La Peiqing

EFFECTS OF Al ELEMENT ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF HOT-ROLLED 316L STAINLESS STEEL

316L stainless steel is applied to high-temperature environment because of an attractive combination of mechanical properties and corrosion resistance in various aggressive environment. However,the corrosion resistance of 316L was reduced in a particular environment such as water vapor, aggressive sulfur gas which was attributed to the Cr_2O_3 protective scales formed in 316L.The Cr_2O_3 scales are compromised by water vapor due to the formation of volatile Cr oxy-hydroxide species. The Al_2O_3 is more thermodynamically stable in these enviroment than Cr_2O_3.In this work,the effects of Al element on the microstructure,mechanical properties and corrosion resistance of hot-rolled 316L were investigated.Microstructure evolution was observed by OM,EPMA and XRD.Mechanical properties were measured by tensile tests.The resistances to intergranular and uniform corrosion of hot-rolled 316L with different Al content were investigated by means of soaking method at 65%HNC_3 and 5%H_2SO_4,respectively.The results show that microstructure has changed from singleγtoα+γdouble phase.With the increase of Al content in 316L,the yield strength and ultimate tensile strength increased but the ductility decreased.The fracture morphology of tensile was observed by SEM.Which indicated that the fracture mechanism behaved in ductile fracture.Corrosion rate of intergranular and uniform corrosion decreased remarkly as the Al content increased.The optimum Al content in terms of corrosion rate curve was about 2%.Improvment of corrosion resistance was mainly due to Al_2O_3 scale formed in 316L.

稀释剂添加量对燃烧合成亚微米ZrB 2 微观组织的影响

Submicron ZrB2 powders were prepared by combustion synthesis using NaCl as the diluent and B2O3, Mg and ZrO2 as raw materials. The samples were analyzed by SEM, EDS, XRD and particle size analyzer. The results show that adiabatic temperature of the system decreases with the diluent content increase. The products are aggregates which contain a small amount of larger-sized particles and a large number of small-sized particles. The average particle size of products drops from 305 nm to 160 nm as the value of k, i.e. molar ratio of the diluent, increases from 0.5 to 1.5. The products after leaching mainly consist of ZrB2 and ZrO2, and the content of the latter decreases with the increase of k. NaCl plays very important roles, such as providing a liquid medium, promoting the mass transfer, improving the purity of the products, reducing the combustion temperature of the system, inhibiting growth of particles by giving a coating on the surface, and leading to small-sized particles.以NaCl为稀释剂, B 2 O 3 、ZrO 2 和Mg粉为原料, 利用燃烧合成法成功制备了亚微米ZrB 2 粉体, 并对其进行了SEM、EDS, XRD和粒度分析。结果表明: 随着稀释剂添加量增加, 体系绝热温度下降; 浸出产物是由少量的大尺寸颗粒和大量的小尺寸颗粒形成的弱团聚体; 稀释剂摩尔数k值从0.5增加到1.5时, 产物平均颗粒尺寸从305 nm降低到160 nm; 产物浸出后主要物相为ZrB 2 和ZrO 2 , 后者含量随稀释剂添加量增加而降低。稀释剂可以提供液态介质, 促进质量传输, 提高产物纯度, 还可以降低体系燃烧温度, 并包覆在产物表面抑制其结晶长大, 降低颗粒尺寸。以NaCl为稀释剂, B 2 O 3 、ZrO 2 和Mg粉为原料, 利用燃烧合成法成功制备了亚微米ZrB 2 粉体, 并对其进行了SEM、EDS, XRD和粒度分析。结果表明: 随着稀释剂添加量增加, 体系绝热温度下降; 浸出产物是由少量的大尺寸颗粒和大量的小尺寸颗粒形成的弱团聚体; 稀释剂摩尔数k值从0.5增加到1.5时, 产物平均颗粒尺寸从305 nm降低到160 nm; 产物浸出后主要物相为ZrB 2 和ZrO 2 , 后者含量随稀释剂添加量增加而降低。稀释剂可以提供液态介质, 促进质量传输, 提高产物纯度, 还可以降低体系燃烧温度, 并包覆在产物表面抑制其结晶长大, 降低颗粒尺寸。