Tensile and Fracture Properties of 15 vol% SiC_p/2009Al Composites Fabricated by Hot Isostatic Pressing and Hot Extrusion Processes

15 vol% silicon carbide particle （SiCp）-reinforced 2009A1 matrix （15 vol% SiCp/2009A1） composites were fabricated by hot isostatic pressing （HIP） and hot extrusion processes. The tensile and fracture properties of 15 vol% SiCp/ 2009Al were studied. The results showed that hot extrusion increased the ultimate tensile strength （UTS）, yield strength （YS）, elongation （EL）, reduction in area （RA）, and fracture toughness of the composites. The heat treatment resulted in the increase in UTS, YS, and fracture toughness, but a decrease in EL and RA. Both hot extrusion and heat treatment had negligible effects on elastic modulus （E）. With the increase of SiCp size, the UTS, YS, and E decreased, but the EL and RA increased. The fracture toughness increased first and then decreased with increasing SiCp size, and when the SiCp size was about 7 μm, the composites obtained the maximum fracture toughness value of 31.74 MPa m^1/2.     

Microstructure Evolution During High-Temperature Deformation of 8090 Al-Li Alloy

The microstructure evolution of an as-processed 8090 Al-Li alloy during high temperature deformation has been investigated with emphasis on the dynamic grain size refinement and the formation of high-angle grain boundaries. Tensile tests were conducted at temperatures 470-560°C and initial strain rates of 10^-2-10^-6 s^-1. The starting and deformed samples were characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Electron Backscattered Diffraction (EBSD). The material showed a maximum elongation to failure of 660% at 530°C and strain rate of 10^-3 s^-1. A microstructural transformation from coarse grains to uniform fine microstructure through dynamic recrystallization (DRX) was observed. The DRX process was characterized by (1) a bimodal microstructure, (2) a gradual increase in average boundary misorientation angles, and (3) a gradual decrease of microtexture. The development of high angle boundaries was attributed to the absorption of dislocations into subboundaries and the grain boundary sliding (GBS)-induced subgrain rotation. The microstructural evolution was suggested to be responsible for the superplastic behavior observed in this as-processed material.     

绘制欲望 解读瓦尔斯温泉浴场的抵抗与制作

如今,建筑学中的诸多实践已经脱离了建造的物质活动,因此,建筑师必须采用多样的绘图方法,其中包括用于研究和探索建造方案的绘图。然而,他们的绘图工具和过程各异,结果也各异。将铅笔在图纸表面划过,不会自然地产生一根连续的线,而是一根变化的、可以在建筑师头脑中激发很多联想的线。更进一步说,空白纸张上每增加的一笔都记录了一个目的行为,并引导建筑师进入到眼前出现的图形结构与其头脑中图像的辩证思考中。致力于图像的绘制,可以引导建筑师们思考相应的建造,从而反驳设计者某些时候无节制的形式想象的野心。     

Mode I fracture toughness testing of eutectic Sn-Pb solder joints

The mode I plane strain fracture toughness of Cu/63Sn-37Pb solder joints was measured using a technique based upon the ASTM standard methods for fracture toughness testing. A solder joint compact tension sample geometry was selected for the evaluation and each sample was manufactured using a capillary soldering system that provides excellent control over critical processing parameters. The mode I plane strain fracture toughness based on these tests is 8.36 MPa√m. Failure is dominated by microvoid nucleation in the solder and fracture of the intermetallic particles that are located at the solder/copper interface. The validity of the testing method used and the relevance of the results to solder joint reliability are discussed.     

Tensile and Fracture Properties of 15 vol% SiCp/2009Al Composites Fabricated by Hot Isostatic Pressing and Hot Extrusion Processes

15 vol% silicon carbide particle (SiC_p)-reinforced 2009Al matrix (15 vol% SiC_p/2009Al) composites were fabricated by hot isostatic pressing (HIP) and hot extrusion processes. The tensile and fracture properties of 15 vol% SiC_p/2009Al were studied. The results showed that hot extrusion increased the ultimate tensile strength (UTS), yield strength (YS), elongation (EL), reduction in area (RA), and fracture toughness of the composites. The heat treatment resulted in the increase in UTS, YS, and fracture toughness, but a decrease in EL and RA. Both hot extrusion and heat treatment had negligible effects on elastic modulus (E). With the increase of SiC_p size, the UTS, YS, and E decreased, but the EL and RA increased. The fracture toughness increased first and then decreased with increasing SiC_p size, and when the SiC_p size was about 7 μm, the composites obtained the maximum fracture toughness value of 31.74 MPa m^1/2.     

用普通试验机测混凝土的断裂能GF

本文论述了如何用增加普通万能材料试验机刚度的方法来测量混凝土的断裂能GF;对试验机系统的刚度计算方法进行了探讨;指出了用于提高试验机刚度的刚性组件可采取的形式和在设计中应注意的几个问题;并进行试验验证。     

压铸镁合金AZ91D高周疲劳性能研究

研究了压铸镁合金AZ91D在应力比R=0．1条件下的高周疲劳性能。结果表明：AZ91D压铸镁合金的室温条件疲劳强度在应力比R=0．1时大约相当于其抗拉强度的44％；AZ91D合金内部的一些缺陷如夹杂等，容易引起应力集中，从而导致裂纹的萌生；AZ91D合金的疲劳断口可以观察到3个典型区域：疲劳源区、疲劳裂纹扩展区和瞬断区。疲劳裂纹扩展区的疲劳裂纹不明显，疲劳断口呈现出准解理断口的形貌。     

Influence of sintering temperature on microstructure and mechanical properties of WC-8Ni cemented carbide produced by vacuum sintering

The WC-8Ni powder was prepared by the ball milling method, then consolidated via a vacuum sintering technique. The influence of sintering temperature varying from 1375 °C up to 1500 °C on microstructure and mechanical properties of WC-8Ni cemented carbide was investigated. The best mechanical properties of the samples have been achieved at sintering temperature of 1450 °C. At which the relative density, hardness and fracture toughness (K_IC) of the samples are 99.81%, 13.23 GPa and 24.22 MPa m^1/2, respectively. The effect of η-phase identified by Murakami etching method and XRD technique on the mechanical properties was also discussed.