Microstructure and strengthening mechanism of Mg—5.88Zn—0.53Cu—0.16Zr alloy solidified under high pressure

Mg—5.88Zn—0.53Cu—0.16Zr (wt.%) alloy was solidified at 2—6 GPa using high-pressure solidification technology. The microstructure, strengthening mechanism and compressive properties at room temperature were studied using SEM and XRD. The results showed that the microstructure was refined and the secondary dendrite spacing changed from 35 μm at atmospheric pressure to 10 μm at 6 GPa gradually. Also, Mg(Zn,Cu)₂ and MgZnCu eutectic phases were distributed in the shape of network, while under high pressures the second phases (Mg(Zn,Cu)₂ and Mg₇Zn₃) were mainly granular or strip-like. The solid solubility of Zn and Cu in the matrix built up over increasing solidification pressure and reached 4.12% and 0.32% respectively at 6 GPa. The hardness value was HV 90 and the maximum compression resistance was 430 MPa. Therefore, the grain refinement strengthening, the second phase strengthening and the solid solution strengthening are the principal strengthening mechanisms.     

Hydrogen embrittlement behavior in interstitial Mn–N austenitic stainless steel

The susceptibility to hydrogen embrittlement behavior was investigated in an interstitial Mn–N austenitic steel HR183 and stainless steel 316L. Hydrogen was introduced by cathodic hydrogen charging at 363 K. HR183 has stronger austenite stability than 316L despite its lower nickel content, the addition of manganese and nitrogen inhibited martensitic transformation during the slow strain rate tensile deformation. Due to the diffusion of hydrogen being delayed by the interstitial solution of nitrogen atoms and the uniform dislocation slips, hydrogen permeates more slowly in HR183 than 316L, contributing to an 84.79 μm thinner brittle fracture layer in HR183 steel. Hydrogen charging caused elongation losses in both 316L and HR183 steels associated with the hydrogen-enhanced localized plasticity (HELP) and hydrogen-enhanced decohesion (HEDE) mechanism. However, the hydrogen embrittlement susceptibility of HR183 is 3.4 times lower than that of 316L according to the difference in elongation loss between the two steel after hydrogen charging. Deformation twins trapped a lot amount of hydrogen leading to brittle intergranular fracture in 316L. The multiple directions of slip in HR183 steel suppressed the strain localization inside grains and delayed the adverse effects conducted by HELP and HEDE mechanism, eventually inhibiting server hydrogen embrittlement in the HR183 steel. This study is assisting in the development of low-cost stainless steel with excellent hydrogen embrittlement resistance that can be used in harsh hydrogen-containing environments.     

纳米陶瓷刀具材料的力学性能研究

纳米复相陶瓷刀具材料的研究成功有望从根本上解决陶瓷材料的脆性问题,比传统陶瓷刀具材料,它具有更高的抗弯强度、断裂韧度等力学性能。介绍纳米复相陶瓷的增韧补强机理,对研制高性能纳米陶瓷刀具材料需考虑的主要因素进行了探讨。     

稀土优化WC—Co硬质合金强韧性机理

探讨了稀土强化ＷＣ－Ｃｏ硬质合金的机理。结果表明，适量添加稀土氧化物或混合稀土氧化物均能有效提高ＷＣ－Ｃｏ硬质合金的强韧性；稀土能明显提高ＷＣ－Ｃｏ合金制品的表面宏观压应力：鉴于未加稀土的普通ＷＣ－Ｃｏ合金室温下ｈｃｐ型γ相的固有比例通常就很少，加稀土阻止γ相的ｆｃｃ→ｈｃｐ相变对合金强韧性的优化作用甚微；稀土氧化物对ＷＣ－８Ｃｏ硬质合金显微结构无明显影响，也不引起钨溶质对γ相的附加固溶强化效果。     

Estimate of stress state in rock masses adjacent to open pit walls

It is proposed to study the action exerted by the tectonic stresses on stability of open pit walls by using the method of core disking in exploratory holes and the tectono-physical method based on the analysis of tectonic structure of a rock mass. __________ Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 3, pp. 36–44, May–June, 2007.     

T1相(Al2CuLi)对铝锂合金各向异性的贡献

在分析T1相基本特性的基础上，结合相关工作，论述T1相与位错的交互作用、T1相与结构的相互影响、T1相对合金各向异性的贡献及稀土Ce的作用。结果表明，T1相因其分布及形貌而难以有效阻碍共面滑移；T1相对形变织构的形成起调整作用；织构的存在使T1相的分布及其与位错的作用发生变化，从而使其强化贡献具有各向异性。Ce影响形变织构的形成和合金的时效析出，并对共面滑移具有双重作用，从而改变T1相强化的各向异性。     

土壤固化类材料及其应用

综述了土壤固化剂的应用现状及其分类与加固机理,并总结出现阶段固化剂应用所存在的问题,提出了应开发基于土体细观结构不扰动加固技术。     

高压旋喷注浆在桥梁桩基补强中的应用

根据缺陷桩基拟加固的实际情况,在综合考虑多方面因素后,采用了高压旋喷注浆法对其进行加固补强。介绍了高压旋喷注浆法加固补强设计方案及施工流程。     

用压力灌浆法处理新近堆积黄土地基实例

本文主要介绍了用压力灌浆法处理山西某电厂黄土地基事故的情况,涉及灌浆加固机理、方法和试验灌浆等.加固工程结果表明,地基的湿陷性已消除,沉降量已控制在允许的范围之内.     

声波透射法在工程质检中的应用

该文以广州市广园立交系统桩基工程为例 ,介绍用声波透射法探测混凝土灌注桩严重缺陷位置 ,并对严重缺陷位置进行多次灌浆补强的效果进行检测分析与评价。