微量镱和过渡元素对Al-Zn-Mg-Cu超强合金晶界特征和性能的影响

通过电子背散射衍射实验对复合添加稀土元素Yb和过渡族元素Zr或Cr的Al-Zn-Mg-Cu超高强合金的晶粒尺寸、晶界类型、晶界特性进行研究,分析了微合金化后的晶界特性对合金力学性能和局部腐蚀(晶间腐蚀和剥落腐蚀)的影响。结果表明:与复合添加Yb和Cr相比,复合添加Yb和Zr的Al-Zn-Mg-Cu合金具有最佳的再结晶抑制效果;高温固溶-时效处理后,合金晶粒尺寸由40μm显著细化到2.3μm,再结晶程度从98%下降到3%,Σ27晶界所占比例大幅提高,小角度晶界所占比例由8%提高到51%;亚晶界上的析出相与晶内的析出相近似,合金的力学性能和耐腐蚀性能显著提高,使得合金拉伸断裂时,沿晶断裂分数大幅降低,合金的力学性能和耐腐蚀性能显著提高。     

微量Cr和Nb对Al-Zn-Mg-Cu-Zr合金力学性能和应力腐蚀性能的影响

通过金相显微分析、硬度、强度和应力腐蚀性能的测试,研究添加微量Cr和Nb对Al-Zn-Mg-Cu-Zr合金力学性能、再结晶与应力腐蚀行为的影响。结果表明,在Al-Zn-Mg-Cu-Zr合金中添加微量Cr和Nb能提高合金的抑制再结晶能力,并显著提高合金的抗应力腐蚀性能,使合金在保持高的强度和塑性的同时,应力腐蚀临界应力强度因子KISCC由9．8MPa·m^1/2提高N15．2MPa·m^1/2。     

微量Zr、Er对Al-Zn-Mg合金组织与性能的影响

采用硬度、拉伸性能、电阻率和抗应力腐蚀性能测试及金相组织观察等方法,研究了微量Zr、Er对Al-4.4Zn-2.4Mg(质量分数,下同)合金组织与性能的影响.结果表明,单独添加Zr的细晶作用优于单独添加Er以及Er、Zr复合添加,Er、Zr复合添加能显著抑制合金的再结晶行为,Er、Zr复合添加后合金的力学性能和单独添加微量Zr的基本相当,但Er、Zr复合添加后合金抗应力腐蚀性能优于单独添加微量Er、Zr,Er、Zr复合添加的Al-Zn-Mg合金综合性能最好.Er、Zr复合添加提高应力腐蚀抗力是通过抑制再结晶获得纤维组织间接实现的.     

Er、Zr微合金化对Al-Zn-Mg合金组织及性能的影响

研究了Er、Zr元素的添加对Al-Zn-Mg合金的微观组织、力学性能和腐蚀性能的影响。结果表明,Er、Zr元素的复合添加可以使合金的硬度、强度以及抗腐蚀性能有明显提高。Er、Zr元素的添加形成了弥散分布的纳米级Al₃(Er, Zr)析出相,阻碍位错运动和晶界迁移,使合金的强度得到明显提高。另外,Er元素的添加使合金的晶粒细化,既提高了强度也保证了一定的伸长率,还使合金具有良好的抗剥落腐蚀性能。     

微量Zr和Si对体育器材用Al-Zn-Mg合金组织和耐蚀性的影响

采用光学显微镜(OM)、透射电镜(TEM)、电化学试验、拉伸试验、双悬臂梁(DCB)试验等方法，研究了Zr、Si含量对体育器材用Al-Zn-Mg合金组织、拉伸性能和在3.5%NaCl溶液中耐蚀性的影响。结果表明：添加微量Zr、Si对合金组织和性能均产生明显影响，复合添加Zr、Si比单独添加Zr效果更好；在合金中添加0.15%Zr后，合金晶粒尺寸明显减小，但部分再结晶晶粒长大；在合金中复合添加0.15%Zr和0.08%Si后，合金晶粒尺寸进一步减小，且晶粒尺寸大小均一，呈等轴晶状；与未添加Zr、Si的合金相比，复合添加0.15%Zr和0.08%Si的合金的平均晶粒尺寸由177.8μm降低到6.8μm,抗拉强度和屈服强度由283.6 MPa和249.2 MPa提升至368.1 MPa和319.2 MPa,应力强度因子K_ISCC由3.2提升至10.9,合金的抗电化学腐蚀性能显著提高。     

复合添加Cr、Mn、Zr对Al-Zn-Mg合金组织和性能的影响

通过光学显微镜、扫描电镜、透射电镜观察以及拉伸试验等手段,研究Cr、Mn、Zr微合金元素对Al-Zn-Mg合金组织和性能的影响。结果表明:复合添加Zr、Mn、Cr在基体上析出大量不规则的、直径为10~20 nm与基体共格的(Al,Cr)₃Zr粒子。(Al,Cr)₃Zr粒子弥散相能强烈钉扎位错、阻碍位错和亚晶界迁移,显著抑制再结晶和晶粒长大。复合添加Zr、Mn、Cr的Al-Zn-Mg合金的抗拉强度和规定塑性延伸强度分别提高34 MPa、19 MPa,具有较好的加工性能和力学性能。     

Zr、Sc对Al-Cu-Mg-Ag-Ti合金耐蚀性能的影响

通过晶间腐蚀、慢拉伸试验和电化学测试,研究了Zr、Sc对Al-Cu-Mg-Ag-Ti多元合金耐蚀性能的影响。结果表明,添加Zr能够提高合金的耐蚀性,含Zr合金的应力腐蚀敏感因子(I_(scc))都小于不含Zr的,但Zr、Sc复合添加并没有进一步提高合金的耐蚀性。Zr能够抑制合金的再结晶,使无沉淀析出带变窄,大大提高了合金的耐蚀性能。Zr含量为0.19%时合金的综合性能最佳,晶间腐蚀深度最浅,I_(scc)最小,抗拉强度最高,其屈服强度和抗拉强度分别为466 MPa和518 MPa。     

高温预析出对7A52合金应力腐蚀性能的影响

通过对7A52合金时效状态的强度、硬度、电阻率和应力腐蚀性能的测试,对比分析了高温预析出对7A52合金T4和T61时效状态应力腐蚀和强度性能的影响.结果表明:高温预析出可以提高7A52-T4和7A52-T61合金的抗应力腐蚀性能,同时其强度和延伸率有所增加;高温预析出处理的7A52-T61合金拉伸强度达500MPa,延伸率13.0%,KISCC达到10.2 MPa·m1/2.     

Cr、Yb合金化对Al-Zn-Mg-Cu-Zr合金组织和断裂特征的影响

研究复合添加微量Cr、Yb、Zr对Al-Zn-Mg-Cu合金的显微组织和断裂特征的影响,分析其对合金韧化的作用机制.结果表明:在Al-Zn-Mg-Cu合金中复合添加Cr、Yb、Zr形成了含Cr、Yb、Zr的球形弥散相,这些均匀分布于基体上的弥散相能强烈钉扎位错和亚晶界,使基体保持形变回复组织,保持小角度晶界,抑制基体再结晶;T6态断裂机制主要为韧窝型穿晶断裂,与仅添加Zr相比,沿晶断裂抗力显著提高;晶界的无沉淀区(PFZs)较宽,且析出相在晶界呈明显不连续分布.     

低合金高强度抗应力腐蚀开裂海洋软管用钢的开发

通过合金成分设计,轧制、热处理工艺的探索,开发了低合金高强度海洋软管用钢,其屈服强度大于600 MPa且满足抗氢脆、抗氢致开裂、抗应力腐蚀开裂性能,并通过全浸腐蚀实验对该钢的海水腐蚀行为进行了研究。结果表明,采用低C、低Mn并复合添加耐蚀元素Cr、Mo和采用合理的热轧、冷轧、调质处理工艺,可获得满足抗应力腐蚀开裂性能的600 MPa级高强钢。耐蚀元素的添加使实验钢具有良好的耐海水腐蚀能力,腐蚀稳定状态下的平均年腐蚀速率为0.11 mm/a。     

Sc、Zr对Al-Zn-Mg-Cu合金组织与性能的影响

制备了成分Al-5．8Zn-2．5Mg-1．6Cu-0．2Cr和Al-5．8Zn．2．5Mg-1．6Cu-0．2Cr-0．23Sc-0．12Zr的两种合金。通过金相显微镜及电镜观察、力学性能及腐蚀性能测试，分析了两种合金不同处理状态的显微组织及其不同状态下的力学性能和腐蚀性能。结果表明，添加Sc、Zr能显著细化合金的铸态组织，对合金的力学性能及腐蚀性能也起到极大的提高作用。添加Sc、Zr的2#合金与1#合金相比较，经T6处理后，前者的抗拉强度提高110N／mm^2，屈服强度提高91N／mm^2，伸长率也略有提高。     

Effect of minor Sc and Zr addition on microstructures and mechanical properties of Al-Zn-Mg-Cu alloys

Three kinds of Al-Zn-Mg-Cu based alloys with 0.22%, 0.36%（Sc＋Zr） （mass fraction, %）, and without Sc, Zr addition were prepared by ingot metallurgy. By using optical microscopy, transmission electronic microscopy and scanning electron microscopy, the effects of microalloying elements of Sc, Zr on the microstructure of super-high-strength Al-Zn-Mg-Cu alloys related to mechanical properties were investigated. The tensile properties and microstructures of the studied alloys under different heat treatment conditions were studied. The addition of minor Sc, Zr results in the formation of Ala（Sc,Zr） particles. These particles are highly effective in refining the microstructures, retarding recrystallization, pinning dislocations and subboundaries. The strength of Al-Zn-Mg-Cu alloys was greatly improved by simultaneously adding minor Sc, Zr, meanwhile the ductility of the studied alloys remains at a higher level. The 0.36%（Sc＋Zr） alloys gain the optimal properties after 465 ℃/h solution and 120 ℃/24 h aging. The increment of strength is mainly due to strengthening of fine grain and substructure and precipitation ofAl3（Sc, Zr） particles.     

Identification and analysis of intermetallic phases in overaged Zr-containing and Cr-containing Al-Zn-Mg-Cu alloys

This paper investigates the effect of alloying elements on the characteristics of intermetallic phases in Zr-containing and Cr-containing 7xxx Al-Zn-Mg-Cu alloys at overaged conditions. Four Al-Zn-Mg-Cu alloy plates with different alloying element contents were studied by optical microscopy based image analysis, differential scanning calorimetry, scanning electron microscopy combined with energy disperse X-ray spectroscopy and transmission electron microscopy. The grain structures, recrystallisation, intermetallic phases and precipitates in the selected alloys have been analyzed and the presence of coarse intermetallic phases has been interpreted using established phase diagrams. The different effects of Zr or Cr addition to the alloys have been compared. The experimental results showed that the recrystallised area fraction of Zr-containing alloys is less than that of Cr-containing alloys, being attributable to Zr reducing recrystallisation more effectively than Cr. The detected particles are mainly S phase, Al₇Cu₂Fe, as well as dispersoids of Al₃Zr for Zr-containing alloys and Cr-rich E phase for Cr-containing alloys. These coarse particles, especially the S phase which cannot be dissolved during solution treatment, are detrimental to the fracture toughness of the alloys.     

Effect of Solution Treatment on Microstructure and Corrosion Properties of Mg–4Gd–1Y–1Zn–0.5Ca–1Zr Alloy

The as-cast multi-element Mg–4Gd–1Y–1Zn–0.5Ca–1Zr alloy with low rare earth additions was prepared, and the solution treatment was applied at different temperatures. The microstructural evolution of the alloy was characterized by optical microscopy and scanning electron microscopy, and corrosion properties of the alloy in 3.5% NaCl solution were evaluated by immersion and electrochemical tests. The results indicate that the as-cast alloy is composed of the a-Mg matrix,lamellar long-period stacking-ordered(LPSO) structure and eutectic phase. The LPSO structure exists with more volume fraction in the alloy solution-treated at 440 °C, but disappears with the increase in the solution temperature. For all the solution-treated alloys, the precipitated phases are detected. The corrosion rates of the alloys decrease first and then increase slightly with the increase in the solution temperature, and the corrosion resistance of the solution-treated alloys is more than four times as good as that of the as-cast alloy. In addition, the alloy solution-treated at 480 °C for 6 h shows the best corrosion property.     

Yb微合金化对Al-Zn-Mg-Cu-Zr合金再结晶行为和性能的影响

采用铸锭冶金法制备了含Yb的Al-Zn-Mg-Cu-Zr合金.通过对硬度、电阻率、强度、应力腐蚀性能的测试和用金相显微镜和透射电镜的观察,分析了Yb微合金化对Al-Zn-Mg-Cu-Zr合金再结晶行为和性能的影响.结果表明,在Al-Zn-Mg-Cu-Zr合金中添加微量Yb能形成含Yb的细小弥散相,因此提高T6态合金的再结晶温度,显著提高合金的应力腐蚀抗力和断裂韧性,并略微提高合金的强度和塑性.这些均匀分布于基体上的弥散相能强烈钉扎位错和亚晶界,抑制了再结晶形核,显著抑制了基体再结晶,保持形变回复组织.     

Effect of Mg Additions and Thermal Treatment on Corrosion Properties of Al–Li–Cu-Base Alloys

An investigation on the corrosion and electrochemical behavior of experimental and industrial semifinished items of Al–Li–Cu–base alloys offers possibilities of increasing the corrosion resistance of aluminum–lithium alloys by alloying and an nontraditional thermal treatment. Magnesium added in a concentration of no more than 0.4% leads to a improvement of the corrosion and mechanical characteristics of the alloy, whereas increasing its concentration up to 1.0% deteriorates all the corrosion characteristics. An investigation of the effect of the cathodic additions of Zr, Mn, and Mn + Cr shows that the corrosion properties are nonchanged by substitution of Mn or Mn + Cr for Zr. The resistance to general corrosion, exfoliation corrosion, and corrosion cracking is enhanced by a nontraditional artificial aging.     

微量Cr、Mn、Zr、Ti、B元素对铸态AlZnMgCu合金的晶粒细化效果的影响

采用光学显微镜、扫描电镜和能谱分析仪考察了Cr、Mn、Zr、Ti、B的联合加入对AlZnMgCu合金的晶粒细化效果。结果发现在铸态合金中同时加入Cr-Mn-Ti-B时晶粒尺寸由256 μm 降为102 μm。而当联合加入Ti-Zr-B后能产生更加强的细化效果,晶粒平均尺寸降为55 μm。这是因为Cr、Mn原子簇团有利于促进Al3Ti形核并成为其结晶基底。当联合加入Cr、Mn、Zr、Ti、B时则可产生更加明显的晶粒细化效果,平均晶粒尺寸变为22 μm。这是因为富Cr、Mn原子簇团在成为Al3Ti结晶核心后,部分Zr原子置换了其中的Ti原子形成了新的Al3(Tix, Zr1-x)结晶核心。而过渡族金属Cr、Mn还能降低液体金属和Al3Ti和Al3(Tix, Zr1-x)的表面张力,抑制结晶核心的长大。     

Effect of Yb additions on microstructures and properties of 7A60 aluminum alloy

Al-Zn-Mg-Cu-Zr alloys containing Yb were prepared by cast metallurgy. Effect of 0.30% Yb additions on the microstructure and properties of 7A60 aluminum alloys with T6 and T77 aging treatments was investigated by TEM, optical microscopy, hardness and electric conductivity measurement, tensile test and stress corrosion cracking test. The results show that the Yb additions to high strength Al-Zn-Mg-Cu-Zr aluminum alloys can produce fine coherent dispersoids. Those dispersoids can strongly pin dislocation and subgrain boundaries, which can significantly retard the recrystallization by inhibiting the nucleation of recrystallization and the growth of subgrains and keeping low-angle subgrain boundaries. Yb additions can obviously enhance the resistance to stress corrosion cracking and the fracture toughness property, and mildly increase the strength and ductility with T6 and T77 treatments.     

Ni- and Cu-free Ti-based metallic glasses with potential biomedical application

In the present work Ti–Fe–Si and Ti–Fe–Si–X (X = Zr, Pd, Ge) glassy alloys are discussed as potential biomedical materials. Depending on composition and experimental conditions these alloys possess glassy, quasicrystalline or crystalline structure. The glassy state and crystallization behavior of the melt spun ribbons were studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and the Hank's solution was used as simulated body fluid for corrosion tests. Ternary Ti–Fe–Si alloys near the Ti₆₅Fe₃₀Si₅ eutectic point were prone to form quasicrystals if the cooling rate was not high enough to retain amorphous structure. The compositions on the steeper side of the eutectic point could be vitrified. The results indicate that small additions of Zr can have a positive effect on glass formation, while additions of Ge, Pd may have a detrimental effect by promoting crystallization. Ti–Fe–Si and Ti–Fe–Si–Zr alloys exhibited high corrosion properties, superior to that of pure Ti and most of Ti-based glassy alloys reported in the literature. Being free of Ni and Cu this group of alloys may be considered for possible biomedical application.