Quantitative assessment of preferential fatigue initiation sites in a multi‐phase aluminium alloy

Complex multi‐phase Al–Sn–Si alloys are commonly employed in the manufacture of small automotive plain bearings. The fundamental fatigue initiation behaviour of this class of alloys is currently not well understood. A range of analytical techniques were applied to investigate preferential initiation site location and to attempt to identify critical microstructural features. It was apparent from experimental studies that points of fatigue crack initiation are associated with the Si secondary phase. Using tessellation approaches and subsequently both adaptive numerical modelling and micro‐scale finite element modelling allowed the identification of features affecting the probability that a given Si phase would initiate a fatigue crack.     

Structure of rapidly solidified aluminum alloys

This paper is a summary of an extensive research program carried out by the authors on the structure of rapidly solidified aluminum alloys; and a comparison with the work of others also involved in this field. The paper discusses the changes in the dendritic and non-dendritic structure of the matrix at cooling rates from 10^–3 to 10¹⁰ K/s and discusses the hetergeneity of the structure caused by interdendritic-segretion during solidification.     

镁基储氢材料的研究进展

本文回顾和总结了近几十年来，特别是近十年来镁基储氢材料的发展情况，重点综述了机械合金化Mg-Ni2合金体系的研究情况及其近期的进展，从储氢材料成份及配比，制造工艺改进以及材料的组织结构对材料性能的影响等各方面进行一定的分析和归纳，对储氢材料研究中出现的问题以及今后的发展方向都作了探讨。     

TiAl＋Sb合金的热稳定性的研究

研究了退火处理对Ｔｉ－３４ｗｔ．％Ａｌ－０．５ｗｔ．％Ｓｂ合金的室温抗弯性能，显微组织，相组成和断口形貌的影响。发现，低于１０００℃退火处理，ＴｉＡｌ＋Ｓｂ合金的显微组织没有变化，其力学性能仍然保持较高的值。此合金成分适应高温使用条件。     

SiGe:GaP合金的微观结构和温差电特性

经高温热处理后的 SiGe∶GaP 半导体温差电材料,其微观结构由具有富 Si 相特征变化成为具有富 Ge 相特征,温差电优值也得到了提高。实验还表明,材料晶格热导率的降低与富 Si 相的消失和富 Ge相的出现有关。然而,塞贝克系数和电导率的显著变化却与微观结构中富 Si 相和富 Ge 相的变化基本无关。通过对材料微观结构和温差电特性比较发现,具有富 Ge 相特征的微观结构对应于较大的温差电优值。     

铝锂合金力学性能的各向异性

针对当前困扰铝锂合金实际应用的各向异性问题，概述关于铝锂合金中各向异性的表现规律，产生机理及对于降低各向异性所采用的方法等方面的研究现状和进展，对铝锂合金各向异性表现与微观组织结构的关系以及目前克服各向异性所采用方法的局限性进行分析。就此提出，若彻底解决这一问题则必须采用更先进的合金化方法及热加工工艺，研制新一代铝锂合金的观点和研究方向。     

An investigation of pore cracking in titanium welds

Two welded Ti-6A1-4V pressure vessels leaked prematurely in service. The leaks were caused by cracks emanating from weld porosity. The cracks originated during fabrication, with subsequent growth in service leading to the formation of the leak paths. Pore cracking is thought to be caused by a mechanism that involves both sustained-load and cyclic contributions, with the former being the more prominent. It is shown that the tendency for cracking is influenced by pore position and that pore size is not a deciding factor in that regard. The factors that govern pore cracking are discussed, and the possible role of interstitial embrittlement is assessed.     

Al的添加对Gd-Co合金的影响

用X射线衍射、扫描电镜和磁性测量等方法研究了Al的添加对Gd-Co合金的影响。研究结果表明：在一定范围内掺杂Al导致GdCo2、GdCo5和Gd2Co17晶格常数增大，但仍保持各自的晶体结构；Al的添加使GdCo2和Gd2Co17的居里温度降低，但是对于GdCo2却是先增后减。该结论为寻找新的磁性材料提供了有价值的参考。     

Rapid determination of the fracture toughness of metallic materials using circumferentially notched bars

Three types of material whose fracture toughness tests were previously performed by using circumferentially notched bars, namely (1) a dual-phase steel with three different morphologies; (2) an Al-Zn-Mg-Cu-wrought alloy; and (3) Al-Si-cast alloys with three different Si contents, were investigated in terms of accuracy and reliability of the testing method. Also, the advantages of using circumferentially notched bars for fracture toughness determination of metallic materials were discussed. With the help of stress concentration factors, which are associated with the bluntness of the notch, correction factors for the fracture toughness calculations are derived. The corrected fracture toughness values are found to be close to the uncorrected ones, implying that the testing procedure is reliable.     

Oscillating Cup Viscosity Measurements of Aluminum Alloys: A201, A319 and A356

An oscillating cup viscometer was developed to measure the absolute viscosities of molten metals. Previous experiments established the capability of the apparatus to characterize the viscosities of molten nickel-based superalloys. However, modifications to the instrument and its theoretical analysis were required for reliable measurements on molten aluminum alloys, presumably due to their lower densities and lower viscosities. The theoretical literature for the fluid flow inside an oscillating cup is reviewed, and a working equation without any correction factor is developed for the improved viscometer. Some design parameters of the viscometer that directly affect the accuracy of viscosity estimation by using the working equation are discussed. A special vertical furnace was adopted to uniformly heat a longer cylindrical sample (10 mm inner diameter and 120 mm length) with a temperature difference of less than 2°C over the sample length. The measuring procedure was also improved to get more accurate motion parameters. It is estimated that the working equation and improved instrument provide an uncertainty of less than 4%. In addition, applications and experimental data are presented for pure aluminum and three aluminum alloys: A201, A319, and A356.