Su Xuping

THERMODYNAMICAL AND KINETIC INVESTIGA-TION OF FORMATION OF PERIODIC LAYERED STRUCTURE IN TiCu/Zn INTERFACE REACTION

The discovery of the periodic layered structure has been concerned over the past years. However, the exact formation mechanism of the structure is still in dispute for the lack of powerful evidence. The TiCu/Zn diffusion couples annealed at 390 or 450 °C were experimentally investigated in the present work. Three kinds of periodic layers exist in the diffusion regions. The thickness of the g+TiZn3 layers decreased with the annealing temperature but was not affected by the annealing time. All the observed phenomena were well interpreted based on the diffusion thermodynamics, kinetics and diffusion path theory. In the TiCu/Zn diffusion couple, the reaction is mainly controlled by the diffusion of Zn atoms towards the TiCu substrate. TiZn3 forms firstly at the boundary of the TiCu substrate and the diffusion region. And the Ti atoms diffuse through the g layer or the Cu atoms through the TiZn3 layer are difficult. Therefore, the g layer is formed by the short-range diffusion and the concentration of the Cu atoms. The cycle repeats and the diffusion path oscillates in the g+TiZn3 two-phase region, which results in *国家自然科学基金项目51171031和51201023资助 收到初稿日期: 2013-11-27,收到修改稿日期: 2014-03-14 作者简介:吴长军,男, 1985年生,讲师,博士 DOI: 10.11900/0412.1961.2013.00771 第930-936页 pp.930-936

Fe-Al-Cr合金在含锌蒸汽的低氧压中预氧化后的表面形貌

在900、950和1 000 ℃含Zn蒸汽的低氧压下对4种Fe-Al-Cr合金进行了预氧化实验，时间为1~5 h。Zn/ZnO粉末加热后提供的氧压在10 −21 ~10 −18 MPa之间。结果表明：经1 000 ℃预氧化1 h，Fe-1.2Al-2Cr合金表面的组织是ZnM 2 O 4 (M∶Al+Cr)+ZnO+α-Fe，Fe-2Al-3Cr及Fe-3Al-4Cr合金的表面组织是ZnM 2 O 4 +α-Fe，Fe-3Al-6Cr合金的组织是ZnM 2 O 4 +M 2 O 3 。合金中随Al、Cr元素少量的增加，表面氧化物增加，其中的Al含量快速增加；表面褶皱程度降低，突出的α-Fe相数量减少，向圆粒状转变。延长预氧化时间与提高预氧化温度都可以使表层的α-Fe相减少，氧化物面积增加。Zn在试样表面分布均匀，会渗入α-Fe相，会与表层的铝铬氧化物反应生成ZnM 2 O 4 相。

Study on Strengthening and Toughening Mechanisms of Aluminum Alloy 2618-Ti at Elevated Temperature

Abstract The tensile properties of the alloy 2618 and 2618-Ti were tested using a tensile testing machine. The morphologies of the fracture of tensile samples were observed using scanning electron microscopy. The strengthening and toughening mechanisms of alloy 2618-Ti at elevated temperature were systematically investigated based on the analyses of experimental results. The results showed that the tensile strength of alloy 2618-Ti is much higher than that of alloy 2618 at the temperature range of 250 and 300 °C. But the elongation of alloy 2618-Ti is much higher than that of alloy 2618 at the temperature range of 200 and 300 °C. The equal-strength temperature of intragranular and grain boundary of alloy 2618-Ti is about 235 °C. When the temperature is lower than 235 °C, the strengthening of alloy 2618-Ti is ascribed to the strengthening effect of fine grains and dispersed Al3Ti/Al18Mg3Ti2 phase. When the temperature is higher than 235 °C, the strengthening effect of alloy 2618-Ti is mainly attributed to the load transfer of Al3Ti and Al18Mg3Ti2 particles. The toughening of alloy 2618-Ti at elevated temperature is mainly ascribed to the fine grain microstructure, excellent combination between matrix and dispersed Al3Ti/Al18Mg3Ti2 particles as well as the recrystallization of the alloy at elevated temperature.

机械能助Al-Zn-Cr共渗工艺及渗层组织

采用机械能助渗技术，在600℃温度下对20钢进行Al-Zn-Cr共渗试验。利用光学显微镜、扫描电镜（SEM）、能谱仪（EDS）等仪器，分析合金元素铬对渗层组织共渗速率的影响，分析助渗时间对渗层组织的影响，测定铬在渗层中的分布，以及铬含量对渗层厚度的影响。结果表明：在机械能助Al-Zn-Cr共渗的研究中，铬含量的增加促进了渗层厚度的增加，而铬在渗层中分布相对均匀，无富集现象。在相同助渗时间下，铬含量的增加，促进了共渗速率的提高，促使渗层组织由单一的铁铝渗层组织转变为铁铝、铁锌多层渗层组织。在同一渗剂配比条件下，助渗时间的延长，促进Fe-Zn相形成，Fe-Al相减少。在助渗条件为600℃、3 h、5% Cr时，渗层为α-Fe（富锌）、Fe3Zn10、FeZn7、FeAl等相组成的多层组织，而且相对致密；渗层兼顾抗氧化性和阴极保护作用。