铈对铸造镁合金AZ91D显微组织与力学性能的影响

利用光学金相显微镜OM和XRD分析了分别加入0．1％，0．3％，0．5％，0．7％和1．0％Ce的AZ91D合金显微组织和相组成，测试了室温力学性能和硬度。结果表明，加入一定量Ce后的AZ91D合金形成杆状化合物Al4Ce，被推移到生长界面，阻碍枝晶的自由生长，从而细化合金显微组织；Ce能提高AZ91D合金室温抗拉强度和硬度，而对其屈服强度和延伸率影响不大；加入0．7％Ce的AZ91D合金晶粒细化效果好，其综合力学性能比较理想。     

Mg-30Sr对AZ91D镁合金显微组织和力学性能的影响

为了开发低成本、高强度的新型镁合金．研究了微量Sr对AZ91D镁合金显微组织和力学性能的影响。研究结果表明：Sr加入AZ91D镁合金,能明显细化组织晶粒。从而改善合金的室温力学性能。当加入1％Sr（质量分数）时,合金晶粒细化效果较好。其室温力学性能和硬度比原来都有较大的提高。     

Al-Ti-B对AZ91D镁合金显微组织和力学性能的影响

研究了Al-Ti-B对AZ91D镁合金铸态显微组织和力学性能的影响，并探讨其化学成分与组织结构和力学性能之间的变化。研究结果表明：Al-Ti-B加入AZ91D镁合金，能明显细化组织晶粒，从而改善合金的室温力学性能。当加入Al-Ti-B时，合金晶粒细化效果较好，其室温力学性能和硬度比原来都有较大的提高。     

熔剂FHRJ对含铈AZ91D镁合金组织和性能的影响

通过对传统熔剂RJ-2和自制熔剂FHRJ对含铈AZ91D镁合金的显微组织和力学性能的研究对比,表明:含铈AZ91D镁合金采用自制熔剂FHRJ熔炼后,Mg17Al12相得到改善,晶内出现Al4C3形核质点,晶粒更细小,合金的抗拉强度、屈服强度及延伸率等力学性能也比传统覆盖熔剂RJ-2更好。     

铈镧混合稀土对AZ91D压铸镁合金显微组织和蠕变性能的影响

研究了不同含量Ce/La(x=0,0.1,0.5,1.0)对AZ91D镁合金显微组织及蠕变性能的影响。通过X射线衍射(XRD)、金相显微镜(OM)、扫描电镜(SEM)及能谱分析(EDX)观察与分析表明,压铸AZ91D镁合金中添加Ce/La后,除了α-Mg,β-Mg17Al12相之外,还生成了新的稀土化合物Al11RE3(RE=Ce/La)化合物,并且细化了合金显微组织、提高了合金室温和高温力学性能。生成的Al11RE3(RE=Ce/La)高温热稳定相使AZ91D+xCe/La(x=0,0.1,0.5,1.0)合金在150℃,50MPa下的蠕变抗力优于AZ91D镁合金,1%Ce/La的合金与AZ91D相比,蠕变延伸率低了0.2%,最小蠕变速率从2.30×10-8s-1降低到2.02×10-8s-1。蠕变试样的微观组织结构分析表明:AZ91D合金的蠕变机制主要以晶界滑移方式为主,Al11RE3(RE=Ce/La)热稳定相在晶界处延缓和阻碍了晶界断裂的过程。     

稀土元素Gd、Ce对AZ31镁合金的硬化行为

将变形AZ31镁合金作为研究对象,研究了将不同含量的元素Gd和Ce加入该合金模型之后形成的AZ31-8Re镁合金的力学性能和铸态组织等特性以及镁合金的金相微观组织和力学性能,系统地比较了不同含量的稀土元素对镁合金力学性能的影响,探讨了稀土元素Gd和Ce对AZ31变形镁合金的金相组织的影响以及对其的时效硬化行为。     

稀土元素Gd、Ce对AZ31镁合金硬度的影响

本文以AZ31变形镁合金为研究对象,在其基础上添加了不同含量的稀土元素Gd和Ce,研究AZ31-8Re镁合金的铸态组织和性能.利用光学金相显微镜、维氏硬度测试仪等实验设备研究镁合金的相的微观组织和力学性能,系统地比较了不同含量的稀土元素Gd和Ce的镁合金的性能,分析了不同含量的稀土元素Gd和Ce对镁合金力学性能的研究了稀土元素Gd和Ce对AZ31变形镁合金的组织和力学性能的影响.     

AZ91D镁合金半固态浆料制备过程中的组织演变

对AZ91D镁合金进行了半固态等温热处理,通过光学显微镜、扫描电镜对其组织进行了研究。结果表明,AZ91D镁合金铸件经过580℃×30min半固态等温热处理后,合金显微组织中β-Mg17Al12相基本熔入基体,枝晶状的铸态组织在等温处理过程中变得细小圆整。     

Ce元素对AZ80镁合金显微组织及铸造成形性的影响

通过OM、SEM等研究了Ce元素对AZ80镁合金显微组织及铸造成形性能影响。研究结果表明,AZ80+Ce合金中除Mg17Al12相外,在基体内部分布细小颗粒状Mg-Ce稀土相,细化了AZ80镁合金铸棒中粗大的第二相,提高了AZ80镁合金的组织均匀性,从而增强了AZ80合金的铸造成形性。     

稀土对AZ91镁合金组织和性能影响的研究进展

AZ91合金是实际使用最为普遍的一类镁合金,在现有压铸镁合金中AZ91约占90%。稀土元素的独特性质能够影响合金性能,因此在AZ91合金中添加稀土元素,以期改善其性能是目前研究的一个热点。综述了稀土元素对AZ91合金铸造过程中的净化作用,以及对AZ91合金组织的细化作用;论述了稀土元素对AZ91合金力学性能,摩擦磨损性能,耐腐蚀性能的影响。     

Pb对AZ91镁合金铸态显微组织及力学性能的影响

采用扫描电镜观察、电子探针分析及拉伸性能测试等方法研究了Pb的添加对AZ91合金显微组织和力学性能的影响。结果表明,Pb能够细化AZ91镁合金中的d—Mg和β-Mgl7Al12的晶粒,抑制二次B的析出,且Pb可改善β-Mgl7Al12相形态和分布。Pb通过细晶强化增加了合金强度和硬度,使合金的断裂机制从脆性解理断裂转变为准解理断裂。     

Study on Ignition Proof AZ91D Magnesium Alloy Chips with Cerium Addition

The effect of Ce on ignition point of AZ91D magnesium alloy chips was studied. For the AZ91D and the AZ91D-xCe magnesium alloys, changing the sizes of the chips in the range of 58 - 270 μm has a limited influence on ignition point, however, the shift of the content of Ce has much effect on ignition point. Increasing the Ce content, x from 0.15 to 0.25, the ignition point increases with increasing of Ce; however, x from 0.25 to 0.45, the ignition point decreases with increasing of Ce. By the addition of Ce of 0.25 %. the ignition point is raised by 43℃.     

High Cycle Fatigue Properties of Die-Cast Magnesium Alloy AZ91D with Addition of Different Concentrations of Cerium

Recently , magnesiumalloy has become a very at-tractive material because of its lowdensity ,high spe-cific strength, and easy recyclability compared withother metals[1].As alight structural material ,recentlythere has been a significantincreaseinthe use of mag-nesiumalloy for automobiles ,aerospace components ,computers , mobile phones , and household equip-ments[2 ,3]. Mg-Al-Zn (AZ91D) alloyis the most wide-ly used die-cast magnesiumalloyin automotive applica-tions due toits excellent casta…     

Effect of mischmetal on mechanical properties and microstructure of die-cast magnesium alloy AZ91D

Effects of the mischmetal addition in range of 0.4 wt.% to 1.7 wt.% on the microstructure and mechanical properties of die-cast magnesium AZ91D were investigated to improve the elevated temperature mechanical properties of the alloy by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and tensile tests. The results revealed that mechanical properties of die-cast magnesium alloy AZ91D-0.4%MM at 100 oC were near to those of die-cast magnesium alloy AZ91D. The ultimate tensile strength, 0.2% proof yield strength and elongation to failure of die-cast magnesium alloy AZ91D at 170 oC were 178, 129 MPa and 20%, respectively. In comparison, the ultimate tensile strength, 0.2% proof yield strength and elongation to failure of die-cast magnesium alloy AZ91D-0.4%MM at 170 oC reached to 206, 142 MPa and 26%, respectively increased by 15.7%, 10% and 30%. Proper addition of mischmetal could enhance the mechanical properties at an elevated temperature, which was attributed to the formation of Al-RE phases with high thermal stability. Hence sliding of grain boundaries and cracks could be effectively hindered by Al-RE phases.     

Modification of AZ91?Mg Alloys for High Temperature Applications

The good specific strength and specific modulus of magnesium alloys had drawn the attention of the automotive manufacturers for use in fuel efficient vehicles. Among the cast magnesium alloys, AZ91 (Mg?C9Al?C1Zn) is the most sought alloy because of its good casting properties. However, this alloy loses its strength and creep resistance properties above 120?°C due to softening of the ?? phase (Mg₁₇Al₁₂). Hence, this alloy cannot be used for making heavier engine components (power train), which require the thermal stability up to about 250?°C. The paper discusses the approach of modifying the AZ91 alloy by minor alloying additions to improve the high temperature withstanding capability without significantly affecting its casting properties. Additions of Ca to AZ91 alloy to the levels of about 0.4?wt% increased the ambient and high temperature strength of the base alloy. Additions of other minor alloying elements such as Sb, Pb, rare earths etc. can also increase the high temperature capability of the AZ91 by further modifying the ?? phase structure. The paper overviews the work carried out by the authors on the role of different alloying additions on the microstructure and mechanical properties of AZ91 magnesium alloys.     

Grain coarsening in semi-solid state and tensile mechanical properties of thixoformed AZ91D-RE

For thixoforming to be possible,the microstructure of the starting material must be non-dendritic,which can be obtained by the strain induced melt activation(SIMA)route.Based on the SIMA route,as-cast AZ91D alloy with the addition of yttrium was deformed by cyclic closed-die forging(CCDF).Microstructure evolution of CCDF formed AZ91D-RE alloy during partial remelting were investigated.Furthermore,the mechanical properties of thixoformed AZ91D-RE magnesium alloy components were also studied.The results showed that prolonged holding time resulted in grain coarsening and the improvement in degree of spheroidization.The coarsening behaviour of solid grains in the semi-solid state obeyed Ostwald ripening mechanism.The coarsening rate constant of CCDF formed AZ91D-RE during partial remelting was 324 um3/s at 550℃.The value of yield strength,ultimate tensile strength and elongation to fracture of four-pass CCDF formed AZ91D-RE magnesium alloy were 214.9,290.5 MPa and 14%,respectively.Then the four-pass CCDF formed alloys were used for thixoforming.After holding at 550℃ for 5 min,the values of yield strength,ultimate tensile strength and elongation to fracture of thixoformed component were 189.6 MPa,274.6 MPa and 12%,respectively.However,prolonged holding time led to remarkable decrease in mechanical properties of thixoformed components.     

新型复合熔剂对AZ91镁合金组织和力学性能的影响

利用金相显微镜、X-射线衍射仪、SEM、EDA、数字显微硬度计和电子万能试验机,对采用传统覆盖剂和自制覆盖剂制备的AZ91镁合金的显微组织和力学性能进行了分析。结果表明。自制覆盖剂制备的AZ91合金、Mg17Al12相得到改善,晶内出现Al4C3形核质点,晶粒得到显著细化,抗拉强度、屈服强度和延伸率都得到较大的提高。     

Study on solid solution and aging process of AZ91D magnesium alloy with cerium

The influence of Ce on solid solution and aging process of AZ91D magnesium alloy was analyzed.The results showed that the decomposition of β-Mg17Al12 phase in AZ91D magnesium alloy at 420 ℃ could be completed within 12 h,while this process in the Ce-containing alloy required more time.In subsequent aging process at 175 ℃,Ce obviously delayed the aging process of AZglD.It was inferred that the influence of Ce on process of solid solution and aging was relative to the Ce that existed in β-Mg17Al12 phase of original structure in the form of solid solution,and the interaction of the Ce and Al was an important factor to get process of solution and aging slowly.