粉末烧结对Mg-Sc合金微观组织和力学性能的影响

在惰性气氛下，经500℃烧结2 h和300℃挤压制得镁钪合金，并对其进行微观组织观察和力学性能测试。结果表明：粉末烧结镁钪合金的相组成主要为基体Mg相，未发现Mg-Sc相生成。在粉末烧结过程中，钪元素在镁基体中发生扩散，明显改善界面结合形式，提高了镁钪界面的结合性。当钪质量分数为1.0%时，镁钪合金的伸长率达到10.37%，提高了61%。在拉伸试样断口处发现大量韧窝存在，说明烧结处理可明显提高镁钪合金的韧性。     

放电等离子烧结快速制备高钪含量铝钪合金

采用放电等离子烧结技术制备高钪含量Al-Sc合金,利用扫描电子显微镜、能谱仪和X射线衍射仪等设备对球磨前后Al-Sc合金粉末的形貌、相组成以及不同温度快速烧结样品的显微组织结构进行观察和分析,研究烧结温度对Al-Sc合金显微组织的影响。结果表明:球磨后粉末的形状较规则,其颗粒尺寸为25~45mm,并初步实现了机械合金化,除Al、Sc相以外,有少量Al3Sc和AlSc2相生成。放电等离子烧结可实现高钪含量铝钪合金的快速致密化,成功制备出钪含量30%(质量分数)的铝钪合金,通过调整烧结工艺参数,烧结样品的相对密度可达92.19%;当烧结温度高于500℃时,所得样品致密,无孔洞,且无明显晶界;随着烧结温度的提高,Sc相与第二相融合,形成Al3Sc、AlSc2等第二相,存在于合金中,且Al3Sc相呈现逐渐增强的趋势。     

LiF-ScF3-ScCl3体系熔盐电解制备铝镁钪合金

以氧化钪为原料、液态铝镁合金作阴极,在氟化锂-氟化钪-氯化钪(LiF-ScF3-ScCl3)体系中通过熔盐电解制备铝镁钪(Al-Mg-Sc)合金.针对LiF-ScF3-ScCl3体系,实验考查了温度、熔盐组成、电流强度和电解时间等因素的影响.结果表明,熔盐电解可制备出钪含量在2%～10%、镁含量0.2%的铝镁钪合金.采用XRD,SEM和电子能谱分析等方法对合金样品进行了表征,结果表明,合金金相分为两相,连续相为铝基,间断相为ScAl3.     

加钪对Al-Zn-Mg-Cu-Zr合金组织性能的影响

本文研究了微量钪对Al-Zn-Mg-Cu-Zr合金组织及性能的影响。钪在铝合金中主要以两种形式的化合物存在，一种是合金凝固时从熔体中析出的一次Al2(Sc，Zr)相，另一种是铸锭均匀化时析出的二次Al2(Sc，Zr)相。前者是αa(Al)晶粒细化剂，可有效细化铸态晶粒；后者可强烈牵制晶粒内位错及亚晶界，有效阻止热轧、退火或固溶处理过程中的再结晶。钪是产生强烈析出强化的合金元素，同不加钪的铝合金相比，含0．30％Sc的Al-Zn-Mg-Cu-Zr合金的抗拉强度和延性显著提高。     

钪对7005铝合金组织性能的影响

采用金相、透射电镜、扫描电镜、拉伸试验等测试手段，研究了不同含量的稀土元素钪对７００５铝合金组织性能的影响。加入适量钪合金化可以明显细化合金组织，改变主要强化相η相的尺寸、形态、分布，减小晶界无沉淀带宽度，可以明显提高合金强度、塑性以及高温稳定性，这是合金中析出了与铝在体完全共格的Ａｌ３Ｓｃ（ｆｃｃ，α＝０．４１ｍｍ）质点所致。     

一种单晶高温合金的组织和持久性能

研究了一种第二代单晶高温合金的显微组织和不同条件下的持久性能.研究结果表明合金铸态组织由γ相、γ′相和共晶相组成.完全热处理后,无共晶和初熔,γ′相立方化较好.合金不同条件下持久性能良好.在760 ℃/800 MPa条件下持久断裂为类解理断裂,而合金980 ℃/250 MPa、1 100 ℃/140 MPa的高温持久断裂显示出韧窝断裂特征.持久断裂组织分析表明,在760 ℃/800 MPa条件下,γ′相仍保持立方状.在980 ℃/250 MPa条件下,γ′相发生筏排化.在1 100 ℃/140 MPa条件下,γ′相筏排化更严重.      

锆和钪对Al-Mg铸造合金组织和力学性能的影响

通过金相显微镜、拉伸力学性能测试、XRD等手段研究了在铸造Al-Mg合金中添加不同含量的钪和锆后合金的铸态组织。结果表明,合金添加钪和锆后,明显减小了枝晶网胞尺寸,细化了晶粒。当锆和钪的添加量分别为0.2%、0.4%时,铸造Al-Mg合金组织具有良好的综合性能。     

钪在铝合金中的作用

介绍了目前Al－Sc合金的研究现状,总结了添加微量钪对铝合金组织和性能的影响,钪在铝合金中可以起到变质剂的作用而使合金的晶粒细化,钪的加入对合金力学性能,焊接性能和耐蚀性能的提高具有重要影响。     

复合添加Sc对Al-6.2Zn-2.5Mg合金板材焊接性能与组织的影响

文章利用显微硬度试验、显微组织观察等手段,研究了复合添加Sc元素对Al-6.2Zn-2.5Mg合金板材氩弧焊焊接性能与组织的影响规律。试验结果表明,带余高的含钪合金板材较不含钪的合金板材焊接系数提高了9.2%,具有较好的焊接性能;合金板材焊接接头中心处硬度值最低,并沿中心往基材方向,呈先升高后降低再增高的趋势,且硬度以焊缝为中心呈近似对称;且含钪合金板材的接头晶粒组织较不含钪合金板材的组织要细小得多。在焊接过程中,含Sc合金板材组织中形成的Al3Sc粒子提高了合金板材的整体焊接性能。     

Sc在铝合金中的微合金化作用机理

综述国内外含钪铝合金的研究历史与现状,论述钪的细化合金晶粒、提高再结晶温度、改善合金力学性能、提高抗腐蚀性能以及改善焊接性能的作用机理,重点介绍第一性原理、嵌入原子势模型和经验电子理论对含钪铝合金形成焓与结合能等热力学性质计算以及相稳定性研究的最新进展,最后论述钪对改善铝铜系合金综合性能的作用机制。     

钇对AZ91合金组织和性能的影响

研究微量稀土钇对AZ91合金微观组织、力学性能、腐蚀性能的影响,考察钇在合金中所形成的稀土相组成和形貌。结果表明,钇在AZ91合金中生成Al4MgY相,可起非均质形核作用,减少二次枝晶间距,细化枝晶组织。加入钇后,合金腐蚀性能得到明显改善,由严重的全面腐蚀向只有表面部分位置有轻微点蚀的均匀腐蚀转变。当钇加入量为1.25%时,合金的室温和高温力学性能最好,分别为264.8MPa和164.8MPa。     

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 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.     

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.     

不同加热轧制AZ91镁合金带材数值模拟及试验验证

利用有限元法研究了热辊热带(HSR-HR)、热辊冷带(NSR-HR)和冷辊热带(HSR-NR)3种不同加热方式下AZ91镁合金轧制过程热-力行为,并进行了大压下率热辊冷带工艺试验和组织性能分析。结果表明,HSR-HR、NSR-HR及HSR-NR 3种加热轧制方式的应力三轴度依次增大,中性点附近应力状态软性系数依次减小。热辊冷带方式通过热量传递兼具变形和退火双重作用, 确保了轧件变形温度和变形均匀性,有利于镁合金塑性变形极限提升和轧制过程裂纹愈合。辊面温度达300 ℃以上时,3道次轧后镁合金带材宏观形貌较好,组织发生了充分的动态再结晶,晶粒细化明显,有效提高了镁合金室温塑性和强度。辊面温度为350 ℃和轧制压下率为67%条件下,轧后带材抗拉强度和伸长率分别达312 MPa和32.3%。     

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.     

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。     

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。     

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…     

Mg-Gd-Y与AZ31两种变形镁合金的冲击波响应

利用平行平面正碰撞方法产生的冲击波对Mg-Gd-Y与AZ31两种典型变形镁合金加载,并对回收后的材料进行准静态压缩实验,采用金相显微镜和透射电子显微镜进行微观组织分析。冲击波加载后,原始固溶态Mg-Gd-Y合金的屈服强度增加了21 MPa,而时效峰状态合金的屈服强度仅增加4 MPa,时效处理后产生的析出相β’使合金的屈服强度增加幅度明显减少;然而,AZ31镁合金的屈服强度增加了40 MPa。Mg-Gd-Y与AZ31镁合金的冲击波加载后力学响应的差异取决于冲击波过程中两者所具有的不同变形机制,冲击波变形后Mg-Gd-Y合金中的孪晶体积分数非常少,其变形机制以位错滑移为主。相比之下,冲击波加载后的AZ31合金中产生了大量孪晶,孪生是该合金的一种重要变形机制。孪晶界在后续再加载过程中成为位错滑移的障碍,从而导致AZ31镁合金表现出更为显著的冲击波强化效果。