Er-0.5Zr合金的抗拉强度、屈服强度和延伸率分别达到295 MPa、252 MPa和13.8％,比固溶态分别提高了80％、157％和13.1％.     

Effect of Hydrostatic Pressure on LPSO Kinking and Microstructure Evolution of Mg-11Gd-4Y-2Zn-O.5Zr Alloy

Two different kinds of hot compressions,namely normal-compression and can-compression,were performed on the Mg-11Gd-4Y-2Zn-0.5Zr alloy,featured with long period stacking ordered (LPSO) phase.The kinking behavior of LPSO phase and microstructure evolution was investigated to clarify the effect of levels of imposed hydrostatic pressure.The results suggest that the LPSO phases including both the intragranular 14H-LPSO phase and intergranular 18R-LPSO phase suffer severe kinking behavior under higher hydrostatic pressure induced by can-compression,which is firstly characterized with more kinking times and smaller relative kinking width.The main reason for such enhanced LPSO kinking during cancompression may be mainly ascribed to the higher dislocation density under a higher level of hydrostatic pressure.Meanwhile,a competitive relationship between the kink behaviors of intergranular 18R-LPSO phase and intragranular 14H-LPSO phase was observed.That is,the intergranular 18R-LPSO phase only kinks obviously on the condition that the surrounded intragranular 14H-LPSO phase scarcely kinks.In contrast to the distinctive kinking of LPSO phase,the dynamic recrystallization (DRX) mechanism shows less dependence on the hydrostatic pressure.Resultantly,similar DRX fractions and crystallographic texture were attained for two compression processes owing to the similar operation of deformation mode.