Reinhard L■ck(Max-Planck-Institut fur Metallforschung
,
Institut fur Werkstoffwissechaft
,
Seestraβe 75
,
D-70174 Stuttgart
,
Germany)
材料科学技术（英文）
For a few years it has been realized that nanocrystalline phases can be formed during crystallization of amorphous alloys annealed isothermally below the crystallization temperature of usual heating experiments. Data of this transformation monitored by the measurement of magnetic susceptibility are presented. A method using a magnetic balance with electronic stabilisation and combined computer facilities is applied. Constant heating and cooling rates as well as isothermal heat treatments are used. Magnetic measurements are able to detect the onset of the transformation of amorphous Ni-P alloys much earlier than was possible with differential scanning calorimetry. The transformation kinetics can be analyzed by means of the Avrami plot based on the Johnson-Mehl-Avrami equation.The kinetics of solid state reactions in the nanostructured material can be investigated similarly. Formation of a Ni-phase in a nanostructured Hf-Ni alloy could be detected in a very early stage, where calorimetric methods are not sensitive. Segregation phenomena could be detected from the experiments even after long time. The sensitivity of the applied method is not dependent on the heating rate as the sensitivity of scanning calorimetry is
关键词:
A.R. Kiani-Rashid
材料科学技术（英文）
The purpose of this study was to determine the influence of heat treatment cycle on graphite phase formation on CK 45 steel. The presence of well distributed graphite in the matrix is responsible for the good mechanical and thermal properties of this kind of alloy. Such properties include excellent wear resistance, higher resistance to thermal shock, and higher resistance to oxidation at high temperature. A number of specimens were made up of appropriate design to provide the experimental materials. The transformation phase to a free carbon microstructure during graphitization under different conditions was then examined for the most successful experimental steels. Austenitising temperature of 920°C and the following isothermal heat treatment of 750°C at different holding times were used. Microstructures were examined by OM (optical microscopy) and SEM (scanning electron microscopy). Furthermore, it was found that isothermal transformation at 750°C for different soaking times produced a typical microstructure. Also, the amount of graphite increased with increasing isothermal heat treatment time. Heat treatment leading to supersaturation of iron with carbon was described and some of the consequences of the supersaturation were presented. Finally, the formation of the thermodynamically stable state of the graphite taken from the supersaturated solid solution was discussed.
关键词:
Graphitization
Ata Kamyabi-Gol
钢铁研究学报(英文版)
When processing parts made from medium carbon steel, toughness and flexibility are of importance. Therefore, to achieve these properties, the cementite in the steels is spheroidized through heat treatment. Different parameters such as the time and temperature of spheroidizing and the initial microstructure of the steel affect the amount of spheroidized cementite. In the present work, the percent of contribution of two parameters, i.e. initial microstructure and spheroidizing time, on the percent of spheroidization in CK60 steel was investigated using Taguchi robust design. Based on the number of parameters (two) and the number of their levels (four), a L16 orthogonal array, which consists of 16 experiments, was chosen. The initial microstructures consisted of Martensite (M), Coarse Pearlite (C. P.), Fine Pearlite (F. P.), and Bainite (B) and the chosen spheroidization times were 4, 8, 12, 16 hours. Spheroidizing was done at the constant temperature 700 oC. After spheroidizing was completed, the samples were prepared in order to view their microstructure under an optical microscope and to determine the spheroidized percent using MIP? (Metallographic Image Processing) software. It was found that the spheroidizing time had the most influence (58.5%) on spheroidized percent and the initial microstructure only had a 31.1% contribution. Finally, the instantaneous growth rate of the carbide was also deduced.
关键词:
Spheroidizing;Kinetics;Heat treatment;CK60;Taguchi
Scripta Materialia
Nb(4)AlC(3), a new compound belonging to the MAX phases, was discovered by annealing bulk Nb(2)AlC at 1700 degrees C. The crystal structure of Nb(4)AlC(3) was determined by combined X-ray diffraction, high-resolution transmission electron microscopy and ab initio calculations. It was reported that Nb(4)AlC(3) follows the Ti(4)AlN(3)-type crystal structure. The lattice constants are a = 0.31296 nm, c = 2.41208 nm and the atomic positions are Nb1 at 4f (1/3, 2/3, 0.0553), Nb2 at 4e (0, 0, 0.1574), Al at 2c (1/3, 2/3, 1/4), C1 at 2a (0, 0, 0) and C2 at 4f (2/3, 1/3, 0.1086). (c) 2007 Published by Elsevier Ltd. on behalf of Acta Materialia Inc.
关键词:
Nb(4)AlC(3);ceramics;crystal structure;thin-films;ti3sic2;ti4aln3;ta4alc3;microstructure;deformation;carbides;ti3alc2;growth
王苹梅柄初雷零
腐蚀学报（英文）
用热压的方法合成了若干MAX相化合物，包括相（Ti2AlC和Ti2AlN）和312相（Ti3SiC2和Ti3AlC2）;研究了它们在1 mol/L HCl、1 mol/L NaOH和1 mol/L H2SO4中的电化学性质及其结构与其稳定性的关系.结果表明:在所有溶液中,312型MAX相比211相更稳定;Ti3SiC2 和Ti3AlC2几乎在所有溶液里都发生钝化，而Ti2AlC和Ti2AlN在1 mol/L HCl中活跃地溶解，还伴有大量气泡产生；Ti3SiC2比Ti2AlC、Ti2AlN 和Ti3AlC2更稳定.
关键词:
MAX相
,
polarization curves
,
electrochemical behavior
王苹
,
梅炳初
,
雷零
腐蚀学报（英文）
doi:10.3969/j.issn.1002-6495.2009.01.014
用热压的方法合成了若干MAX相化合物,包括211相(Ti2AlC和Ti2AlN)和312相(Ti3SiC2和Ti3ALC2);研究了它们在1 mol/L HCl、1 mol/L NaOH和l mol/L H2SO4中的电化学性质及其结构与其稳定性的关系.结果表明:在所有溶液中,312型MAX相比211相更稳定;Ti3SiC2和Ti3AlC2几乎在所有溶液里都发生钝化,而Ti2AlN在1 mol/L HCl中活跃地溶解,还伴有大量气泡产生;Ti3SiC2比Ti2AlC、Ti2AlN和Ti3AlC2更稳定.
关键词:
MAX相
,
极化曲线
,
电化学性质
