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1.
通过金相观测、断口扫描和力学性能测试等实验,研究了宽幅AZ31B镁合金铸轧板的组织分布,及其对板带边裂和力学性能的影响。结果表明:AZ31B镁合金铸轧板的组织主要由α-Mg基体、析出相β-Mg17Al12相及α+β离异共晶组成,呈树枝晶形貌;β-Mg17Al12相在AZ31B镁合金铸轧板坯的表层及边部主要分布于晶界处且密度较大、构成网状,而在板坯的心部和中部呈球状弥散于α-Mg基体中,构成层片状;在板坯边部枝晶间低熔点的共晶相及晶界上的β-Mg17Al12相易成为裂纹源,并沿晶向外扩展,是铸轧过程中产生裂纹的主要原因;试样拉伸断口呈脆性解理断裂的特征,其力学性能呈明显的各向异性。  相似文献   

2.
用金相显微镜、能量色散谱仪(EDS)和X射线衍射仪(XRD)研究了稀土元素Ce对AZ91D镁合金铸态组织的影响.结果表明,Ce对AZ91D镁合金具有明显的变质效果,加入0.4%Ce后,α-Mg树枝晶变化不明显,晶界上的β-Mg17Al12相呈断续网状分布;加入0.8%Ce后,合金晶界上的离异共晶β相基本上断裂成骨骼状,转变为颗粒状且分布比较均匀;加入1.2%稀土Ce后,枝晶变细,共晶β相完全变为颗粒相,弥散分布于晶界处.微结构分析发现,组织中出现了分布于晶界处的杆状Al10Ce2Mn7化合物.  相似文献   

3.
ZM5镁合金TIG焊接接头组织与力学性能   总被引:1,自引:0,他引:1  
采用TIG焊对ZM5镁合金进行焊接,利用光学显微镜、显微硬度仪和拉伸试验机对ZM5镁合金接头的组织特征和力学性能进行研究。结果表明:ZM5合金TIG焊接接头是由热影响区、部分重熔区和焊缝组成。热影响区组织是由初生α-Mg相基体和主要分布在晶界上的α-Mg+β-Mg17Al12共晶相组成;部分重熔区中共晶相不仅大量析出在晶界上,在晶内也呈现出较均匀的弥散析出,而且其β-Mg17Al12相出现显著长大;焊缝组织则是典型的树枝晶形貌,枝晶为初生α-Mg相,枝晶间是α+β共晶相。组织形貌的差异导致接头各区域有着不同的显微硬度,也使得接头的抗拉强度和塑性都低于母材。  相似文献   

4.
旨在优化AZ91镁合金凝固组织,通过OM和XRD设备研究了不同离心压力和冷却速度对AZ91镁合金凝固组织演变的影响,结果表明,随着离心压力的增大,合金晶粒尺寸细化,第二相β(Mg12Al17)析出量减少,不保温试样,β相形态由粗大连续网状向细小断续状转变,保温试样,β相为粒状弥散分布晶内,压力增大,颗粒数量减小,粒径细化.同等凝固压力下,增大冷速,一次β相析出量增多,二次β相析出量减少.XRD分析表明,增大离心压力β相峰值略微减弱,α-Mg的晶格常数减小.  相似文献   

5.
用石膏型熔模铸造技术,成功制备了AZ91镁合金铸件.用金相显微镜(OM)、扫描电镜(SEM)、能谱(EDS)以及电子万能实验机等,研究了AZ91镁合金铸态及T4热处理态的显微组织演变和力学性能.结果表明,分布在铸态AZ91镁合金晶界的网状β-Mg17Al12相在T4热处理过程中逐渐溶解,铸态和T4热处理态中均存在大量的A18Mn5化合物,T4处理后,其力学性能显著提高.  相似文献   

6.
MgCO3在AZ31镁合金中的细化效果及机理   总被引:1,自引:0,他引:1  
为改善AZ31镁合金铸态组织,用MgCO3对其进行细化,采用扫描电子显微镜、X射线衍射仪和金相显微镜研究了细化工艺参数对AZ31镁合金显微组织及其物相组成的影响.结果表明:在AZ31中添加质量分数为0.6%的MgCO3,于760℃保温10 min细化效果最佳,α-Mg晶粒的尺寸由基体合金的570μm降至100μm,降幅约82.5%.少量多次添加MgCO3的细化效果明显优于单次添加MgCO3的细化效果.研究认为,细化机理是MgCO3反应后生成的部分Al4C3质点作为异质核心细化晶粒,多余的Al4C3质点钉扎晶界阻碍晶粒长大.Al元素随固/液界面前沿被快速推至晶界,生成沿晶界生长的β-Mg17Al12相,起到进一步固定晶界的作用.合金元素的分布均有改变.  相似文献   

7.
许楠  沈骏  刘辉 《功能材料》2011,42(4):682-684
通过对AZ系镁合金钨极氩弧焊(TIG)焊接接头进行固溶时效处理,研究其显微组织和显微硬度的变化.结果表明,在时效初始阶段(0~10h),熔合区中Al和Zn元素扩散速度和β-Mg17(Al,Zn)12的体积分数增加较快,其显微硬度随之增加较快.随着时效时间的延长,熔合区中的βMg17(Al,Zn)12的析出逐渐达到饱和,...  相似文献   

8.
Ca对AZ91显微组织及力学性能的影响   总被引:26,自引:0,他引:26  
用气体保护法制备了含的合金,研究了对合金显微组织和力学性能的影响。结果表明,Ca能显著细化AZ91合金铸态和时效态的组织,改善了铸态组织形态。Ca的加入未形成新相或沉淀物,而是溶入β-Mg17Al12相中,并提高了β-Mg17Al12相的热稳定性。Ca的加入可以明显提高AZ91合金室温及高温下的拉伸性能。  相似文献   

9.
在CO2/SF6气氛保护下,采用压铸的方法将-200目的Al63Cu25Fe12准晶粉末注入到熔融的AZ91镁合金中,于720℃和一定的压力下保压30min,制备了新型的(Al63Cu25Fe12)p/AZ91镁基复合材料.结果表明,在复合过程中,准晶相分解出的自由Cu向基体扩散并与基体中的Al发生反应,生成的金属间化合物分布在准晶颗粒周围,同时Mg向颗粒中浸渗填充到颗粒的孔隙中;复合材料具有不同于基体镁合金的固溶时效特征,需要更长的时间才能达到时效峰值;复合材料经过热挤压和热处理后的力学性能显著提高,抗拉强度从AZ91铸态材料的189.54MPa提高到359.38MPa,但塑性有所降低.  相似文献   

10.
Mg-9Al-1Zn-(0-0.6)Sr镁合金铸态组织及晶粒细化研究   总被引:1,自引:0,他引:1  
对含Sr(0.05%~0.6%)AZ91铸态镁合金组织进行了观察,并且采用"边-边匹配"模型研究了其细化机制。结果表明,微量Sr对AZ91铸态组织有明显的晶粒细化效果,Sr含量为0.05%时细化效果最为显著。通过"边-边匹配"模型计算,得到[021]Al4Sr∥[1-1 0]Mg17Al12,(200)Al4Sr∥(332)Mg17Al12,表明微量Sr对AZ91镁合金铸态晶粒细化主要是Al4Sr相为Mg17Al12相的形成提供有效的异质形核核心,从而加速Mg17Al12相对α-Mg枝晶长大的阻碍作用。  相似文献   

11.
Under the cold-chamber high pressure die casting (HPDC) process, samples were produced with AM60B magnesium alloy to investigate the microstructure characteristics of the eutectics, especially focusing on the constitution, morphology and distribution of the eutectics over cross section of the castings. Attentions were also paid to study the effect of heat treatment on the eutectics in the die castings. Based on experimental analysis using optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS), it was determined that fully divorced eutectics consisting of α-Mg and β-Mg17Al12 appeared at the grain boundary of the primary α-Mg in the as-cast microstructure. Islands and networks of β-Mg17Al12 phase were observed in the central region of the castings, while the β-Mg17Al12 phase revealed a more dispersed and granular morphology on the surface layer. The two phases ratio β/α in the central region of the castings was approximately 10%, which was higher than that on the surface layer. Besides, the defect bands contained a higher percentage of the eutectics than the adjacent regions. After aging treatment (T6), only α-Mg phase was detected by XRD in the AM60B magnesium alloy, though a small amount of precipitated β-Mg17Al12 phase was observed at the grain boundary. In contrast to the microstructure of die cast AZ91D magnesium alloy under the same T6 heat treatment, no discontinuous precipitation of the β-Mg17Al12 phase was observed in AM60B magnesium alloy die castings.  相似文献   

12.
锑合金化对镁铝基合金力学性能的改善作用   总被引:20,自引:0,他引:20  
研究了锑合金化对镁铝合金Mg-9Al-0.8Zn(AZ91)显微组织和力学性能的影响,结果表明,锑低合金化可以显著提高AZ91合金在从室温至200℃区间内的拉伸屈服强度,用扫描电镜和透射电镜详细分析了试样形变前后的显微组织及其变化,发现在AZ91合金中加入0.1wt%-1.0wt%的Sb后,合金的显微组织得到明显细化,Sb在AZ91合金中的存在方式主要有两种,(1)固溶入β-Mg17Al12相,(2)以Mg3Sb2形式析出,该颗粒具有六方结构(D52型),有很高的热稳定性,可以作为α-Mg非自发形的衬底,在此基础上探讨了Sb合金的化提高镁铝合金性能的机理,室温下主要是细化基体昌粒产生的昌界强化机制,高温下则主要通过自生相(Mg3Sb2)粒子的弥散强化机制。  相似文献   

13.
陈鹏  马国红  平奇文 《材料导报》2017,31(20):82-86
研究了碳化硅(SiC)颗粒涂覆量对2mm厚AZ31B镁合金双电极气体保护焊DE-GMAW焊缝的宏观形貌、显微组织和力学性能的影响。利用光学显微镜、扫描电镜和X射线衍射分析技术(XRD)对接头的显微组织、相及相的成分进行分析。同时采用维氏硬度试验计和万能试验机对焊接接头的显微硬度和抗拉强度分别进行测量。结果表明,随着SiC涂覆量的增加,焊接接头熔深和深宽比先增大后减小。XRD测试结果显示,SiC的添加并不改变焊缝中相的组成,焊缝由α-Mg和β-Mg_(17)Al_(12)组成。SiC可以细化α-Mg晶粒,打断焊缝中β-Mg_(17)Al_(12)相,起到弥散强化的效果。但SiC涂覆量达到一定值后,随着SiC涂覆量的继续增加,α-Mg晶粒粗化,β-Mg_(17)Al_(12)相的弥散强化作用不再增加。焊接接头的显微硬度和抗拉强度随着SiC涂覆量的增加先增大后减小。  相似文献   

14.
杨湘杰  郑彬  付亮华  杨颜 《材料工程》2022,50(7):139-148
采用控制变量法研究单一稀土Y和复合稀土Y,Sm元素对AZ91D镁合金微观组织与力学性能的影响,分析稀土元素对AZ91D合金的细化机理。结果表明:复合添加稀土Y和Sm对AZ91D合金的作用效果明显好于单一添加稀土Y对AZ91D合金的作用效果,添加Y和Sm后,生成了块状相Al2Y相和针状相Al2Sm相,可以作为α-Mg的有效异质形核点。当加入量为0.8%(质量分数,下同)Y+1.0% Sm时,α-Mg晶粒尺寸最为细小,分布最为均匀,其合金的硬度、抗拉强度及伸长率分别为67.42HV,153.37 MPa和3.62%,改善了铸态AZ91D合金的室温力学性能,但是超过这个最佳添加量后,合金的室温力学性能开始下降。  相似文献   

15.
采用Nd:YAG毫秒脉冲激光器,在高纯氩气保护下扫描AZ91D镁合金样品,采用X射线衍射仪(XRD),光学显微镜,扫描电镜(SEM),原子力显微镜(AFM)等对处理后镁合金表面形貌、组织、成分进行研究。使用模拟改性体液和质量分数为3.5%的NaCl溶液对实验样品进行腐蚀,观察腐蚀表面并计算材料腐蚀率。结果表明:在相同腐蚀时间下,与未被处理样品相比,激光处理后镁合金由于其显微组织中细化的α-Mg相与β-Mg_(17)Al_(12)相,及选择性气化现象和基体合金化学成分共同导致表面Al元素富集提高了表层的抗腐蚀性能;通过测算激光熔化区枝晶晶胞尺寸与冷却速率的关系得到其凝固方程。  相似文献   

16.
The effects of 2 wt.% rare earth element addition on the microstructure evolution, thermal stability and shear strength of AZ91 alloy were investigated in the as-cast and annealed conditions. The as-cast structure of AZ91 consists of α-Mg matrix and the β-Mg17Al12 intermetallic phase. Due to the low thermal stability of this phase, the strength of AZ91 significantly decreased as the temperature increased. The addition of rare earth elements refined the microstructure and improved both thermal stability and high-temperature mechanical properties of AZ91. This was documented by the retention of the initial fine microstructure and ultimate shear strength (USS) of the rare earth elements-containing material after long-term annealing at 420 °C. The improved stability and strength are attributed to the reduction in the volume fraction of β-Mg17Al12 and retention of the thermally stable Al11RE3 intermetallic particles which can hinder grain growth during the annealing process. This behavior is in contrast to that of the base material which developed a coarse grain structure with decreased strength caused by the dissolution of β-Mg17Al12 after exposure to high temperature.  相似文献   

17.
热挤压AZ31镁合金的组织结构与蠕变行为   总被引:1,自引:1,他引:0  
通过对热挤压态AZ31镁合金进行组织形貌观察、内摩擦应力测定及蠕变性能测试,研究了热挤压AZ31合金的组织结构和蠕变行为.结果表明:热挤压AZ31镁合金的组织具有带状结构特征,并沿轧制方向分布,且有β-Mg17Al12相在合金中弥散析出.蠕变期间,位错运动的内摩擦力有较强的温度敏感性,随温度增加,内应力值明显降低,致使合金具有较高的蠕变速率.合金在蠕变期间,大量位错的形成与运动是蠕变初期的变形机制;蠕变稳态阶段,高密度位错逐渐束集形成位错胞,进一步发生蠕变期间的动态再结晶.随裂纹在晶界处萌生使蠕变进入第三阶段,而裂纹沿晶界韧性撕裂扩展是合金的蠕变断裂机制.  相似文献   

18.
In order to get improved mechanical properties of die-cast AZ91 alloy under elevated temperatures, Ca element was added as a cost-effective alloying constituent. It appeared that minor Ca addition less than 0.5 wt% would result in no apparent change in microstructure, but the tensile strength at elevated temperatures was improved considerably. When increasing Ca addition to more than 1.0 wt%, Al2Ca phase will precipitate during solidification, no Mg2Ca phase was discovered. Homogeneous microstructure and high temperature stability in tensile strength of die-cast AZ91 alloy with Ca addition was mainly attributed to the precipitation of Al2Ca phase, which considerably refined the bulky β-Mg17Al12 phase distributed originally at the grain boundaries of die-cast AZ91 alloy with no Ca addition. The priority of Al2Ca phase compared to Mg2Ca phase in precipitation sequence was verified by first-principle calculation of their cohesive energy and formation enthalpy, and can also be associated with more bounding electrons between Al and Ca atoms.  相似文献   

19.
The ageing behavior of Mg-xAl-Zn alloys with a variation of AI contents (x=3,5,7,9 and 11 wt pct) were investigated.Solid solution treatment and artificial ageing were carried out at 693 and 493 K,respectively. After the solid solution treatment,β-Mg-(17)Al-(12) was resolved to theα-Mg matrix in the specimens which contained Al up to 9 wt pct and partially resolved in the specimen of 11 wt pct Al.During ageing,theβ- Mg-(17)Al-(12) phase was precipitated at the grain boundary in the form of discontinuous precipitation and grown into the matrix.The volume fraction ofβ-phase was increased with the Al contents.Tensile strength increased with the volume fraction of precipitatedβ-phase,which was believed to strengthen the matrix.  相似文献   

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