微量钪对Al-15Ag合金时效特性与微观组织的影响

通过时效硬化曲线测量及时效组织分析,研究了微量钪对Al-15Ag合金时效行为和显微组织的影响。在Al-15Ag合金中添加0．2％Sc(质量分数,下同),可以增强合金在190℃和350℃时效的时效硬化效果,延长峰时效的到达时间。微量钪的添加促使合金中y’相细小密集地析出,同时钪的存在减少了y’相宽面上的位错台阶数。含钪Al-15Ag合金中y’相长大过程比较缓慢的微观机理是微量钪的添加影响了合金中y’相宽面上的台阶分布。     

含钪Al-Cu-Li合金的形变时效研究

通过显微组织观察和室温拉伸试验，研究了形变时效对含钪Al-Cu-Li合金组织和拉伸性能的影响。结果表明，时效前的预变形能促进T1(Al2CuLi)相弥散细小的析出，显著提高合金的强度，使时效峰值提前。合金的强度随预变形量的增大而升高，但预变形量过大，不利于T1相的析出形态和分布，影响合金的性能。在本试验条件下，该合金的最佳预变形量为3．5％。     

微量钪对Al-2．5Cu-1．5Mg合金时效特性与微观组织的影响

研究了微量钪对Al-2．5Cu-1．5Mg合金微观组织与时效特性的影响。结果表明,微量钪的添加增强了Al-2．5Cu-1．5Mg合金的时效硬化效果,但并未改变该合金时效硬化的总体规律。透射电镜分析发现GPB在合金时效硬化第二阶段初期才开始析出,并且是该合金第二阶段硬化的主要原因,微量钪的添加促进了Al-2．5Cu-1．5Mg合金中GPB的弥散细小析出。     

外加应力对Al-Cu-Mg-Ag合金时效析出行为的影响

采用维氏硬度、光学显微镜、双臂电桥电阻及透射电子显微镜等手段,研究普通时效与应力时效时,外加应力对Al-Cu-Mg-Ag合金时效析出行为的影响。结果表明:外加应力会降低Al-Cu-Mg-Ag合金的时效硬化速率,减小峰值硬度和延长欠时效时间;外加应力能够促进Al-Cu-Mg-Ag合金中θ′相的析出,抑制Ω相的析出和长大;在外加应力的影响下,Ω相产生应力位向效应,且应力位向效应的产生主要在Ω相的形核阶段形成。     

Al-Zn-Mg-Cu-Zr合金型材的回归再时效析出行为研究

采用拉伸试验、硬度测试、电导率测试和透射电镜分析等方法研究了Al-Zn-Mg-Cu-Zr合金型材在180℃回归再时效阶段的析出行为。结果表明,合金在回归处理开始阶段,大部分的GPI区和部分尺寸细小的η’相迅速回溶到基体,合金的强度和硬度值降低至最小值;随着回归时间的延长,晶内析出了高温稳定性更好的η’相和GPII区,合金的强度和硬度值升高;进一步延长回归处理时间,合金中部分的η’相开始转变为η相,合金的强度和硬度值略有下降。再时效阶段,合金在较低的温度继续析出GPI区和较小尺寸的η’相,合金的强度和硬度值小幅增大。     

铈对Al-Cu-Mg-Mn-Ag合金时效析出与显微组织的影响

通过铸锭冶金及形变热处理,制备了不同铈含量的Al-Cu-Mg-Mn-Ag合金。采用金相观察、差热分析、扫描电镜及透射电镜研究了添加铈对合金的时效析出过程及显微组织的影响。结果表明：添加铈能显著细化铸态合金的晶粒,使平均晶粒尺寸由93μm减小至30μm,还可以加速挤压态合金的时效硬化过程,提高硬化水平,使最大硬度提高10%以上;此外,添加铈可缩短合金的峰时效时间,降低主要强化析出相—Ω相的析出温度,同时,也降低？相的直径,提高其析出体积分数及其在200～300℃时的高温热稳定性。     

循环时效对Ni_(75)Al_(7.5)V_(17.5)合金微观组织的影响

基于微观相场动力学模型,研究了Ni75Al7.5V17.5合金循环时效过程的沉淀相形貌演化,并与单级时效过程进行了比较.发现DO22相的溶解度随温度变化较L12相大:通过循环时效可以使粗大细长的L12相发生分断,从而达到细化沉淀颗粒的目的,使不规则的L12相发生球化;还分析了发生分断和球化的原因.     

Al-Si-(Cu,Mg)合金时效析出相分析

测定了Al-7Si-0.3Mg和Al-4.5Cu合金的时效硬化曲线,结合DSC分析、TEM分析和金相组织分析,研究了两种合金的时效析出过程.结果表明:两种合金的时效硬化曲线均出现了“双峰”现象,第二个峰稍大于第一个峰.两种合金首先发生过饱和固溶体向GP区转化,然后发生GP区向θ(Al2Cu)转化或者是GP区向β(Mg2Si)转化的过程.Al-7Si-0.3Mg合金在时效4h后的析出相是Mg2Si,Al-4.5Cu合金时效析出相是Al2Cu相.     

微量Sc对2195铝锂合金应变时效态的显微组织和力学性能的影响

采用拉伸试验机、光学金相显微镜、透射电镜、扫描电镜等设备研究了添加微量Sc对2195铝锂合金应变时效态的显微组织和拉伸性能的影响。结果表明：微量Sc加入后能生成细小弥散Al3(Sc，Zr)质点，起到抑制再结晶的作用；微量Sc的加入既促使合金晶内析出的T1相分布更弥散均匀，又能使亚晶界和晶界上析出的T1相变得细小，几乎不出现明显的晶界无析出带，因而可在不降低合金强度的前提下有效地改善其塑性。     

Effects of Sc content on the mechanical properties of Al-Sc alloys

The effects of Sc content on the mechanical properties of Al-Sc alloys were investigated. The results show that the strengths of all the tested alloys with 0.1 wt.%, 0.3 wt.%, and 0.4 wt.% Sc additions increase initially with an increase in annealing time, due to the increase in volume fraction and size and the decrease in particle interspacing of Al₃Sc particles. After reaching peak values, the strengths of all the tested alloys start to decrease with increasing annealing time due to the coarsening and increase in particle interspacing of Al₃Sc particles. It has also been shown that the alloy with 0.3 wt.% Sc has a higher strength and a lower elongation than the alloys with 0.1 wt.% and 0.4 wt.% Sc. The increase in strength and the decrease in elongation of the alloy with 0.3 wt.% Sc are due to the smaller particle interspacing of Al₃Sc particles, resulting in a strong inhibition of dislocation movement during deformation.     

稀土铒对Al-Cu-Mg-Ag-Zr合金微观组织与时效行为的影响

研究了稀土元素铒对Al-Cu-Mg-Ag-Zr合金微观组织以及165℃时效特性的影响.力学性能测试结果表明:合金中添加稀土Er对合金的强度贡献不大,但可大幅度提高合金的塑性变形能力.显微组织分析表明:添加稀土Er主要以Al8Cu4Er相和少量固溶于基体的形式存在于合金中,Al8Cu4Er相在合金变形过程中细化,对合金起到异质强化的作用.合金中Er原子和空位发生强交互作用,阻碍Ag、Mg原子团的形成,抑制了Ω相形核,延迟Al-Cu-Mg-Ag-Zr合金在165℃人工时效响应.     

Correlation between microstructure and corrosion behaviour of Bi-Zn solder alloys

ABSTRACT

Bi-Zn solder alloys with different Zn contents (1.5, 2.7 and 5wt-%) were prepared by casting and the correlation between the microstructure and corrosion behaviour by mean of direct current electrochemical tests was studied. The surface analysis of the hypoeutectic Bi-Zn alloy samples revealed the presence of needle-like ZnO and very small agglomerated spherical particles. By contrast, eutectic alloy presented the formation of a uniform and compact film of ZnO, which is related to the better distribution of Zinc in the Bi-rich matrix. Despite the increase in Zn content compared to the hypoeutectic alloy, the corrosion rate showed similar values regardless of its content in the alloy. The Bi-5wt-% Zn alloy presented the highest limiting current density, and consequently, the highest degree of corrosion of the studied alloys. The pro-eutectic phase consisting of large and thick Zn fibres is preferentially dissolved, promoting a selective attack that penetrates inside the sample.     

Effects of minor Sc on the microstructure and mechanical properties of Al-Zn-Mg-Cu-Zr based alloys

Five kinds of Al-Zn-Mg-Cu-Zr based alloys with different Sc additions were prepared by ingot metallurgy. The effects of minor Sc on the microstructure and mechanical properties of Al-Zn-Mg-Cu-Zr based alloys were investigated using tensile tests, optical microscopy (OM), and transmission electron microscopy (TEM). The results show that the ultimate tensile strength and yield strength are improved by 94 and 110 Mpa, respectively, and the elongation to failure remains at a reasonable extent (11.1%) in the Al-Zn-Mg-Cu-Zr based alloy with 0.21 wt.% Sc addition after solution heat treatment at 475℃ for 40 min and then aged at 120℃ for 24 h. The addition of minor Sc induces the formation of Al3(Sc,Zr) particles, which are highly effective in refining the cast microstructures, retarding recrystallization, and pinning dislocations. The increment of strength is attributed mainly to fine grain strengthening, precipitation strengthening of Al3(Sc,Zr) particles, and substructure strengthening.     

Precipitation during homogenization cooling in AlMgSi alloys

Precipitation during the industrial cool down takes place predominantly above 300 °C in the EN AW-6082 and 6005 alloys. The phase precipitation throughout cooling is equilibrium β phase. A considerable capacity is retained after the cool down for further precipitation during a subsequent heating cycle. The β-Mg₂Si is once again the predominant phase that forms during a scan heating cycle employed in exactly the same manner with the industrial billet preheating operation. The precipitation in the 6060 alloy, on the other hand, occurs predominantly below 300 °C with additionally β′-Mg₂Si particles formed below 200 °C.     

Effect of 0.3% Sc on microstructure,phase composition and hardening of Al-Ca-Si eutectic alloys

The phase composition, microstructure and hardening of aluminum-based experimental alloys containing 0.3% Sc, 0–14% Si and 0–10% Ca (mass fraction) were studied. The experimental study (electron microscopy, thermal analysis and hardness measurements) was combined with Thermo-Calc software simulation for the optimization of the alloy composition. It was determined that the maximum hardening corresponded to the annealing at 300–350 °C, which was due to the precipitation of Al₃Sc nanoparticles with their further coarsening. The alloys falling into the phase region (Al)+Al₄Ca+Al₂Si₂Ca have demonstrated a significant hardening effect. The ternary eutectic (Al)+Al₄Ca+Al₂Si₂Ca had a much finer microstructure as compared to the Al–Si eutectic, which suggests a possibility of reaching higher mechanical properties as compared to commercial alloys of the A356 type. Unlike commercial alloys of the A356 type, the model alloy does not require quenching, as hardening particles are formed in the course of annealing of castings.     

Al-Cu-Zr和Al-Cu-Zr-Ti-V合金中Al_3Zr析出相的析出行为

利用透射电子显微技术研究Al-Cu-Zr和Al-Cu-Zr-Ti-V合金中Al3Zr的沉淀析出行为。亚稳态的Al3Zr沉淀相在枝晶中心均匀形核并获得均匀分布。然而,在枝晶边缘区域的析出复杂,观察到由许多球形Al3Zr析出颗粒组成的螺旋状和条状的形貌。条状的沉淀团簇沿100铝方向优先排列,这可能与Al2Cu的亚稳态θ′和稳态θ析出相相关。添加铜有利于Al3Zr沉淀相从L12→D023的结构转变。     

Al-Mg-Sc中间合金的制备

在非真空条件下用氟化物熔盐体系镁 (铝 )热还原法制备了Al Mg Sc中间合金 ,讨论了金属还原剂的选择及还原温度、时间等工艺条件对钪收率的影响 ,并研究制定了氧化钪固相氟化制备氟化钪熔盐工艺。采用Al Mg合金熔体为还原剂经二次还原后钪收率 >80 %,制备的Al Mg Sc中间合金铸锭中钪含量 >1.9%,最佳的还原反应温度为 110 0K ,还原时间 40min .。氟化钪还原产生的初生态钪与铝作用形成稳定的Al3 Sc化合物 ,促进了还原的进行 ,使钪收率得到了大幅度提高。