A356合金细化处理效果的孕育和衰退

通过考察A356合金在静置过程中细化效果的变化，研究了亚共晶铝硅合金细化处理的孕育期和衰退期。细化处理的孕育期的形成是由于细化初期的溶质过冷度小造成的，随着溶质Ti含量的增加，溶质过冷度增大，从而激活更多的形核质点，限制枝晶生长；长时间静置后，尽管细化元素Ti含量基本不变，但是成分偏析倾向加剧，形核质点粗化并沉淀，有效核心减少，出现细化效果衰退；采用预细化合金锭可以缩短甚至消除细化处理的孕育期。     

稀土对过共晶Al-Si合金P变质效果的影响

研究了加入稀土元素La对P变质Al-18Si合金中Si的形态及尺寸的影响，结果表明：稀土元素La的加入优化了P的变质效果，在细化初晶Si的同时变质了共晶Si，并且明显减缓了P变质初晶Si的粗化趋势，使变质效果至少可维持6h以上，通过扫描电镜测定了稀土元素La在合金中的分布，并分析讨论了稀土元素La对P变质效果影响的机理和作用。     

镁合金废料的回收

在镁合金零部件生产过程中，特别是在压力铸造生产中，产生出来的废料以及使用后报废的镁合金零件逐渐增多。出于成本和环境因素的考虑，必须对这与日俱增的镁合金废料进行有效回收。本文以生产占90％的镁合金零部件压力铸造为主线，介绍镁合金废料回收的经济分析，镁合金废料的来源和分类、现行回收技术的现状及发展趋势。并介绍香港生产力促进局和重庆硕龙科技公司最近研究开发的一种新型镁合金废料现场精炼回收系统。     

大型异形铝铸件的铸造工艺研究

大型异形铝铸件,铸造工艺难度较大,常需依赖于丰富的生产经验辅之以计算机凝固模拟分析技术。针对不同的形状,制定相应的铸造工艺。对管体、轮毂、支腿垫块、螺旋桨等典型产品较为成熟的生产工艺进行介绍。通过对这些典型铸件的工艺案例进行分析,探讨大型异型铝铸件的铸造工艺设计方法。     

XPS investigations of electrochemically formed passive layers on Fe/Cr-alloys in 0.5 M H2SO4

Passive layers on Fe20Cr and Fe15Cr were prepared by anodic oxidation in 0.5 M H₂SO₄ and were investigated by X-ray photoelectron spectroscopy. The preparation of the sputter-cleaned samples and their transfer to the ultrahigh vacuum was performed under protection of purified argon without any contact to the laboratory atmosphere. The prepassive layer consists of a homogeneous film with Cr(III)hydroxide and Cr(III)-sulphate with a low content of Fe(II). In the passive potential range a bilayer structure with enrichment of Cr(III)-oxides with an outer hydroxide and an inner oxide part is formed. Iron exists only in a bivalent oxidation state. In the transpassive potential range a pronounced change of the layer composition was observed: The outer part of the transpassive layer is formed predominantly by Fe(III) species whereas the inner part still contains a strong enrichment of Cr₂O₃.     

大型铝合金叶片金属型铸造工艺分析

针对铝合金叶片的铸造缺陷，分析指出浇注位置、浇注系统设计、型腔排气和充型温度场是造成铸造缺陷的主要因素，据此，有针对性地提出了铸型倾斜、平浇竖冷、沿分型面开设排气槽、改变涂料层厚度以及调整凝固顺序等改进措施，其效果在生产中得到验证。     

Steric hindrance as a rate controlling step in stress corrosion cracking

The effect of steric hindrance in the stress corrosion cracking (SCC) of Ag-15Pd (a/o) in AgI forming solutions was studied at room temperature. The solutions used were 1 M KI at a potential higher than that of AgI formation, and iodine dissolved in different n-alcohols. It was found that Ag-15Pd (a/o) is susceptible to intergranular stress corrosion cracking in those solutions. The SCC susceptibility measured as percentage of elongation to rupture and crack propagation rate is related to the size of the active species. While in KI aqueous solutions, as well as in iodine saturated benzene or iodine saturated toluene, the rate controlling step (RCS) was the reaction at the tip of the crack, in alcoholic-iodine solutions, the diffusion rate of the iodine containing molecules became the RCS.     

冷却方式对Zn-Cu包晶合金微观组织的影响

对采用不同冷却速度、不同散热条件的铸型得到的Zn-2.98Cu包晶合金的微观组织进行了研究.研究表明:在常规的砂型和金属型铸锭中,其微观组织为ε相 η相基体;在具有定向温度梯度的铸锭中,得到了定向的ε相枝晶 η相基体和定向的层片状(ε η)组织;并对层片状组织做了进一步分析,得到的Zn-Cu包晶合金层片间距平均值λ=4.06μm.     

压铸镁合金在汽车方向盘上的应用研究

通过对SC6380客车方向盘生产所用镁合金系的选择、方向盘服役模型建立、弹性有限元分析、结构再设计、压铸工艺虚拟设计及数值模拟等步骤，初步探索了镁合金方向盘的开发过程，为倡导镁合金等新材料在方向盘上的合理应用提供了技术支撑平台，通过以上步骤能有效的缩短产品开发周期。     

Effect ofθ-alumina formation on the growth kinetics of alumina-forming superalloys

Alumina-forming ODS superalloys are excellent oxidation-resistant materials. Their resistance relies upon the establishment of a stable, slow-growing, and adherent -alumina. In the present investigation, these alloys exhibited unstable and relatively less adherent -alumina phase, which increased the oxidation rate in the transient stage and converted into -alumina in the later part of the exposure. The oxide-growth process was found to depend upon various parameters such as temperature, time, and presence of an active elecment in the superalloy. Characterization carried out by XRD, SEM/EDAX, and AES on oxidized ODS and non-ODS alloys demonstrated a significant influence of the active element, Y, on the transformation of - to -alumina. SIMS analysis of two-stage oxidation at 900°C for two different durations evidently showed that the change in the transport process is due to -to--alumina transformation. On the basis of these results, a new and consistent mechanism is proposed to explain the influence of -alumina and its transformation on growth kinetics and the effect of yttrium on the transformation leading to good scale adherence and oxidation resistance.