Zn掺杂对镁锂合金物相结构及力学性能影响的研究

从Mg-5Li-0.5Y出发,制备了不同Zn掺杂比例(0,0.3%,0.5%,1.0%)(质量分数)的镁锂合金材料,研究了Zn掺杂比例对镁锂合金微观结构和力学性能的影响。通过XRD、SEM和力学性能测试等对不同Zn掺杂比例的镁锂合金的物相结构、断面相貌和拉伸性能等进行了表征。结果表明,合金主要由α-Mg和β-Li相组成,为典型的α+β双相结构,随着Zn的掺入,合金中出现了Mg_(12)ZnY的衍射峰;所有合金的晶粒都比较均匀细密,尺寸约在5μm左右,Zn的加入改善了合金的微观结构,使晶粒更细化,晶界更光滑,且改善了α-Mg相和β-Li相的分布;随着Zn含量的增加,合金的抗拉强度和屈服强度都呈现出先增大后降低的趋势,而断裂延伸率呈现出逐渐上升的趋势。当Zn的含量为0.5%(质量分数)时,合金的抗拉强度和屈服强度达到最大值,分别为136和125 MPa;当Zn的含量为1.0%(质量分数)时,合金的断裂延伸率达到最大值,为10.7%;Zn的掺入导致合金的晶粒尺寸出现了明显的细化,合金断裂方式为韧性断裂。当Zn的含量为0.5wt%时,合金的力学性能改善效果最好,而继续增加Zn含量,合金断口处颗粒物增多,导致晶体中出现了较多的缺陷和杂质,使得合金的力学性能下降。     

冷却速率对Mg-4.4Zn-0.3Zr-0.4Y变形镁合金组织和性能的影响

通过水冷和空冷两种冷却方式制备成分相同的Mg-4.4Zn-0.3Zr-0.4Y(质量分数/%,下同)铸态合金,挤压变形后进行时效处理,研究不同熔体冷却速率对挤压态和时效态合金组织性能的影响。结果表明:通过水冷冷却可以显著细化铸态组织,促进I相(Mg3YZn6)的生成,并抑制W相(Mg3Y2Zn3)的形核;由于初始组织不同,水冷和空冷两种冷却方式铸造的Mg-4.4Zn-0.3Zr-0.4Y合金经过挤压变形后,抗拉强度分别达到327MPa和306MPa,伸长率分别达到14.8%和10.0%;时效处理后,合金的晶粒尺寸和织构强度变化很小,析出的MgZn相和MgZn2相含量成为影响时效态合金性能的主要因素;时效处理挤压态水冷冷却铸造合金的屈服强度和抗拉强度分别达到330MPa和348MPa,伸长率为14.4%,与时效前相比略有减小;时效处理挤压态空冷铸造合金的屈服强度和抗拉强度增大至344MPa和359MPa,伸长率降至8.6%。     

医用Mg-Zn-Ca-Mn合金在PBS模拟体液中的腐蚀行为

利用真空感应熔炼,采用金属模浇铸制备了Mg(100-x-y-z)-Znx-Cay-Mnz四元合金。使用光学显微镜、X射线衍射仪、扫描电镜及能谱仪对合金进行分析和表征。探讨了合金在PBS模拟体液中的腐蚀行为。结果表明,Ca、Zn及Mn原子的复合加入可显著细化合金的铸态显微组织;镁合金的腐蚀发生于晶粒内部,至晶界处终止;当加入2.0%的Zn和0.5%的Ca时,铸态合金的抗腐蚀性能最佳(平均腐蚀速率为0.77mm/a);当Zn、Ca含量均大于1%时,固溶时效态合金的腐蚀速率下降为铸态的1/2～1/4,表现出优异的耐蚀性;固溶时效处理可有效减少Mg2Ca相的体积分数,改善其分布,提高合金的耐蚀性能。     

Bi对挤压态AZ61镁合金组织和力学性能影响

研究了添加Bi元素对AZ61镁合金铸态、固溶态和挤压态组织和力学性能的影响。实验结果表明,向合金中加入Bi后,铸态合金基体中析出了片状和颗粒状的Mg3Bi2相,挤压态合金的组织得到了细化。当加入2%(质量分数)Bi后,挤压态合金的屈服强度和抗拉强度达到最大值,分别为239.4和322.6 MPa。随着Bi含量的进一步增加,粗大的Mg3Bi2相显著增多,加载时割裂基体,导致力学性能降低。     

Mg-Y-Nd-Zr镁合金焊接接头的显微组织与力学性能研究

目的研究Mg-Y-Nd-Zr镁合金焊接接头显微组织和力学性能。方法采用钨极氩弧焊工艺制备Mg-Y-Nd-Zr合金焊接接头,采用金相显微镜、扫描电子显微镜观察焊接接头显微组织,采用能谱测试主要合金元素含量,采用电子万能实验机测试焊接接头的力学性能,采用维氏硬度计测试焊接接头的硬度。结果Mg-Y-Nd-Zr合金母材、焊缝区与热影响区平均晶粒尺寸分别为80, 30, 95μm。焊接接头的抗拉强度、屈服强度和断后伸长率分别为295 MPa, 188 MPa和3.0%。结论 Mg-Y-Nd-Zr合金母材、焊缝和热影响区晶粒均为等轴晶,与母材相比,热影响区未发生晶粒粗化,焊缝区晶粒明显细化,析出相Mg24Y5增多。Mg-Y-Nd-Zr合金焊接接头经525℃×12 h固溶+225℃×12 h时效处理后,各区域的硬度差异不大。抗拉强度达到母材的93%,断后伸长率达到母材的67%。     

LPSO相增强Mg-6Gd-4Y-xZn合金的组织与力学性能

制备了3种LPSO相增强Mg-6Gd-4Y-xZn(x=1,2,3)(%,质量分数,下同)四元镁合金,研究了不同Zn含量对合金显微组织和室温力学性能的影响,并探讨了合金中LPSO相的形成与演变过程及其对合金的强化机制。研究结果表明,Mg-6Gd-4Y-3Zn合金的铸态组织主要由α-Mg和18R长周期结构相Mg12Y1Zn1相组成。若降低合金中的Zn含量,显微组织中会出现Mg24(GdYZn)5。3种合金的退火组织均由α-Mg、18R-LPSO和14H-LPSO相组成,且随着Zn含量的增加,合金中18R-LPSO相的体积分数增加且基体中14H-LPSO相的层片变粗。挤压态合金在T6和T5处理的过程中均发生了β'沉淀。随着Zn含量增加,合金Mg-6Gd-4Y-xZn(包括挤压态和时效态)在常温下的抗拉强度降低。显微组织中18R-LPSO相、细小弥散分布的14H-LPSO相和β'沉淀相共存方能实现理想的强化效果。     

热挤压Mg-3Sn-1Zn-xCu合金的显微组织与力学性能

研究了添加Cu对热挤压Mg-3Sn-1Zn合金显微组织和力学性能的影响。结果表明:添加少量Cu能显著细化热挤压Mg-3Sn-1Zn合金晶粒,同时在合金中形成具有高热稳定性的CuMgZn相,提高了合金的室温及高温强度和塑性。当Cu含量为0.5%时,热挤压Mg-3Sn-1Zn-0.5Cu合金的晶粒最细,为2.8 μm;其强度和塑性最高,室温屈服强度为241 MPa,伸长率为20.3%,150 ℃时屈服强度为128 MPa,室温拉伸力学性能优于挤压态AZ31B合金,高温强度优于铸态AE42合金。     

稀土元素Nd对Mg-Zn-Y合金组织结构和力学性能的影响

通过制备Mg-6Zn-1.5Y-0.8Zr-xNd(x=0、1、2、3、4)系列合金,研究了稀土元素Nd对Mg-6Zn-1.5Y-0.8Zr合金组织结构和力学性能的影响。通过金相显微镜、扫描电镜、EDS、XRD等手段,观察和分析了合金的微观形貌和组织结构,测量了合金抗拉强度、屈服强度和伸长率等力学性能。结果表明:合金中添加稀土元素Nd后晶粒明显细化,随着Nd元素含量的增加,晶粒细化效果更为明显;通过XRD分析可知,添加Nd元素后,合金中并没有出现新的含Nd的物相;扫描电镜和EDS分析表明,合金中加入的Nd置换了部分Y,形成了Mg3(NdY)2Zn3、Mg3-(NdY)Zn6的相结构,Nd元素对Y的置换主要出现在Mg3(NdY)2Zn3结构中,在Mg3(NdY)Zn6相结构中出现较少;力学性能测试结果表明,随着Nd含量增多,合金晶粒细化,细晶强化作用明显,合金屈服强度逐渐增大,而抗拉强度和伸长率在Nd含量为3%(质量分数)时达到最大,比未添加Nd元素时提高约25%以上。     

Mg和Si含量对一种低频电磁铸造新型高强Al-Mg-Si-Cu合金组织性能的影响

结合金相组织观察及能谱分析、DSC热差分析、JMat Pro 5.0软件计算和室温力学性能测试,研究低频电磁铸造新型高强Al-Mg-Si-Cu合金铸态、挤压态和T6态的组织性能。结果表明,该新型合金系的均匀化温度和固溶温度可分别确定为540℃和550℃。Mg_2Si强化相能显著细化合金铸态组织且细化程度随其含量增大递增,而过量Si或过量Mg均能减弱细化剂和Mg_2Si相对合金铸态组织的细化作用。Mg的过量添加不会降低合金强度但可提高其延伸率至19%以上。该新型Al-Mg-Si-Cu合金中,当Mg质量分数为1.60%、Si质量分数为1.15%时,可获得较高强度(抗拉强度419 MPa、屈服强度362 MPa)而又不损害其塑性(延伸率18.75%)。     

热处理对GWZ661变形镁合金组织与性能的影响

采用常规铸造和热形变相结合的工艺制备Mg-6Gd-6Y-1Zn四元镁合金,并对其显微组织和力学性能进行较系统的研究。结果表明:合金的铸态组织主要由α-Mg,Mg24(GdYZn)5和具有18R-LPSO结构的Mg12Y1Zn1相组成。合金热挤压过程中Mg12Y1Zn1相被拉长,呈长条状沿挤压方向排列,而14H-LPSO相则分布于Mg12Y1Zn1相之间。挤压态合金在高温固溶处理后,Mg12Y1Zn1相溶入基体,而基体中的14H-LPSO相增加。挤压态合金经固溶和时效(T6)处理后,显微组织中呈现18R-LPSO,14H-LPSO结构和β′沉淀颗粒共存。对挤压后的合金直接进行时效(T5)处理过程中也发生了β′沉淀,但14H-LPSO相体积分数没有T6态多。合金在T6态的性能最好,强度和塑性达到了良好的匹配。     

The microstructure and mechanical properties of as-cast Mg–4Y/Nd–2Zn alloys

Optical microscopy, scanning electron microscopy, X-ray diffraction and tensile testing were performed to investigate the microstructure and mechanical properties of as-cast Mg–4Y/Nd–2Zn alloys. The results show that the secondary dendritic arm spacing for the Mg–4Y–2Zn alloy is smaller than that for the Mg–4Nd–2Zn alloy, and that X-Mg₁₂YZn or W-Mg₃Zn₃Nd₂ form in Mg–4Y/Nd–2Zn alloys. The lamellar X phase distributes at the grain boundary, pointing into the grains, whereas the rod-like W phase preferentially segregates at the triangle junction of the grain boundary. The greater grain boundary strengthening effect and the smaller fragmentation effect of the brittle eutectic phases leads to the as-cast Mg–4Y–2Zn alloy having better comprehensive mechanical properties. The fracture mechanism for as-cast Mg–4Y/Nd–2Zn alloys is quasi-cleavage fracture.     

Effects of samarium content on microstructure and mechanical properties of Mg–0.5Zn–0.5Zr alloy

Effects of samarium (Sm) content (0, 2.0, 3.5, 5.0, 6.5 wt%) on microstructure and mechanical properties of Mg–0.5Zn–0.5 Zr alloy under as-cast and as-extruded states were thoroughly investigated. Results indicate that grains of the as-cast alloys are gradually refined as Sm content increases. The dominant intermetallic phase changes from Mg₃Sm to Mg₄₁Sm₅ till Sm content exceeds 5.0 wt%. The dynamically precipitated intermetallic phase during hot-extrusion in all Sm-containing alloys is Mg₃Sm. The intermetallic particles induced by Sm addition could act as heterogeneous nucleation sites for dynamic recrystallization during hot extrusion. They promoted dynamic recrystallization via the particle stimulated nucleation mechanism, and resulted in weakening the basal texture in the as-extruded alloys. Sm addition can significantly enhance the strength of the as-extruded Mg–0.5Zn–0.5 Zr alloy at room temperature, with the optimal dosage of 3.5 wt%. The optimal yield strength (YS) and ultimate tensile strength (UTS) are 368 MPa and 383 MPa, which were enhanced by approximately 23.1% and 20.8% compared with the Sm-free alloy, respectively. Based on microstructural analysis, the dominant strengthening mechanisms are revealed to be grain boundary strengthening and dispersion strengthening.     

Effect of Al on the microstructure and mechanical properties of Mg–6Zn–2Sn–0.5Mn alloy

The microstructure and mechanical properties of Mg–6Zn–2Sn–0.5Mn–xAl (x?=?0, 1, 2, 3) alloy are investigated. The addition of Al leads to the refinement of grain size and the formation of Al₆Mn, Mg₃₂(Al,Zn)₄₉ also forms when the amount of Al is higher than 2?wt-%. Because of the addition of Al, the precipitates in the alloy after ageing treatment are refined. The alloy containing 1?wt-% Al shows good mechanical properties in the as-cast state which is attributed to the refined grains and low volume fraction of large second phases, it also shows high strength after ageing treatment resulted mainly from the homogeneously distributed fine precipitates, the yield strength, ultimate tensile strength and elongation are 183, 310?MPa and 11%, respectively.     

Microstructure and mechanical properties of Mg–8Li–xAl–0.5Ca alloys

The effect of the Al content on the microstructure and mechanical behaviour of Mg–8Li–xAl–0.5Ca alloys is investigated. The experimental results show that an as-cast Mg–8Li–0.5Ca alloy is mainly composed of α-Mg, β-Li and granular Mg₂Ca phases. With the addition of Al, the amount of α-Mg phase first increases and then decreases. In addition, the intermetallic compounds also obviously change. The microstructure of the test alloys is refined due to dynamic recrystallisation that occurs during extrusion. The mechanical properties of extruded alloys are much more desirable than the properties of as-cast alloys. The as-extruded Mg–8Li–6Al–0.5Ca alloy exhibits good comprehensive mechanical properties with an ultimate tensile strength of 251.2?MPa, a yield strength of 220.6?MPa and an elongation of 23.5%.     

Microstructures and mechanical properties of Mg–Zn–Zr–Dy wrought magnesium alloys

Microstructures and phase compositions of as-cast and extruded ZK60–xDy (x?= 0–5) alloys were analysed by optical microscope, scanning electron microscope, X-ray diffraction and differential scanning calorimetry. Meanwhile, the tensile mechanical property was tested. With increasing Dy content, Mg–Zn–Dy new phase increases gradually, while MgZn₂ phase decreases gradually to disappear. As-cast microstructure is refined gradually; meanwhile extruded one is refined further with decreasing average grain size to 1 μm for ZK60–4·32Dy alloy. Second phase, tending to distribute along grain boundary by continuous network in as-cast state, breaks and distributes dispersedly in extrusion state. As-cast tensile mechanical property remains almost unchanged at ambient temperature; however, extruded ones are enhanced significantly at ambient and elevated temperatures, respectively. Tensile strength at 298 and 473 K increases gradually from 355 and 120 MPa for ZK60 alloy to 395 and 171 MPa for ZK60–4·32Dy alloy, respectively. Extruded tensile fractures exhibit a typical character of ductile fracture.     

Comparative studies on the microstructure evolution and fracture behavior between hot-rolled and as-cast Mg96ZnY3 alloys

Microstructure evolution and fracture mechanism of as-cast and hot-rolled Mg₉₆ZnY₃ alloys have been investigated in the present paper. Microstructure of the as-cast Mg₉₆ZnY₃ alloy consists of α-Mg dendrite and lamellar Mg₁₂YZn phase distributed mainly in interdendritic region. After a initial thickness reduction of ～ 62% through a series of rolling passes at 420 °C, the hot-rolled Mg₉₆ZnY₃ alloys were prepared by a final rolling reduction of 15% at 350 °C and 400 °C, respectively. The long period stacking order phase having a special orientation with α-Mg matrix in hot-rolled alloy was identified as 18R structure phase. Though highly dense dislocations were formed in the α-Mg matrix of the hot-rolled alloys, the parallel dislocations and sub-grain boundary were easily formed in the alloy during the recovery due to the relatively high working temperature of 400 °C. In the alloy rolled at 350 °C, the long period stacking order phase was traversed in the grain by the twins, which were induced by the relatively low working temperature. The morphology of dislocation and the influence of twin boundary may be the main reason for higher strength of the alloy rolled at 350 °C. While the tensile elongations for both as-cast and hot-rolled Mg₉₆ZnY₃ alloys are similar, their respective fracture mechanisms are different. The fracture along the phase interface of lamellar Mg₁₂YZn phase at grain boundary and cleavage fracture are considered as main fracture mechanisms for the as-cast alloy. The fracture caused by stress concentration at the phase interface between the matrix and Mg₁₂YZn phase in grain is the main fracture mechanism for the hot-rolled alloy.     

Thermal conductivity and mechanical properties of Sm-containing Mg-Zn-Zr alloys

This study investigated the effect of Sm additions on the microstructure, thermal conductivity, and mechanical properties of Mg-Zn-Zr alloy. The results indicate that the addition of Sm led to the formation of a rare-earth phase at the grain boundaries, and the grain size was significantly refined in the extruded state. The thermal conductivity of Mg alloy increased with the increase in Sm content because of the formation of a rare-earth phase that helps to dissolve the Zn atoms in the α-Mg matrix. Moreover, the as-extruded Mg alloy exhibited a higher thermal conductivity (up to124?W?(m?K)^?1) than its as-cast counterparts. The Sm-containing as-extruded Mg alloy showed excellent yield strength of up to 254?MPa, and also a good plastic deformation ability.     

热处理条件对锻造ZK60-Y镁合金力学性能的影响

研究了不同热处理条件下锻造ZK60-Y镁合金微观组织的变化对其力学性能的影响.结果表明,直接进行人工时效的合金具有优越的强度和塑性.XRD分析表明,析出相主要有Mg2Zn3、Mg24Y5、Zn2Zr3和w-Mg3Y2Zn3.Mg2Zn3和w-Mg3Y2Zn3等析出相的尺寸、数量及其在基体中的分布状态对合金的力学性能影响很大.锻造态下大块破碎呈带状分布的Mg3Y2Zn3相及T4和T6态下粗化呈片层状的Mg2Zn3相是合金力学性能降低的主要原因.细小呈带状分布的Mg3Y2Zn3相和细层片状分布的Mg2Zn3相及其在此状态下细小的晶粒使T5态合金具有优越的抗拉强度和塑性.     

Effects of Ca on microstructure, mechanical and corrosion properties and biocompatibility of Mg–Zn–Ca alloys

Zn and Ca were selected as alloying elements to develop an Mg–Zn–Ca alloy system for biomedical application due to their good biocompatibility. The effects of Ca on the microstructure, mechanical and corrosion properties as well as the biocompatibility of the as-cast Mg–Zn–Ca alloys were studied. Results indicate that the microstructure of Mg–Zn–Ca alloys typically consists of primary α-Mg matrix and Ca₂Mg₆Zn₃/Mg₂Ca intermetallic phase mainly distributed along grain boundary. The yield strength of Mg–Zn–Ca alloy increased slightly with the increase of Ca content, whilst its tensile strength increased at first and then decreased. Corrosion tests in the simulated body fluid revealed that the addition of Ca is detrimental to corrosion resistance due to the micro-galvanic corrosion acceleration. In vitro hemolysis and cytotoxicity assessment disclose that Mg–5Zn–1.0Ca alloy has suitable biocompatibility.     

Microstructure,mechanical and corrosion properties and biocompatibility of Mg–Zn–Mn alloys for biomedical application

Mn and Zn were selected to develop a Mg–Zn–Mn magnesium alloy for biomedical application due to the good biocompatibility of Zn and Mn elements. Microstructure, mechanical properties, corrosion properties and biocompatibility of the Mg–Zn–Mn alloys have been investigated by use of optical microscope, scanning electron microscope, tensile testing, and blood hemolysis and cell toxicity. Microstructure observation has shown that the addition of Zn and the extrusion significantly refined the grain size of both the as-cast and the extruded magnesium alloys, which mainly contributes to the high tensile strength and good elongation. Polarization test has shown Zn could accelerate the formation of a passivation film, which provides good protection to the magnesium alloy against simulate body fluid. Cell culture and hemolysis tests have shown that the magnesium alloy did not have cell toxicity, showing good cytocompatibility, but the alloy caused hemolysis to blood system. It was suggested that surface modification have to be adopted to improve the blood compatibility of the magnesium alloy for the application in blood environment.