稀土双相永磁合金X射线无标定量相分析

通过对Ｎｄ２Ｆｅ１４Ｂ四方相单胞分析，确定其各原子坐标，进而采用计算Ｋ值直接对比法，建立了双相永磁合金相分析计算程序。在对单相计算结果与实验值取得一致的基础上，对α－Ｆｅ／Ｎｄ２Ｆｅ１４Ｂ实验合金进行了相含量测算和分析。     

半固态ZnAl27合金挤压成形金相组织研究

对常规ZnAl2 7合金和经机械搅拌得到的半固态ZnAl2 7合金材料进行了挤压成形试验 ,分析了合金在挤压成形后得到的试件的金相组织。结果表明 ,半固态ZnAl2 7合金挤压成形件的组织极为均匀细小。     

高熵合金及其相关复合材料的粉末冶金综述

High-entropy alloys (HEAs) have attracted increasing attention because of their unique properties, including high strength, hardness, chemical stability, and good wear resistance. Powder metallurgy is one of the most important methods used to fabricate HEA materials. This paper introduces the methods used to synthesize HEA powders and consolidate HEA bulk. The phase transformation, microstructural evolution, and mechanical properties of HEAs obtained by powder metallurgy are summarized. We also address HEA-related materials such as ceramic–HEA cermets and HEA-based composites fabricated by powder metallurgy.     

Effect of Zr addition on the stability of precipitated Laves phase and mechanical properties of Fe–Cr–Al-based alloys at high temperatures

The effect of a small amount of Zr addition on the temperature-dependent stability of Laves phase particles and mechanical properties of Fe-13.5Cr-4.73Al-2.07Mo-(0.34–0.5)Nb-(0.65–0.98)Ta-(0–0.33)Zr (wt. %) ferritic alloys was investigated in the present study. The designed alloy ingots were hot-rolled, aged at 1073 ?K for 24 ?h, and then re-treated at 1273 ?K, 1323 ?K, 1373 ?K, and 1473 ?K for 1 ?h, respectively. It was found that the Zr addition could not only stabilize the Fe₂M Laves phase (M ?= ?Mo,Nb,Ta,Zr) to a much higher temperature, but also induce the formation of stable Fe₂₃Zr₆ phase. The high-temperature (HT) microstructural stability of the alloys significantly was improved, as evidenced by the fact that a certain amount (0.66–1.19%) of precipitates (Fe₂M, Fe₂₃Zr₆, and core(Fe₂₃Zr₆)-shell(Fe₂M)-structured particles) with an appropriate size (～1.0 ?μm) uniformly distributed in the ferritic matrix even after being re-treated at 1473 ?K. Particularly, the formation of core-shell-structured particles at HTs was studied from the viewpoint of both solid solubility and diffusion coefficient of M in the matrix. All these aged alloys exhibited prominent mechanical properties at both room and elevated temperatures, showing high yield strength with σ_YS ?= ?490–560 ?MPa at room-temperature and σ_YS ?= ?80–85 ?MPa at 1073 ?K. The strengthening effect was further discussed in light of various strengthening mechanisms, and the calculated strength are in good agreement with the experimental results.     

Sn及Sn合金的微观断裂行为

微电子系统中互连尺寸的微细化使构成焊点的钎料合金的力学性能成为影响电子封装与组装产品可靠性的关键因素。因此,在微米及纳米尺度深刻掌握Sn基钎料合金的断裂行为对于更好地预测焊点可靠性具有重要意义。本文针对100Sn、63Sn37Pb、96.5Sn3.5Ag三种Sn及Sn合金,在进行力学性能测试和显微组织分析的基础上,考察了Sn及Sn合金在微米尺度上的动态断裂机制,以及纳米尺度上裂纹尖端的真实物理过程,阐述了Sn基体、含铅Sn合金和无铅Sn合金三者互有关联又各有不同的微观断裂行为特征。     

Preparation of Al<Subscript>72</Subscript>Ni<Subscript>8</Subscript>Ti<Subscript>8</Subscript>Zr<Subscript>6</Subscript>Nb<Subscript>3</Subscript>Y<Subscript>3</Subscript> amorphous powders and bulk materials

Amorphous Al₇₂Ni₈Ti₈Zr₆Nb₃Y₃ powders were successfully fabricated by mechanical alloying. The microstructure, glass-forming ability, and crystallization behavior of amorphous Al₇₂Ni₈Ti₈Zr₆Nb₃Y₃ powders were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). The isothermal crystallization kinetics was analyzed by the Johnson–Mehl–Avrami equation. In the results, the supercooled liquid region of the amorphous alloy is as high as 81 K, as determined by non-isothermal DSC curves. The activation energy for crystallization is as high as 312.6 kJ·mol?1 obtained by Kissinger and Ozawa analyses. The values of Avrami exponent (n) imply that the crystallization is dominated by interface-controlled three-dimensional growth in the early stage and the end stage and by diffusion-controlled two- or three-dimensional growth in the middle stage. In addition, the amorphous Al₇₂Ni₈Ti₈Zr₆Nb₃Y₃ powders were sintered under 2 GPa at temperatures of 673 K and 723 K. The results show that the Vickers hardness of the compacted powders is as high as Hv 1215.     

铝合金变形抗力的实验研究

采用恒应变速率凸轮式形变压缩试验机试验了四种铝合金材料的变形抗力 ,分析了应变率和应变速率对变形抗力的影响 ,结果表明随应变的增加 ,变形抗力以近似幂函数关系增加 ,在此基础上建立了简单、适用的变形抗力计算模型     

铝合金热塑性变形流动应力及其数学模型

采用恒应变速率凸轮式压缩试验机，测定了４种铝合金材料在热状态下的流动应力，分析了应变率，应变速率及变形温度对流动应力的影响规律，通过对多种结构型式流动和数学模型的回归分析比较，确定了计算精度较高，结构型式较简单，适合于现场计算机在线控制和工程计算的数学模型。     

磨粒和抛光垫对铝合金化学机械抛光性能

磨粒和抛光垫为化学机械抛光(CMP)提供了重要的机械磨削作用。为了探讨磨粒和抛光垫对铝合金化学机械抛光的磨削作用,研究了不同种类磨粒和抛光垫对材料去除率和表面形貌的影响。结果表明：在pH=12-13时,氧化铝抛光液去除率(MRR)为910nm/min,远大于二氧化硅与氧化铈抛光液,且获得较为理想光滑表面。3种不同抛光垫抛光后的铝合金表面,呢子抛光垫表面将不会出现划痕与腐蚀点,表面粗糙度较低为10.9nm。随着氧化铝浓度的增加,材料去除率(MRR)和表面粗糙度(Ra)均增加。当氧化铝含量为4wt%时,抛光垫使用呢子抛光垫适宜铝合金化学机械抛光,在获得高去除率的同时铝合金表面精度高。     

纯钛滚压形变强化的研究

采用TEM,XRD技术研究了多晶纯钛滚压形变强化疲劳前后的显微组织特征和残余应力.实验结果发现:多晶纯钛疲劳抗力的提高主要是由于形变显微组织和残余压应力的产生及表面粗糙度的降低.滚压组织中形成高密度位错和单个?分散的变形孪晶,历经106以上的循环周次后,孪晶-晶界的交互作用是其主要特征.疲劳后次表面残余压应力松弛较表面严重.