细晶Al-Sr中间合金对AZ91D组织和性能的影响

通过真空感应炉对Al-Sr中间合金进行了铜模喷铸处理,得到了细晶Al-Sr变质剂。然后分别采用粗晶与细晶Al-Sr对AZ91D进行了变质处理。SEM、OM、XRD、拉伸试验及硬度测试结果表明:经铜模喷铸处理的Al-Sr中间合金中的第二相Al4Sr的平均尺寸从100μm减小至5μm;经Al-Sr中间合金变质的AZ91D,晶粒明显细化,力学性能明显提高,但细晶Al-Sr的变质效果更好。因此,铜模喷铸是提高Al-Sr变质效果的有效途径。     

不同冷速凝固的Mg-9Gd-0.8Al合金固溶行为及组织性能

为了探究Al元素在不同冷却速度下对Mg-9Gd合金组织细化效果及其对后续固溶处理的影响,利用铁模和铜模重力铸造制备了铸态Mg-9Gd-0.8Al合金,之后进行10~50 h的固溶处理。采用OM、SEM、TEM、EDS及XRD等方法研究了冷却速度对Mg-9Gd-0.8Al合金凝固和固溶行为及组织力学性能的影响。结果表明,铁模和铜模制备的铸态Mg-9Gd-0.8Al合金组织均由α-Mg基体、花瓣状(Mg, Al)₃Gd相、细条状Mg₅Gd相和方块状Al₂Gd相组成。铜模相比于铁模冷却速度加快,制备的合金基体晶粒和第二相显著细化,第二相体积分数总量增长幅度达56.1%。2种模具制备的合金固溶10 h后,Mg₅Gd相溶解、(Mg, Al)₃Gd相部分溶解、高熔点Al₂Gd相无变化,晶粒内析出层片状(Mg, Al)₂Gd新相,第二相总量趋于相等。固溶50 h后,(Mg, Al)₂Gd层片相回溶,残余(Mg, Al)₃Gd相发生熔断呈颗粒状,铜模制备的合金第二相颗粒比铁模的更细小。细晶强化和第二相强化使铜模制备的铸态合金性能较铁模制备的合金性能大幅提高,固溶10 h后合金屈服强度提升,伸长率基本不变。固溶处理50 h后,固溶强化、细晶强化和细小颗粒的第二相强化使铜模制备的固溶50 h态合金获得最优性能,屈服强度、抗拉强度和伸长率分别为141 MPa、234 MPa和22.4%。     

电磁搅拌工艺参数对半固态AZ91D镁合金组织的影响

研究了电磁搅拌工艺参数对半固态AZ91D合金组织的影响规律.结果表明:电磁搅拌条件下半固态AZ91D合金组织的固相颗粒为蔷薇状或粒状α-Mg,随电磁搅拌功率的增大,蔷薇状形态逐渐消失,固相颗粒形态趋于粒状和圆整;在实验范围内,随电磁搅拌电源频率的增大,半固态AZ91D合金组织中固相颗粒形态越来越圆整.这主要是由于电磁搅拌条件下半固态AZ91D合金组织的形成机理是以枝晶臂熔断为主,而在高频率下的电磁搅拌过程中,在搅拌室产生的集肤效应使得表面和中心出现宏观温度差,从而加强了固相颗粒随流场运动时的温度起伏,最终加速了枝晶的熔断.     

铜模喷铸对钐铁合金组织形貌及物相组成的影响

采用铜模喷铸技术制备钐铁合金快速凝固试样,利用薄材的非稳态导热方程计算钐铁合金在铜模内的冷却速率。借助光学显微镜、扫描电镜、能谱仪、X射线衍射仪及X射线光电子能谱仪研究了钐铁合金在氮气喷铸后快速凝固过程中的组织形貌及物相组成变化。结果表明,氮气将熔融态Sm-Fe合金喷铸到铜模内后,合金的冷却速度约为16.8 K/s;较大的冷却速率使枝晶间距明显变小,促进了合金晶粒细化,并抑制各相之间的相互扩散,合金成分更加均匀;氮化反应基本上只在喷铸试样表面进行,且生成物主要由Sm_2Fe_(17)N_x与氮的氢氧化物构成,相对含量分别为34.36%与65.64%。     

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。     

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。     

Fe基块体非晶合金的结构转变及其对力学性能的影响

通过铜模吸铸法制备了尺寸不小于2 mm的块体非晶合金Fe45Co7Cr14Mo10Y2B6C15,采用热处理的方式实现非晶合金的结构转变过程,通过组织形貌观察及热力学分析表征非晶合金的结构变化,并且就非晶合金的结构转变对压缩强度及硬度的影响进行了探讨。试验结果表明:非晶合金的结构转变受热力学和动力学因素共同影响;而晶化相的存在会对力学性能产生影响,含部分晶化相的非晶合金硬度升高,压缩强度下降。     

超细SiC颗粒对球磨制备纳米晶AZ91镁合金组织及性能的影响

通过机械球磨制备了SiC颗粒（SiC_p）增强镁基复合材料粉末（AZ91?xSiC_p,x=5%、10%、15%,体积分数）,实现了镁基体纳米化及亚微米级SiC_p在镁基体中的均匀弥散分布,研究了SiC_p对球磨后粉末微观组织的影响规律。结果表明,SiC_p第二相的引入能够促进机械球磨过程中镁基体晶粒的细化,晶粒细化程度随SiC_p体积分数的增加有所加强,同时SiC_p含量的提高对Al元素在镁基体中的固溶及其自身颗粒的细化起到抑制作用。球磨后AZ91?xSiC_p（x=5%、10%、15%）复合粉末的硬度分别为HV 166、HV 175和HV 185,强化机制为细晶强化、弥散强化、固溶强化和承载强化,计算得到AZ91?5%SiC_p复合粉末不同强化机制所引起的强化效果占比分别为86.9%、7.4%、1.8%和3.8%。     

等温退火对ZrCuAlNiCoNb非晶合金硬度和杨氏模量的影响

采用真空电弧熔炼结合水冷铜模吸铸法制备ZrCuAlNiCoNb大块非晶合金。采用XRD、AFM、SEM及纳米压痕分析手段研究等温退火对ZrCuAlNiCoNb非晶合金显微组织演变、硬度和杨氏模量的影响。结果表明,无论温度高低,退火均能使非晶合金中自由体积的数量减少。在低于玻璃化转变温度下退火,合金中自由体积数量下降,抑制了剪切带的形核,合金的硬度和杨氏模量随退火时间的增加而提高;在高于玻璃化转变温度下退火,短时间即可诱发纳米晶化,合金的硬度和杨氏模量均先增加,达到峰值后下降。ZrCuAlNiCoNb非晶合金力学性能的演变趋势是自由体积演变和纳米晶形核共同作用的结果。     

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。     

Grain refinement of AZ31 magnesium alloy by Al-Ti-C-Y master alloy

Al-Ti-C-Y master alloy was prepared by combining SHS technique and melting-casting method. The microstructure of master alloy and its grain-refining effect on AZ31 alloy were investigated by means of OM, XRD, SEM and EDS. Experimental results indicated that the prepared master alloy consisted of α-Al, TiAl3, TiC and Al3Y phases, and exhibited good grain-refining performance of AZ31 alloy. Morphology of α-Mg changed from coarse dendritic to fine equiaxed and the average grain size of α-Mg matrix reduced from the original 580 to 170 μm after adding 1.0 wt.% master alloy. The grain refining efficiency of Al-Ti-C-Y master alloy on AZ31 alloy was mainly attributed to heterogeneous nucleation of TiC particles and grain growth restriction of Al-Y compound or TiC at grain boundaries.     

Some Investigations on Friction Stir Processed Zone of AZ91 Alloy

In this study, AZ91 based hybrid nanocomposite was fabricated using mixture of TiC and alumina by friction stir processing (FSP). FSP of AZ91 was conducted with as well as without particle addition and under different cooling conditions. Distribution of nano TiC and Al₂O₃ particles in the Mg matrix was studied using SEM. Grain size analysis of the as-cast and FSP AZ91/(TiC?+?Al₂O₃) composite was done using optical microscopy. The performance of the fabricated nanocomposite was investigated using microhardness, bulk hardness and scratch tests. Microhardness testing was done at 50?gf load and bulk hardness at 5?Kgf load. Scratch test was performed at 2 and 5?N normal load values on a universal tribometer using Rockwell indentor. AZ91/(TiC?+?Al₂O₃) composite exhibited improved mechanical properties.     

Effect of Y Addition on Microstructure and Constituent Phases of Al-Ti-C Master Alloy

Al-Ti-C master alloy was prepared by SHS (Self-propagating High temperature Synthesis)-melting technique. Effect of yttrium addition level on the microstructures of the master alloy was studied by XRD, SEM and EDS. The experimental results show that the addition of 1.0%Y is beneficial to the formation of TiC particles; Al-Ti-C-1.0Y consists of rod-like and blocky TiAl3, TiC, Al3Y and α-Al matrix. Y is found around TiC particles in Al-Ti-C-0.5Y master alloy while blocky (AlTiY) phase appears in Al-Ti-C-1.0Y master alloy. Al3Y with dendritic morphology and small blocky Al2Y except for TiC are found in Al-Ti-C-2-0Y master alloy.     

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…     

AZ91D铸造镁合金交流脉冲双极微弧电沉积陶瓷膜

利用交流脉冲方法在AZ91D铸造镁合金表面成功实现阴、阳极微弧电沉积陶瓷膜,并使用SEM和XRD等手段对陶瓷膜的厚度、组织形貌、成分、结构和耐蚀性作了相应研究分析.结果表明,应用交流脉冲方法不仅能够在AZ91D铸造镁合金上实现阴、阳双极微弧电沉积陶瓷膜,同时在阴、阳极陶瓷膜中电沉积有稀土元素Ce.通过比较动电位扫描极化曲线和交流阻抗分析发现阴、阳极微弧氧化处理后AZ91D镁合金的耐蚀性得到显著提高.     

稀土元素铈对镁合金AZ91D显微组织和力学性能的影响

利用光学显微镜、X射线衍射和扫描电镜等分析研究含铈镁合金AZ91D（0．25％Ce、0．7％Ce、0．95％Ce）的显微组织,并对其力学性能进行了测试,同时与不含铈镁合金AZ91D进行了比较。结果表明,加入一定量Ce后的镁合金AZ91D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能提高镁合金AZ91D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镁合金晶粒细化效果和综合力学性能比较理想。     

Effect of Neodymium on As-Cast Microstructure and Mechanical Properties of AZ31 Wrought Alloy

Nd in the form of powder or intermediate alloy was added to AZ31 wrought alloy. The as-obtained alloy was characterized and tested with respect to its microstructure and mechanical properties. The relationship between the microstructure, mechanical properties and tensile fracture mechanism were discussed, with relevant alloys as reference for comparison. Experimental results show that the same quantity of Nd was added into AZ31 in powder form or in intermediate alloy, the absorption rate of Nd reached only 10.8% for the former case and as high as 95% for the later case. Pure Nd powder was added, no new compound was detected, but it served as reductant and purified alloy melt, resulting in improving the tensile strength while Nd was added into AZ31 as Mg-Nd intermediate alloy. The compound Al2Nd and Mg12 Nd were formed in magnesium alloy, which were distributed in the matrix in the shapes of strip and particle, evidently refined the as-cast structure. The as-cast tensile strength (228MPa) of adding pure Nd powder approximated to the figure (245MPa) of adding Mg-Nd intermediate alloy. The tensile fracture mchanism of as-cast AZ31 transformed from cleavage fracture into quasi-cleavage fracture.     

钪对AZ91合金组织和性能的影响

研究钪在AZ91合金中的相组成、形貌及其对合金组织和性能的影响。结果表明,钪在合金中生成Al3Sc高温耐热相,细化了枝晶组织。钪添加量为0.6%时,室温和200℃的抗拉强度分别为265.4MPa和161.1MPa。钪可显著降低合金自腐蚀电流密度,但腐蚀电位只有轻微增加。