Mg-6Zn-1Y-Zr镁合金的组织与性能研究

Mg-6Zn-1Y-Zr镁合金在热锻或热挤压过程中发生了动态再结晶.合金组织细化,但不均匀,平均晶粒尺寸约10 μm.挤压态材料经350℃×30 min再结晶退火转变为等轴细晶组织,平均晶粒尺寸已达到5μm左右.合金在变形处理后有新的第二相析出,且合金的力学性能有很大提高.其中锻态Mg-6Zn-1Y-Zr合金的σb达到265 MPa,σ0.2达155 MPa,挤压态合金的σb达到330 MPa,σ0.2达185MPa.     

V-5Cr-5Ti合金的拉伸性能及其强化机理

对真空熔炼V-5Cr-5Ti合金开展了均匀化退火、热锻开坯、冷轧变形和热处理实验,利用万能试验机、扫描电镜（SEM）和透射电镜（TEM）研究了V-5Cr-5Ti合金中析出相对力学性能影响,估算了V-5Cr-5Ti合金中析出相强化的效果。结果表明：铸态V-5Cr-5Ti合金存在以片层状析出相为特征的树枝状析出相,合金均匀化退火后析出相由片层状转化为针状,由树枝状转化成团聚状。析出相在变形过程中破碎成短条状或球状颗粒。铸态合金的抗拉强度、屈服强度和延伸率的平均值分别为505.0 MPa、415.0 MPa和8.2%,断裂机制为脆性的解理断裂。均匀化热处理后断裂机制转变为沿晶断裂和准解离断裂共存的混合型断裂。80%冷变形＋热处理后合金的抗拉强度、屈服强度和延伸率的平均值分别为487.3 MPa、382.7 MPa和26.2%,由于晶粒及析出相形态的变化,合金塑性得到大幅改善。锻造和冷轧后合金断裂机制为韧性的微孔型断裂。析出相以Orowan强化机制增强V-5Cr-5Ti合金,以80%冷轧1000 ℃/1 h退火状态合金为例,由析出相强化获得的屈服强度增量约为50.1 MPa。     

Si对热挤压Cu-15Ni-8Sn合金组织和力学性能的影响

采用光学显微镜、扫描电镜和力学性能测试等方法研究了Si含量对热挤压态Cu-15Ni-8Sn合金微观组织和力学性能的影响。结果表明:Si可细化铸态合金的枝晶间距,含Si相经过长时间的均匀化退火后仍能稳定存在于合金内;Si元素能明显抑制热挤压态合金再结晶晶粒的长大和二次再结晶过程。Si含量为0.3%时,可得到分布均匀、晶粒细小的再结晶组织,晶粒尺寸5~8μm,合金抗拉强度795 MPa,屈服强度589 MPa,伸长率31.2%,分别比不含Si的合金提高9.3%、13.1%和20.3%。     

循环扩-挤变形AZ80镁合金组织与性能

通过循环扩挤(CEEOP)变形方法对100 mm×50 mm×170 mm的AZ80镁合金块状材料进行挤压加工,借助计算机模拟仿真、组织观察、拉伸试验、硬度测试等手段研究了1~4道次CEEOP变形对AZ80镁合金等效应变、显微组织和力学性能的影响。结果表明:随着CEEOP挤压道次的增加,晶粒的尺寸越来越小且分布均匀,1道次后晶粒尺寸可以从200μm左右细化到6μm,4道次后晶粒尺寸细化到1.5μm左右,整体分布均匀呈等轴晶晶粒,晶粒细化的机制是晶粒的机械破碎和动态再结晶,2道次以后晶粒细化效果不太明显。力学性能较均匀化退火态有了大幅度的提升,1道次硬度HB从均匀化退火态的615 MPa提升到了830.7 MPa,4道次达到862.7 MPa,抗拉强度与屈服强度分别从均匀化退火态的230.9和115 MPa提升到了262.7和155 MPa,4道次可以达到294和170 MPa,通过对比ECAP变形试样的组织与力学性能数据,在相同的变形温度与累积应变下,CEEOP变形方法比ECAP变形能够更好地细化晶粒和提高材料的抗拉强度和屈服强度。     

Al-Cu-Mg合金在快速冷冲及再结晶退火过程中的显微组织演变（英文）

采用透射电镜技术(TEM)系统研究喷射成形快速凝固细晶Al-Cu-Mg合金在快速冷冲及再结晶退火工艺过程中的显微组织演变。结果表明:细晶Al-Cu-Mg合金在快速冷冲及再结晶退火过程中的析出相主要为S相,还有少量较粗的Al_6Mn相;随着变形道次的增加,析出相的密度不断增大、尺寸显著减小,形变带和过渡带逐渐消失,晶粒组织不断细化并趋于均匀。快速冷冲引入的缺陷有助于Al-Cu-Mg合金脱溶和再结晶形核,促进S相和再结晶的形核与长大。较粗晶粒中的形变带及过渡带在形变和再结晶过程中转变为形变诱生晶界,从而细化晶粒、获得均匀纳米晶组织和促进S相弥散分布。     

循环扩-挤变形AZ80镁合金组织与性能研究

通过循环扩挤(CEEOP)变形方法对100mm×50mm×170mm的 AZ80镁合金块状材料进行挤压加工,借助计算机模拟仿真、组织观察、拉伸试验、硬度测试等手段研究了1～4道次CEEOP变形对AZ80镁合金等效应变、显微组织和力学性能的影响。结果表明：随着CEEOP挤压道次的增加,晶粒的尺寸越来越小且分布均匀,1道次后晶粒尺寸可以从200μm左右细化到6μm,4道次后晶粒尺寸细化到1.5μm左右,整体分布均匀呈等轴晶晶粒,晶粒细化的机制是晶粒的机械破碎和动态再结晶,2道次以后晶粒细化效果不太明显。力学性能较均匀化退火态有了大幅度的提升,1道次硬度从均匀化退火态的61.5HB提升到了83.07HB,4道次达到86.27HB,抗拉强度与屈服强度分别从均匀化退火态的230.9MPa和115MPa提升到了262.7MPa和155MPa,四道次可以达到294MPa和170MPa,通过对比ECAP变形试样的组织与力学性能数据,在相同的变形温度与累积应变下,CEEOP变形方法比ECAP变形能够更好地细化晶粒和提高材料的抗拉强度和屈服强度。     

LPSO相对多向锻造过程中Mg_(96)Zn_1Gd_3镁合金再结晶行为的影响

采用均匀化炉冷与均匀化水冷两种热处理工艺,获取了含与不含长周期堆垛结构(LPSO)相的两种初始态Mg_(96)Zn_1Gd_3合金,探究了LPSO相对合金多向锻造变形过程中动态再结晶行为的影响。结果表明,随着变形道次的增加,两种合金中的再结晶体积分数逐渐增大、晶粒尺寸显著细化。在相同道次变形条件下,相比于不含LPSO相的合金变形组织,含LPSO相的合金变形后组织再结晶体积分数更高,LPSO相的存在促进了合金的动态再结晶。     

电脉冲连续退火对AZ91镁合金带材组织和性能的影响

研究了电脉冲连续退火对冷轧时效态AZ91镁合金带材显微组织和力学性能的影响。结果表明:电脉冲退火在较低的温度下快速完成了α-Mg基体的再结晶,可显著细化晶粒。当退火温度为210℃时,α-Mg基体发生完全再结晶,其平均晶粒尺寸由冷轧态的约30μm减小为约7μm,带材的抗拉强度由冷轧态的410 MPa减小至334 MPa,断后伸长率由冷轧态的3.7%增大至23%。电脉冲退火后带材的拉伸断裂方式由冷轧态的脆性沿晶断裂转变为韧性穿晶断裂。电脉冲在其热效应和非热效应的共同作用下快速完成再结晶过程以及β-Mg17Al12相阻碍α-Mg基体晶粒长大,是电脉冲退火细化晶粒的主要原因。     

挤压ZAT522镁合金的组织与力学性能研究

研究了均匀化态与挤压态Mg-5Zn-2Al-2Sn(ZAT522)合金的微观结构、织构和力学性能。结果表明:挤压合金为完全动态再结晶结构,具有双峰晶粒尺寸。挤压合金的平均晶粒尺寸为11.2μm,在晶界与晶粒内部析出了大量细小Mg2Sn相,析出相的不均匀分布是导致双峰晶粒结构的主要原因;挤压合金中形成强的基面织构。此外,与均匀化合金相比,挤压的ZAT522合金具有优异的力学性能,其抗拉强度255 MPa、屈服强度114 MPa、伸长率32%。挤压合金强度显著增加主要归因于晶粒细化、沉淀强化和织构强化。     

中间退火工艺对6016铝合金组织与性能的影响

通过扫描电镜、透射电镜等手段研究了汽车外板用6016铝合金生产过程中微观结构的演变规律和中间退火工艺对综合性能的影响。结果表明,连续退火比箱式退火具备更强的晶粒细化作用;中间退火前冷轧压下量对结晶相破碎效果显著,结晶相尺寸从4.38 μm降至3.20 μm左右,降低了约27%;中间退火处理弱化了T4P态板材中的不均匀屈服延伸。箱式退火的慢升温速率和长时间中温保温导致Mg₂Si相沿晶析出并粗化。     

等温多向锻造AZ61镁合金的组织演化与力学性能

研究AZ61镁合金在等温锻造过程中的显微组织及力学性能变化,讨论晶粒细化机理及显微组织与力学性能的关系。结果表明：合金的平均晶粒尺寸随着多向锻造道次的增加而减小,在初始的1、2道次变形过程中,晶粒急剧细化,随着变形道次的增加,晶粒细化能力减弱,经过6道次变形后,晶粒尺寸由初始的148gm细化到14μm。晶粒细化主要是由于合金在锻造过程中发生了连续动态再结晶。随着变形道次的增加,合金的抗拉强度、屈服强度和伸长率逐渐增加。     

Effects of Passes on Microstructure Evolution and Mechanical Properties of Mg–Gd–Y–Zn–Zr Alloy During Multidirectional Forging

The multidirectional forging(MDF) process was conducted at temperature of 753 K to optimize the mechanical properties of as-homogenized Mg–13 Gd–4 Y–2 Zn–0.6 Zr alloy containing long-period stacking ordered phase. The effects of MDF passes on microstructure evolution and mechanical properties were also investigated. The results show that both the volume fraction of dynamic recrystallization(DRX) grains and mechanical properties of the deformed alloy enhanced with MDF passes increasing till seven passes. The average grain size decreased from 76 to 2.24 lm after seven passes, while the average grain size increased to 7.12 lm after nine passes. The microstructure after seven passes demonstrated randomly oriented fine DRX grains and larger basal(0001)\11"20[ Schmid factor of 0.31. The superior mechanical properties at room temperature(RT) with ultimate tensile strength(UTS) of 416 MPa and fracture elongation of 4.12% can be obtained after seven passes. The mechanical properties at RT after nine passes are inferior to those after seven passes due to the coarsening of DRX grains, which can be ascribed to the static recovery resulting from the repeated heating at the interval of MDF passes. The elevated temperature mechanical properties of the deformed alloy after seven passes and nine passes were investigated. When test temperature was below 523 K, the elevated temperature tensile yield strength and UTS after seven passes are superior to those after nine passes, while they are inferior to that after nine passes as temperature exceeds523 K.     

固溶处理对TC11钛合金组织与性能的影响

通过光学显微镜、扫描电镜、X射线衍射仪以及室温拉伸性能测试,研究TC11钛合金分别在955、975、995和1015℃固溶处理后的微观组织与力学性能的对应关系。结果表明,合金原始锻态显微组织为α+β两相区锻造形成的双态组织,以α_p相和β转变组织为主。经固溶处理后,原始锻态组织中被扭转和拉长的α_p相随着固溶温度升高逐渐变小、变圆,同时体积较小的α_p相逐渐消失。固溶温度为995℃时,合金强度达到最大值,抗拉强度(R_m)为1403 MPa,屈服强度(R_p0.2)为1158 MPa;固溶温度为955℃时,合金塑性最佳,断后伸长率(A)为9.5%,断面收缩率(Z)为32%。当固溶温度位于两相区时,其拉伸断口微观形貌相似,均以韧窝为主;当固溶温度位于单相区时,断口形貌结晶状明显,且有较大的撕裂棱,在岩石状表面有大量撕裂状小韧窝。     

非对称挤压腔循环膨胀挤出法制备AZ31合金的显微组织和力学性能

研究AZ31合金在非对称挤压腔循环膨胀挤出(CEE-AEC)过程中的显微组织、织构演化和力学性能.结果表明,在CEE-AEC过程中发生连续动态再结晶(CDRX)和不连续动态再结晶(DDRX).经过3道次变形后,变形试样的显微组织得到细化,非对称型腔区域合金的平均晶粒尺寸为6.9μm.随着道次的增加,基体织构的最大强度增...     

Microstructures and mechanical properties of double hot-extruded AZ80＋xSr wrought alloys

The effects of Sr addition on microstructures and tensile properties of the as-cast and hot-extruded AZ80 alloys were studied by OM, SEM, EDS, XRD, DSC and Instron tester. The results show that the microstructures of as-cast alloys consist of a-Mg and β-Mg17Al12 phase. Sr gathers on the boundaries, and dissolves into β-Mg17Al12 phase or forms Mg17Sr2 phase. The grains of ascast alloys are refined and discontinuous net-shaped structure is formed. The compound phases on the boundaries become thicker with increasing Sr content. The ultimate tensile stress（UTS） and elongation are improved compared with the corresponding Sr-free alloy. After preliminary hot-extruding, the UTS is up to 308-320 MPa and elongation reaches 8.0%-13.5%. After double hot-extrusion, the dynamic recrystallization completes totally, and the UTS is up to 310-355 MPa, but the elongation does not change apparently. The alloy with 0.02%Sr （mass fraction） obtains the best comprehensive performance with the UTS of 355 MPa and elongation of 13.2%. The SEM morphology of fracture surface shows that the alloys with Sr present good ductility after double hot-extrusion.     

Simultaneous improvement in strength and ductility of extruded Mg alloy via novel closed forging extrusion

A novel continuous plastic process employed on AZ31 Mg alloy called closed forging extrusion (CFE) was presented. The optical microscopy, scanning electron microscopy, electron back-scatter diffraction and tensile and compressive tests were employed to investigate the microstructure evolution and strengthening mechanism. The results indicated that the CFE-process can promote dynamic recrystallization (DRX), eliminate the coarsen unDRXed grain regions, refine the grains effectively, and improve the strength, plasticity and anisotropy of the alloy. The grain refinement was mainly attributed to the stress, which facilitated the nucleation of recrystallization and refined the microstructure via the CFE. The fully DRXed ultrafine grained structure improved the strength and plasticity simultaneously. After 60 s closed forging and continuous extrusion, the alloy exhibits relatively high TYS, UTS, CYS, elongation and yield asymmetry of 305 MPa, 337 MPa, 295 MPa, 27% and 0.97, respectively.     

锻压态AZ61镁合金的变形行为

对模压态AZ61镁合金在室温～150℃条件下的的力学性能及变形机制进行研究.结果表明:在拉伸速度1 mm/min,随着拉伸温度的升高,拉伸后的显微组织中晶界逐渐软化,动态再结晶有减少趋势,并伴随有孪晶出现,抗拉强度及屈服强度显著下降,而其伸长率在低温拉伸中的变化幅度有限;同时在90 ～ 130℃发生了动态应变时效;对拉伸断口的观察分析表明,随着温度的逐渐升高(≤150℃),其断裂机制由韧脆混合断裂逐渐变为韧性断裂.     

Microstructures and Mechanical Properties of Mg–xAl–1Sn–0.3Mn( x = 1, 3, 5) Alloy Sheets

The influence of Al alloying on the microstructures and the mechanical properties of Mg–x Al–1 Sn–0.3 Mn alloy sheets was investigated. The microstructure of Mg– x Al–1 Sn–0.3 Mn consisted of α-Mg and Mg 17 Al 12 precipitates. Alloying with Al increased the amount of Mg_(17)Al_(12) and the average grain size. Uniaxial tensile tests were carried out along the extrusion direction(ED), the transverse direction(TD) and 45° toward the ED. Mg–5 Al–1 Sn–0.3 Mn alloy sheet exhibited the best combination of mechanical properties along the ED: a yield strength of 142 MPa, an ultimate tensile strength of 282 MPa and an elongation of 23%. The good performance of Mg–5 Al–1 Sn–0.3 Mn sheet was mainly attributed to the large quantity of Mg_(17)Al_(12) precipitates and a weak basal texture. Annealing caused static dynamic recrystallization, refined the grain size and enhanced the mechanical properties: yield strength of 186 MPa, ultimate tensile strength of 304 MPa, elongation of 21% along ED. Both strength and ductility were enhanced by Al alloying.     

双级时效热处理ZM5合金的显微组织和力学性能

以ZM5合金为研究对象,通过显微组织分析和力学性能测试等手段,研究了其不同状态的显微组织和力学性能。结果表明,铸态ZM5合金中存在呈网状分布的粗大不规则块状β-Mg₁₇Al₁₂相;固溶处理后,β-Mg₁₇Al₁₂相溶入α-Mg基体中,仅有少量残余的AlMn相;经T6处理后,沿晶界析出片层状β-Mg₁₇Al₁₂相;经双级时效处理后,沿晶界析出片层状β-Mg₁₇Al₁₂相及在晶内析出细小的针片状β-Mg₁₇Al₁₂相。与铸态相比,热处理后ZM5合金的抗拉强度大幅提升;经双级时效处理后,其抗拉强度可达285MPa,比T6处理后的抗拉强度高20MPa。     

Al-Cu-Li合金搅拌摩擦焊接头的微观组织和力学性能

采用搅拌摩擦焊方法对2mm厚的Al-Cu-Li合金轧制板进行了焊接.接头内形成了焊核区、热机影响区和热影响区.焊核区由细等轴再结晶组织构成;热机影响区内的组织发生较大的弯曲变形,并在热循环的作用下发生了回复反应;热影响区形成了粗大的板条状组织.实验结果表明:在200mm/min的焊接速度下,接头的拉伸强度最高,达到393MPa,断裂形式为韧性和脆性的混合型断裂;在500mm/min的焊接速度下,接头强度为267.7MPa,断裂形式为脆性断裂.