A new method of manufacturing tubes with nano/ultrafine grain structure by stagger spinning and recrystallization annealing is proposed in this study. Two methods of the stagger spinning process are developed, the corresponding macro forming quality, microstructural evolution and mechanical properties of the spun tubes made of ASTM 1020 steel are analysed. The results reveal that a good surface smoothness and an improved spin-formability of spun parts can be obtained by the process combining of 3-pass spinning followed by a 580 ºC× 0.5 h static recrystallization and 2-pass spinning with a 580 ºC×1 h static recrystallization annealing under the severe thinning ratio of wall thickness reduction. The ferritic grains with an average initial size of 50 m are refined to 500 nm after stagger spinning under the 87% thinning ratio of wall thickness reduction. The equiaxial ferritic grains with an average size of 600 nm are generated through re-nucleation and grain growth by subsequent recrystallization annealing at 580 ºC for 1-hour heat preservation. The tensile strength of spun tubes has been founded to be proportional to the reciprocal of Layer Spacing of Pearlite (LSP), and the elongation is inversely proportional to the reciprocal of LSP. This study shows that the developed method of stagger power spinning has the potential to be used to manufacture bulk metal components with nano/ultrafine grain structure.

Laser conditioning is an effective method to improve the laser damage threshold of HfO 2 /SiO 2 multilayer films prepared by electron beam evaporation. In this paper, some parameters that can affect the efficiency of laser conditioning were discussed. The result is that the maximum conditioning fluence should be less than 90% of its unconditioned laser induced damage threshold (LIDT) to avoid damage to the film. The laser beam increment between pulses and laser conditioning steps has a great influence on the improvement of damage threshold of HfO 2 /SiO 2 multilayer high reflective coatings. The coverage of the light intensity on the defect should be as wide as possible, and the irradiation of light intensity should be as high as possible. The main mechanisms of laser conditioning of HfO 2 /SiO 2 multilayer high reflective coatings may be the removal of Hf, Si and O ions and the removal of the defects in the films.

ABSTRACT

Abstract. In order to reduce the environmental pollution caused by the three wastes during the process of electroplating of gold-like film on stainless steel, in this paper, the "vacuum evaporation and annealing" composite technologies were adopted to evaporate gold-like film in 16 stainless steel 304 substrates, and electronic color cards and color software were also used for analyzing the color and luster of the gold-like film. Experiments shows that the negative pressure, annealing temperature and mass fraction of the double copper alloys have influence on preparation of imitation in assaying the fineness of gold film, the annealing temperature has significant effects on imitation in assaying the fineness of gold film.

Recrystallization is a key step while conducting the composite process of severe extruding and heating treatment for fabricating the ultrafine-grained parts, howerer, the heating temperature palys a vital role that it directly effects the metallographic structure of extruded workpiece. In order to reveal the effects of heating temperature on metallographic structure of the extruded workpieces,three kinds of samples with different reduction ratio were put into the heating furnace when the temperature in frunace is over the recovery temperature of C-Mn extruded workpiece(about 450 °C), that is to shorten the temperature-rising time,thus the nucleation rate was increased simultaneously by doing so. During the heating process, the time-constant & temperature-varying together with time-varying & temperature-constant experimental scheme were adopted for different samples. Finally by measuring the hardness and analyzing the micro structures of C-Mn extruded workpiece, it can be concluded that fully recrystallization occurs in No.3 extruded workpiece with the condition of heating for 1 hour at 580 °C and cooled in the furnace, its average size is about 1 um.