Nd对挤压铸造镁合金组织和力学性能的影响

镁合金经Ca合金化处理和稀土Nd变质处理后,在100MPa压力下挤压铸造成形,研究了Nd对Mg-8Al-1.0Ca合金组织和性能的影响。经XRD扫描及EDS能谱分析发现,通过挤压铸造,使得镁合金晶粒细化,有利于位错形成,析出相变得均匀细小,力学性能明显改善;当Nd添加量为0.4%时,镁抗拉强度达到230MPa,屈服强度为121MPa,伸长率为4.8%,合金性能达到最佳,较未变质时分别提高了28%、61%和78%。     

热处理对消失模铸造镁合金组织及力学性能的影响

对不同热处理工艺条件下消失模铸态镁合金的组织、力学性能进行了系统的研究,结果表明,高温时效沉淀在晶内及晶界处以连续形式析出,而在低温时效时沉淀以不连续形式在晶界形成,并具有糖浆状.经过热处理后合金的综合力学性能有较大幅度的提高,其中高温时效对提高强度及加工硬化率尤为有利.还通过硬度、电阻率测量分别研究了固溶、时效过程动力学.由于原子扩散速度随温度的升高而增大,高温时效(380℃)的硬度峰仅过10 h即出现,而在低温时效(150℃)时经过24 h仍未达到硬度峰.     

Bi对铸造镁合金组织和力学性能的影响

研究了Ｂｉ对铸造镁合金显微组织和力学性能的影响。结果表明,添加适量Ｂｉ可以改善镁合金显微组织,从而使合金的室温和高温力学性能明显提高,但塑性有所降低。     

ZA53镁合金的砂型铸造组织和力学性能研究

研究发现砂型铸造镁合金ZA53的主要相组成为δ-Mg基体相和τ[Mg32（Al，Zn）49]化合物相，τ相以半连续网状沿δ相晶界分布。对ZA53合金进行的固溶处理试验发现，在335℃固溶17h淬火后，合金室温抗拉强度和塑性得到大幅提高。在343℃固溶17h淬火后，合金组织完全转变为单相固溶体，合金的室温力学性能较好，σb=245MPa，伸长率为12％，合金的拉伸断口形貌由混合型断口转变为韧性断口。     

铸造工艺对WE54镁合金显微组织和力学性能的影响

对比研究了金属型铸造和树脂砂铸造WE54合金的显微组织和力学性能。结果表明,金属型铸造和树脂砂铸造WE54合金具有相似的铸态组织,但是由于冷却速度较慢,树脂砂铸造WE54合金的显微组织更加粗大,铸态组织中第二相的含量较少。金属型铸造的力学性能优于树脂砂铸造WE54合金,两者在峰值时效(T6)状态下的抗拉强度分别为327 MPa和261 MPa,屈服强度分别为234 MPa和209 MPa。造成树脂砂铸造WE54合金强度较低的主要原因是晶粒尺寸更为粗大。此外,树脂砂铸造合金中存在的缩松缺陷也使得合金的抗拉强度降低。     

消失模重力铸造镁合金组织及性能研究

对消失模重力铸造及随后热处理条件下AZ91合金组织、力学性能进行了系统的研究。结果表明：消失模铸态下的合金除主要由初生α-Mg枝晶及离异共晶沉淀相β—Mg17Al12组成外，还存在其他工艺条件下未曾发现的新相Al32Mn25(线尺寸为5～50μm)；消失模铸态下的AZ91合金各项力学性能指标均高于树脂砂型铸态的各对应值，这可以归因于消失模铸造充型过程中存在的泡沫模冷却作用及缓冲作用；经过热处理后合金的综合力学性能有较大幅度的提高，均匀化过程中各元素扩散速度较慢。     

Be对铸造Mg合金组织和力学性能的影响

研究了在Ｍｇ－９Ａｌ－０．５Ｚｎ－１ＲＥ合金中添加Ｂｅ后合金组织和力学性能的变化规律。Ｂｅ的加入对γ相有一一的变质作用，相的形状和分布随Ｂｅ含量的变化而变化。Ｂｅ的加入量少时，合金铁常温抗拉强度σｂ，σ０．２与伸长率δ都有所下降；当Ｂｅ的加入量增加到一定程度时，这些性能指标反而升高。继续加入是地，性能又会下降。高温拉伸性能的变化趋势与常温时相同，Ｂｅ的另入时对α－Ｍｇ基体的显微硬度影响不大。     

离心铸造AZ61A镁合金管的显微组织和力学性能

利用离心铸造工艺制备大口径AZ61A镁合金薄壁管,研究了其显微组织及力学性能,与传统砂型凝固铸件进行了比较分析。结果表明,离心铸造镁合金管晶粒得到了显著的细化;平衡凝固条件下的L→α-Mg＋β-Mg17Al12共晶转变在很大程度上被抑制,形成以过饱和初生相α-Mg为主相的凝固组织;合金元素的整体分布均衡;力学性能得到提高,断口上存在大量韧窝,具有准解理断裂特性,显示塑性得到了明显改善     

Mg-Al-Zn-Mn系铸造镁合金力学性能研究

开发了一种适合重力铸造的Mg-Al-Zn-Mn系镁合金,并研究了其力学性能与成分之间的关系,找出最优化的合金成分Mg-9Al-0.8Zn-0.3Mn,经T6工艺热处理后,室温下抗拉强度为270MPa,屈服强度为162MPa、伸长率为3.88%.同时分析了T6热处理前后合金力学性能变化的原因以及显微组织特征.     

Mg-Nd-Gd-Zn-Zr镁合金铸造组织与力学性能

采用正交试验方法,通过砂型铸造制备9种不同成分的Mg-Nd-Gd-Zn-Zr系镁合金。研究该系列镁合金的铸造组织和室温力学性能,并通过对力学性能试验数据的分析,研究主要合金化稀土元素Gd和Nd的作用。研究发现:该系列镁合金铸态组织为α-Mg基体和Mg12Nd化合物。经过固溶处理后,铸态组织中晶界上的化合物大部分溶入基体,但在晶界上还有一些颗粒状的化合物。Gd含量越高,合金的室温抗拉强度、屈服强度和延伸率就越高。Nd含量越高,抗拉强度和屈服强度也越好,但延伸率在Nd含量超过2水平(2.85%)后会降低。抗拉强度和屈服强度受Nd含量的影响最大,Gd含量的影响次之。Zn含量越高屈服强度越高,但抗拉强度和延伸率降低,其中延伸率受Zn含量的影响最大。     

机械振动对铸造铝合金组织和性能的影响

分析振动方式对ZL101铝合金消失模铸件组织和力学性能的影响。结果表明,机械振动后合金组织明显细化;垂直振动时,合金晶粒尺寸最小,孔隙率最低,抗拉强度最大;ZL101合金垂直振动后,不同厚度处的组织存在较大差别,厚度越大,振动细化效果越显著。     

Microstructure and mechanical properties of die-cast AZ91D magnesium alloy by Pr additions

Mg-9Al-xPr (x=0.4, 0.8 and 1.2, mass fraction, %) magnesium alloys were prepared by high-pressure die-casting technique. The effects of Pr on the microstructures of die-cast Mg-9Al based alloy were investigated by XRD and SEM. Needle-like Al11Pr3 phase and polygon Al6Mn6Pr phase are found in the microstructure. With 0.4% Pr addition, fine needle-like Al11Pr3 phase and a small amount of polygon Al6Mn6Pr phase near the grain boundary are found in the microstructure. Increasing Pr addition to 0.8%, lots of coarse needle-like Al11Pr3 phase within grain and polygon Al6Mn6Pr phase on grain boundary are observed. Further increasing Pr addition, the size of needle-like Al11Pr3 phase decreases, while the size of polygon Al6Mn6Pr relatively increases. The mass fraction of Pr at around 0.8% is considered to be suitable to obtain the optimal mechanical properties. The optimal mechanical properties are mainly resulted from grain boundary strengthening obtained by precipitates and solid solution.     

热挤压AZ80镁合金管材的组织与力学性能

对AZ80镁合金管材的挤压工艺进行研究,对挤压前后材料的组织与力学性能进行分析。结果表明,经过热挤压后,镁合金的晶粒细化,力学性能有较大提高。晶粒尺寸由挤压前铸态的28μm细化到挤压后的4μm,抗拉强度由162 MPa提高到265 MPa,屈服强度由74 MPa提高到180 MPa,伸长率由4%提高到14%。随着挤压比的增加,晶粒细化明显,伸长率和屈服强度增加。对于挤压AZ80镁合金管材,合理的挤压工艺参数：挤压比为18.2,坯料温度为390℃,模具预热温度为360℃,挤压速度为1 mm/s,凹模锥半角为60°-70°。     

往复挤压AM60B镁合金的组织与力学性能

通过往复挤压（CEC）变形来细化AM60B镁合金的组织。结构表明：随着CEC道次的增加,组织得到明显细化。当材料达到临界最小晶粒尺寸时,进一步挤压变形也很难使组织得到明显的细化。细小的组织具有优异的力学性能,合金的硬度、屈服强度、抗拉强度和断后伸长率分别由铸态的62．3、64MPa、201MPa和11％上升N-道次变形后的72．2、183．7MPa、286．3MPa和14．0％。但是再进一步挤压变形材料的力学性能增加幅度不明显,经四道次挤压变形后其硬度、屈服强度、抗拉强度和断后伸长率分别为73．5、196MPa、297MPa和16％     

汽车用AZ31镁合金激光熔覆Al-Si涂层的组织与性能

通过激光熔覆Al-Si涂层的方法对AZ31镁合金表面进行了改性,研究了熔覆层的物相组成、显微组织、显微硬度、耐磨性和耐腐蚀性能。结果表明,熔覆层主要由Mg₂Si、Mg₁₇Al₁₂、Al₃Mg₂、Al₂Mg相组成,与基体呈冶金结合,硬度最高达到152 HV;耐磨性和耐腐蚀性较好,磨损失重及腐蚀速率分别为基体的1.75倍和1.88倍。     

Microstructure and mechanical properties of magnesium alloy prepared by lost foam casting

The microstructure and mechanical properties of AZ91 alloy prepared by lost foam casting(LFC) and various heat treatments have been investigated. The microstructure of the AZ91 alloy via LFC consists of dominant α-Mg and β-Mg17Al12 as well as a new phase Al32 Mn25 with size of about 5-50μm, which has not been detected in AZ91 alloy prepared by other casting processes. The tests demonstrate that the as-cast mechanical properties are higher than those of sand gravity casting because of chilling and cushioning effect of foam pattern during the mould filling. The solution kinetics and the aging processes at different temperatures were also investigated by hardness and electrical resistivity measurements. The kinetics of aging are faster at the high temperature due to enhanced diffusion of atoms in the matrix, so the hardness peak at 380℃ occurs after 10 h; while at the lower aging temperature(150℃), the peak is not reached in the time(24 h) considered.     

Microstructure and mechanical properties of Mg-6Al magnesium alloy with yttrium and neodymium

The effects of rare earth (RE) elements Y and Nd on the microstructure and mechanical properties of Mg-6Al magnesium alloy were investigated. The results show that a proper level of RE elements can obviously refine the microstructure of Mg-6Al magnesium alloys, reduce the quantity of/β-Mg17Al12 phase and form Al2Y and AI2Nd phases. The combined addition of Y and Nd dramatically enhances the tensile strength of the alloys in the temperature range of 20-175℃. When the content of RE elements is up to 1.8%, the values of tensile strength at room temperature and at 150℃ simultaneously reach their maximum of 253 MPa and 196 MPa, respectively.The main mechanisms of enhancement in the mechanical properties of Mg-6Al alloy with Y and Nd are the grain refining strengthening and the dispersion strengthening.     

AZ31B镁合金冷轧及退火后的组织与性能

研究了AZ31B镁合金的冷轧工艺与冷轧后的组织变化,以及退火过程中退火温度、保温时间以及冷轧变形量对再结晶组织的影响,获得了静态再结晶图.当冷轧变形量大于15%,退火温度不超过400 ℃,可以获得细小的再结晶晶粒.最佳的冷轧及退火工艺为:冷轧变形量15%～25%,退火温度200～350 ℃,时间为30～60 min.冷轧退火AZ31B镁合金板材具有较好的力学性能,应变速率对镁合金冷轧退火板材的伸长率影响较大,而应变速率对强度基本上没有影响.     

半固态挤压铸造铜合金组织和力学性能研究

以半固态ZCuSn10P1铜合金为研究对象,自主设计了1套1模4件挤压模具并进行了半固态挤压铸造成形实验,研究了成形比压和挤压速率对半固态ZCuSn10P1铜合金挤压铸造组织和性能的影响规律。结果表明:当成形比压由180 MPa增加到250 MPa时,半固态铜合金平均晶粒直径逐渐减小,由89.25μm减小至77.96μm,液相率由36.7%减少至22.3%,抗拉强度由318 MPa增加至387 MPa,提高了21.70%,延伸率由4.2%降至2.8%;当挤压速率由11 mm/s增加至15 mm/s时,固相晶粒圆整度由1.54减小至1.32,此时抗拉强度由368 MPa增加至387 MPa,提高了5.16%,延伸率由3.3%降低至2.8%。     

Microstructure and mechanical properties of AZ91D magnesium alloy by expendable pattern shell casting with different mechanical vibration amplitudes and pouring temperatures

To refine the microstructure and improve the mechanical properties of AZ91 D alloy by expendable pattern shell casting(EPSC),the mechanical vibration method was applied in the solidification process of the alloy.The effects of amplitude and pouring temperature on microstructure and mechanical properties of AZ91 D magnesium alloy were studied.The results indicated that the mechanical vibration remarkably improved the sizes,morphologies and distributions of the primaryα-Mg phase andβ-Mg17 Al12 phase,and the densification and tensile properties of the AZ91 D alloy.With an increase in amplitude,the microstructures were gradually refined,resulting in a continuous increase in mechanical properties of the AZ91 D alloy.While,with the increase of pouring temperature,the microstructures were continuously coarsened,leading to an obvious decrease of the mechanical properties.The tensile strength and yield strength of the AZ91 D alloy with a vibration amplitude of 1.0 mm and a pouring temperature of 730℃were 60%and 38%higher than those of the alloy without vibration,respectively.