Influence Of Heat Treatment Time Research Articles

Recrystallization behavior of selective laser melted Co–Cr–Mo alloys with several heat treatment times

For parts manufactured by selective laser melting (SLM), post-heat treatment is essential to relieve residual stress. However, recrystallization and grain growth processes upon the stress-relieving heat treatment in SLM-fabricated Co–Cr–Mo alloys are not well understood. In this study, Co–Cr–Mo alloy specimens were fabricated by SLM and then heat treated at 1150 °C for various time periods (10, 20, 30, 45, and 60 min) to evaluate the influence of heat treatment time on the recrystallization process. The alloy microstructure was analyzed via confocal laser scanning microscopy, scanning electron microscopy combined with energy-dispersive X-ray spectroscopy, transmission electron microscopy (TEM), and electron backscatter diffraction (EBSD) and X-ray diffraction analyses. The mechanical properties of the produced specimens were evaluated by tensile tests. When the heat treatment was conducted for up to 45 min, the 0.2% yield strength (YS) decreased, whereas elongation increased. In contrast, when heated for 60 min, both the 0.2% YS and elongation decreased. The EBSD images demonstrated that both columnar and equiaxed grains existed, and recrystallization partially initiated after heating for 10 min. When heated for 45 min or more, the samples consisted entirely of equiaxed grains; however, TEM images showed regions with remaining subgrain boundaries and dislocations. Fully recrystallized microstructures were not obtained even after heating for 60 min. In addition, heat treatments longer than 60 min induced coarse grains and precipitates along the grain boundaries, which decreased the strength and ductility of the alloys. Retaining the subgrains within the grains to some extent enables producing alloys with excellent strength and ductility.

Fabrication of continuous carbon-fibers reinforced aluminum matrix composites and coating evolution during heat treatment

The nickel (Ni) was coated onto carbon fibers (CFs) through an electroplating process to enhance the infiltration of aluminum (Al) matrix to fiber. Moreover, these continuous CFs reinforced Al matrix (CF/Al) composites were fabricated via a twin-roll casting method. Here, the effects of rolling speed, pouring temperature and solidification times on the morphologies of CF/Al composites were discussed. The results show that the rolling speed of 4 rad/min provided excellent integrity between reinforcement and matrix. Moreover, solidification times of 60 s offered an effective balance between the heat transfer and infiltration. Furthermore, pouring temperature of 700 °C was advantageous to infiltrate Al matrix into fibers. In addition, the influence of heat-treatment time on coating evolution and property of the materials were discussed through microstructure evolution, phases composition and mechanical property tests. The results confirmed that composites with outstanding mechanical properties were acquired at the temperature of 600 °C for 160 min in a tube furnace. Hence, it is concluded that the twin-roll casting approach has great application prospects in the fabrication of CF/Al composites with high tensile properties.

Room temperature NO2 sensing properties of ZnO1-α coating prepared by hydrogen reduction method

NO2 emission is currently one of the important factors threatening the quality of life of residents. Preparing ZnO-based gas sensors to monitor the concentration of NO2 has attracted growing attention. This article reports a method for preparing ZnO1-α by hydrogen heat treatment. The ZnO coating prepared by the spin coating method is directly placed in a reduced atmosphere with 3% hydrogen for heat treatment to produce a self-doped ZnO1-α coating with oxygen vacancies, which can effectively narrow the bandgap. The article studied the influence of heat treatment time and visible light wavelength on sensing properties. The results show that under the conditions of room temperature and blue light irradiation, the coating heat-treated in a reduced atmosphere for 1 h showed the best gas-sensing properties to 1 ppm NO2 with a response of 7.0. The outstanding selectivity of ZnO1-α coating has been displayed.

Preparation and characterization of Sr0.5Ba0.5Nb2O6 glass-ceramic on piezoelectric properties

We studied the influence of heat treatment time on the optical, thermal, electrical, and mechanical properties of strontium barium niobate (Sr1−xBaxNb2O6; hereafter SBN) piezoelectric glass-ceramics with tungsten bronze-type structure, which have good piezoelectric properties and are important lead-free piezoelectric materials. We found that the best heat treatment time is 4 h. The properties of the prepared materials are better than that of SBN ceramics and the glass-ceramic growth is faster than the SBN crystal when the heat treatment time of the SBN piezoelectric glass-ceramic is controlled, reducing the preparation costs greatly.

The Influence of Heat Treatment Time and Temperature on the Physical Properties of Assab-Corax Steel

X-ray diffraction experiment was carried out on commercial Assab-Corax steel sample. The polished samples are then heated to various temperature for different holding time; 200 o C for 4 hours, 300 o C for 4 hours, 400 o C for 6-, 8-, 12- and 16 hours, 500 o C for 4 hours and 600 o C for 4 hours. The refinement of the diffraction intensity was carried out using the Im3m model, and the results show that the Carbon atoms are distributed among the base position in the body centered cubic unit cell at the eight-fold octahedral interstitial sites. Using the refined structural parameters, thermo-physical properties such as Debye temperature and coefficient of thermal expansion are calculated. From the results of the analysis it could be concluded that Debye temperature in Assab-Corrax steels tend to decrease with increasing heat-treatment time but tend to increase with heat treatment temperature. The coefficients of linear expansion also tend to decrease with increasing heat-treatment time and tend to increase with heat treatment temperature. Although the patterns are different, for example when the Debye temperature reaches its peak value for heat treatment time of 8 hours, the coefficient of linear expansion would reach its low point at this time. Therefore, the general finding is that both treatment-temperature and – time are influential to the physical properties of Assab-Corrax steels and x-ray diffraction methods could be utilized in elucidating these important findings.

Influence of Heat Treatment Time and Temperature on the Microstructure and Corrosion Resistance of Cast Superaustenitic Stainless Steels

Abstract The influence of heat treatment time and temperature on the microstructure and corrosion resistance of cast stainless steel alloys CN3MN (UNS J94651) and CK3MCuN (UNS J93254) were investig...

Effect of heat treatment on transformation temperatures and bending properties of nickel–titanium endodontic instruments

To investigate the effect of heat treatment on the bending properties of nickel-titanium endodontic instruments in relation to their transformation behaviour. Nickel-titanium super-elastic alloy wire (1.00 mm Ø) was processed into a conical shape with a 0.30 mm diameter tip and 0.06 taper. The heat treatment temperature was set at 440 or 500 degrees C for a period of 10 or 30 min. Nonheat-treated specimens were used as controls. The phase transformation behaviour was examined using differential scanning calorimetry. A cantilever-bending test was used to evaluate the bending properties of the specimens. Data were analyzed by ANOVA and the Tukey-Kramer test (P = 0.05). The transformation temperature was higher for each heat treatment condition compared with the control. Two clear thermal peaks were observed for the heat treatment at 440 degrees C. The specimen heated at 440 degrees C for 30 min exhibited the highest temperatures for M(s) and A(f), with subsequently lower temperatures observed for specimens heated at 440 degrees C for 10 min, 500 degrees C for 30 min, 500 degrees C for 10 min, and control specimens. The sample heated at 440 degrees C for 30 min had the lowest bending load values (P < 0.05), both in the elastic range (0.5 mm deflection) and in the super-elastic range (2.0 mm deflection). The influence of heat treatment time was less than that of heat treatment temperature. Change in the transformation behaviour by heat treatment may be effective in increasing the flexibility of nickel-titanium endodontic instruments.

The influence of lithia content on the properties of fluorphlogopite glass-ceramics. II. Microstructure hardness and machinability

The influence of heat treatment time and temperature on microstructure, hardness and theoretical machinability of glass-ceramics based on 8SiO 2 3Al 2O 3 (3− S)MgO 3MgF 2 (1− Z)BaOZK 2OSLi 2O where lithia was substituted for magnesia and baria for potassia were investigated. Lithia and potassia were found to promote the crystal coarsening of the fluorphlogopite phase and the development of a house of cards microstructure. Hardness was found to decrease slightly on formation of the fluorphlogopite phase, but to decrease markedly on development of the house of cards microstructure. The formation of the house of cards microstructure was promoted by heat treatments close to the observed melting endotherms and was associated with good machinability. Incorporation of lithia was found to suppress the formation of cordierite in the bulk.