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。     

Y对ZK60镁合金组织与性能的影响研究

以ZK60为母合金,通过添加不同量的稀土元素Y,制备了2种Mg-Zn-Y-Zr合金.用扫描电镜和X射线衍射对合金铸态组织进行观测和分析发现,在ZK60合金中添加质量分数为1.04%的Y后,组织中析出I相(Mg3Zn6Y).当Y的加入量增至2.10%,合金组织中主要析出W相(Mg3Zn3Y2)伴有微量的I相.I相和W相呈层片状分布在晶界处,有少量呈棒状,分布在晶内.这些细小、弥散分布的第二相对合金产生显著的强化作用,改善了合金的热加工性能,使得ZK60合金易热裂的缺点得到明显改善,在340～380℃温度范围内挤压没有发生热裂.实验表明,添加Y的挤压棒材的拉伸强度有较大幅度提高,延伸率略有增加.     

Mg-11Y-5Gd-2Zn-0.5Zr(wt.%)合金的显微组织和力学性能

采用光学显微镜(OM)、带能谱分析(EDAX)的扫描电子显微镜(SEM)、X射线衍射仪(XRD)等方法对Mg-11Y-5Gd-2Zn-0.5Zr(WGZ115)合金的原始铸态(F态)、固溶处理态(T4态)和峰值时效态(T6态)的组织结构进行了分析。研究表明:F态WGZ115合金主要由基体(-αMg)、晶间共晶相(Mg24(YGdZn)5)和长周期结构相(Mg12Y1Zn1)组成。T4态WGZ115合金主要由基体相(-αMg)、长周期结构相(Mg12Y1Zn1)和少量分布于晶界附近的方块相(Mg-Y-Gd方块相)组成。T6态WGZ115合金的形貌与T4态相似,圆形的富Zr相始终存在于三种状态的合金中。通过不同温度下的拉伸实验发现T4态WGZ115合金的抗拉强度和塑性好于F态合金。而T6态合金的力学性能最好,在200℃时抗拉强度达到最大值341.1MPa。     

合金元素对A7N01S-T5铝合金力学性能和断裂韧性的影响

测试4种A7N01S-T5铝合金的力学性能和断裂韧性,研究了不同合金元素的影响。结果表明:影响A7N01S-T5铝合金性能的3类合金元素适宜的成分配比为Zn(4.34)、Mg(1.43),Mn(0.27)、Cr(0.13),Zr(0.12)、Ti(0.066)。在此条件下,合金的抗拉强度、屈服强度、伸长率、冲击功和断裂韧度分别为415 MPa,378 MPa,13.49%,12.3J和28.950 k J·m-2。极差分析表明,Zn、Mg含量是合金强度与塑性共同的主要影响因素。因此,为了制备出综合性能优异的合金,需选取适当的Zn、Mg含量。对于成分配比适宜的合金,其晶内析出相η′(Mg Zn2)呈细小弥散状分布,而晶界析出相η(Mg Zn2)粗大,呈断续状分布。     

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。     

Mg-5Yb-0.5Zr变形镁合金的显微组织与力学性能

本文利用熔剂保护法制备了Mg-5Yb-0.5Zr合金,并进行了热挤压和热处理,对合金在各种加工状态下的相结构、显微组织和力学性能进行了试验和测试.结果表明,合金由α-Mg和Mg2Yb相组成,铸态组织中的Mg2Yb相聚集在晶界,并在热挤压过程中被破碎起到限制再结晶和弥散强化的作用;合金经热处理后有一定的时效强化效应,析出相为共轭生长的短棒状Mg2Yb颗粒.合金在挤压态的强度最高,T5态热处理可得到良好的综合力学性能.     

稀土Y对Mg-6Zn-1Mn合金显微组织和力学性能的影响

利用光学显微镜、X射线衍射仪、扫描电子显微镜、万能力学试验机等手段,系统研究了不同含量Y(1%~6%(质量分数))对Mg-6Zn-1Mn合金显微组织和力学性能的影响。结果表明,随着Y的不断增加,Mg-6Zn-1Mn系铸态合金主要物相演变规律为α-Mg+Mg7Zn3→α-Mg+I→α-Mg+W→α-Mg+X,这主要归因于不同的Zn/Y原子比。研究发现,当Y含量低于2%时,挤压可使晶界和晶粒内部析出细小弥散的第二相,同时提高了合金强度和室温延展性。而随着Y的进一步增加,第二相颗粒变大,且主要存在于晶界,热挤压过程中晶粒不易被挤碎,弱化了析出相与基体的界面能,最终使得挤压态合金综合力学性能降低。     

Si对AM30变形镁合金组织和力学性能的影响

为了提高Mg-3Al-0.4Mn合金的常温力学性能,研究了铸态和挤压态下Si含量对AM30合金的组织和力学性能的影响.结果表明,增加Si的添加量会生成粗大的汉字状的Mg2Si相,不利于提高合金的力学性能;但经过挤压后,呈汉字状Mg2Si相破碎,变成颗粒细小的Mg2Si相,晶粒细化,有利于提高合金的性能.     

Sm对Mg-l0Y合金组织的细化作用

Mg24Y5相的细化是进一步提高Mg-l0Y合金力学性能的关键.研究了稀土元素sm对Mg-l0Y合金中的Mg24Y5相及其基体组织的细化作用,结果表明:sm的加人,改善了Mg24Y5相的形貌,促进了细小弥散分布的Mg24Y5颗粒相的形成;同时,Sm的加人,通过固溶作用,进一步细化了基体组织;显微组织的改善导致了合金高温...     

高强高韧Mg-8.5Gd-2.0Y-1.0Ag-0.4Zr合金的组织与性能

研究了高强高韧Mg-8.5Gd-2.0Y-1.0Ag-0.4Zr(wt.%)合金的显微组织和力学性能。结果表明,该合金铸态组织细小,主要由α-Mg固溶体、晶界析出相Mg5(GdY)以及分布在晶粒内部的Zr核组成;T4态时晶界析出相基本完全消失,但出现了一些方块相γ;合金具有明显的时效硬化效果,且随着时效温度的提高,合金的峰值时效硬度下降,峰值时间相应缩短。经200℃峰值时效处理后表现出极为优异的室温力学性能,抗拉强度(UTS)和延伸率分别达到396MPa和9.1%,显著的时效强化是该合金具有优异力学性能的主要原因。如此优异的强度和塑性在常规铸造镁合金中是极为罕见的,对于推广镁合金的应用具有重要意义。     

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.     

Quasicrystal-reinforced Mg alloys

The formation of the icosahedral phase (I-phase) as a secondary solidification phase in Mg–Zn–Y and Mg–Zn–Al base systems provides useful advantages in designing high performance wrought magnesium alloys. The strengthening in two-phase composites (I-phase + α-Mg) can be explained by dispersion hardening due to the presence of I-phase particles and by the strong bonding property at the I-phase/matrix interface. The presence of an additional secondary solidification phase can further enhance formability and mechanical properties. In Mg–Zn–Y alloys, the co-presence of I and Ca₂Mg₆Zn₃ phases by addition of Ca can significantly enhance formability, while in Mg–Zn–Al alloys, the co-presence of the I-phase and Mg₂Sn phase leads to the enhancement of mechanical properties. Dynamic and static recrystallization are significantly accelerated by addition of Ca in Mg–Zn–Y alloy, resulting in much smaller grain size and more random texture. The high strength of Mg–Zn–Al–Sn alloys is attributed to the presence of finely distributed Mg₂Sn and I-phase particles embedded in the α-Mg matrix.     

不同应变率下MgAlZnY合金的拉伸性能与断口研究

利用材料试验机开展了室温拉伸实验,在0.001,0.1,0.6s-1不同应变率下,研究了Mg3Al1Zn2Y,Mg3Al2Zn2Y与Mg3Al6Zn2Y合金流动应力的应变率敏感性,其大小为Mg3Al2Zn2YMg3Al1Zn2YMg3Al6Zn2Y。基于分形理论和计算机图像处理技术,结合扫描电镜分析,研究了合金断裂特征,结果表明:合金在不同应变率拉伸下的断口分形行为显著,分形维数可将断口的韧脆性与形貌特征联系起来,分形维数越大,合金塑性相对越好,合金越倾向于延性断裂,断口形貌也越复杂;三种合金断裂特性的应变率敏感性大小为Mg3Al2Zn2YMg3Al6Zn2YMg3Al1Zn2Y,且表现出正负不同的应变率效应。     

Zn添加对挤压态Mg-Al-Ca-Mn合金微观组织和力学性能的影响

目的 研究不同含量Zn元素对镁合金塑性、强度的改良效果.方法 以Mg-Al-Ca-Mn合金为基础,采用热挤压成形加工方法,分析不同Zn含量对其显微组织和力学性能的影响.结果 Zn元素可以改变挤压态镁合金的显微组织,对其主合金相影响不大,但可以改变衍射峰强度.Zn元素可以提高挤压态镁合金的屈服强度和伸长率,提高镁合金韧性...     

合金成分对Mg-Zn-Y合金准晶形貌和体积分数的影响

利用铁模铸造法制备Zn/Y=6:1(原子比)的Mg-Zn-Y合金,通过XRD,SEM,EDS,TEM和DSC等研究合金成分对Mg-Zn-Y合金相组成、Mg_3Zn_6Y准晶相(准晶Ⅰ相)形貌和体积分数的影响。结果表明:Mg-Zn-Y合金的相组成、准晶Ⅰ相形貌、体积分数及其生成反应与合金成分密切相关。随着合金中Zn和Y元素含量的减少,准晶Ⅰ相的形成反应由单一的包晶反应到包-共晶反应再到完全共晶反应。当合金中Y含量≥7%(原子分数,下同)时,合金由(Mg, Zn)_5Y、准晶Ⅰ相、Mg_2Zn_3和Mg_7Zn_3相组成,且以叠层状形式分布在合金组织中。合金在凝固过程中通过包晶反应形成多边形块状准晶Ⅰ相;当Y含量<7%时,合金中除(Mg, Zn)_5Y、准晶Ⅰ相和Mg_7Zn_3相外,还析出了Mg相。当合金中Y含量在5%～7%时,准晶Ⅰ相通过包晶和共晶反应生成,以共晶反应为主。当Y含量≤4%时,准晶Ⅰ相完全通过共晶反应形成(Mg+I-phase)层片状共晶组织。所研究的合金中均生成了体积分数大于27%的准晶Ⅰ相,Mg₃₀Zn₆₀Y₁₀合金中准晶Ⅰ相的体积分数最高,约为77%。     

Zn对铸态Mg-Y-Nd-Zr合金组织和力学性能的影响

采用光学显微镜(OM)、扫描电子显微镜(SEM)、X射线衍射分析及力学性能测试等研究Zn元素对Mg-Y-Nd-Zr铸态合金显微组织及力学性能的影响。结果表明:随着Zn含量的增加,Mg-Y-Nd-Zr-xZn(x=0.0%,0.5%,1.0%,1.5%,质量分数)合金的晶粒逐渐细化,平均晶粒尺寸由(57±0.8)μm细化至(30±0.3)μm,晶界处共晶相的体积分数也逐渐增加。Mg-Y-Nd-Zr铸态合金中主要存在Mg12Nd相和Mg24Y5相,加入0.5%Zn后,合金中出现Mg12YZn相。随Zn含量的增加,Mg12YZn相的体积分数不断增大,合金的力学性能逐渐提高。当Zn含量为1.0%时,合金具有最优的力学性能,其抗拉强度、屈服强度和伸长率分别为(208±5.9),(159±3.9)MPa和(7.5±0.2)%,较未加Zn的合金分别提高了18,42MPa和1.2%。     

Effect of microstructure and texture on the mechanical properties of the as-extruded Mg–Zn–Y–Zr alloys

This work mainly studied the influence of the microstructure and crystallographic texture on the mechanical properties of the as-extruded Mg–Zn–Y–Zr alloys with different Y contents. The samples were machined from thick plates obtained by extrusion and the tensile tests were performed parallel to extrusion and transverse directions, respectively. Microstructure observation firmly indicated that the grain-refining effect of icosahedral quasicrystal phase (I-phase) was superior to that of the cubic W-phase. In addition, the tensile results indicated that I-phase could effectively improve the strength (yield strength and ultimate tensile strength) of alloys. However, strengthening effect of W-phase was lower. With the quantity of W-phase increasing, the strength of alloys was degraded. It also showed that the alloys were mechanically anisotropic, i.e. the longitudinal strength was higher than that of the transverse direction. However, the ductility of the transverse direction was superior. With the increase of Mg–Zn–Y phases, the anisotropy of the ultimate tensile strength (UTS) between the longitudinal and transverse directions increased remarkably. SEM fracture observations showed that the fractures of the TD samples were characterized by the typical “woody fracture”, with a large amount of cracked Mg–Zn–Y particles (I-phase and W-phase) distributed at the bottom of dimples. With Y content increasing, the average spacing of the zonal distributed Mg–Zn–Y particles on the fracture surface became narrow, which influenced the transverse mechanical properties greatly.     

Al-Zn-Mg-Cu系超高强度铝合金的研究进展

Al-Zn-Mg-Cu系超高强度铝合金具有低密度、高比强度、高韧性和良好的抗腐蚀性能的特点,广泛应用于航空航天、交通运输和兵器领域。本文主要介绍近年来国内外Al-Zn-Mg-Cu系超高强度铝合金的最新研究进展。超高强度铝合金基体上分布着纳米级的晶内时效析出相、亚微米级的高温析出相、微米级的结晶析出相和晶界析出相,这些相的形态、数量、尺寸和分布对合金的综合力学性能和抗腐蚀性能有直接的影响;主元素成分含量对超高强度铝合金综合力学性能有影响,合金的综合力学性能随Zn/Mg和Cu/Mg比值的变化而变化;微量元素能够提高超高强度铝合金的综合力学性能。微量元素对铝合金的影响主要体现在提高沉淀相的过饱和度,改变沉淀析出过程,促进或抑制沉淀相的析出和促进新相的沉淀析出。新制备技术能够显著细化晶粒、抑制偏析、析出相均匀分布和提高各种元素的过饱和度,从而改善超高强度铝合金的综合力学性能。强化固溶处理能够提高时效析出程度,从而提高铝合金的力学性能。三级时效处理后的超高强度铝合金具有峰值时效T6态的强度和优异的抗腐蚀性能。     

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.     

Mechanical and bio-corrosion properties of quaternary Mg–Ca–Mn–Zn alloys compared with binary Mg–Ca alloys

Binary Mg–xCa alloys and the quaternary Mg–Ca–Mn–xZn were studied to investigate their bio-corrosion and mechanical properties. The surface morphology of specimens was characterized by X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results of mechanical properties show that the yield strength (YS), ultimate tensile strength (UTS) and elongation of quaternary alloy increased significantly with the addition of zinc (Zn) up to 4 wt.%. However, further addition of Zn content beyond 4 wt.% did not improve yield strength and ultimate tensile strength. In contrast, increasing calcium (Ca) content has a deleterious effect on binary Mg–Ca alloys. Compression tests of the magnesium (Mg) alloys revealed that the compression strength of quaternary alloy was higher than that of binary alloy. However, binary Mg–Ca alloy showed higher reduction in compression strength after immersion in simulated body fluid. The bio-corrosion behaviour of the binary and quaternary Mg alloys were investigated using immersion tests and electrochemical tests. Electrochemical tests shows that the corrosion potential (E_corr) of binary Mg–2Ca significantly shifted toward nobeler direction from −1996.8 to −1616.6 mV_SCE with the addition of 0.5 wt.% manganese (Mn) and 2 wt.% Zn content. However, further addition of Zn to 7 wt.% into quaternary alloy has the reverse effect. Immersion tests show that the quaternary alloy accompanied by two secondary phases presented higher corrosion resistance compared to binary alloys with single secondary phase. The degradation behaviour demonstrates that Mg–2Ca–0.5Mn–2Zn alloy had the lowest degradation rate among quaternary alloys. In contrast, the binary Mg–2Ca alloy demonstrated higher corrosion rates, with Mg–4Ca alloy having the highest rating. Our analysis showed the Mg–2Ca–0.5Mn–2Zn alloy with suitable mechanical properties and excellent corrosion resistance can be used as biodegradable implants.