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Evolution of microstructure and residual stress under various vibration modes in 304 stainless steel welds.

Hsieh CC, Wang PS, Wang JS, Wu W - ScientificWorldJournal (2014)

Bottom Line: The experimental results indicate that the temperature gradient can be increased, accelerating nucleation and causing grain refinement during this process.A residual stress can obviously be increased, producing an excellent effect on stress relief at a resonant frequency.The stress relief effect with an eccentric circulating vibrator was better than that obtained using a magnetic telescopic vibrator.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering, National Chung Hsing University, 250 Kuo-Kuang Road, Taichung 402, Taiwan.

ABSTRACT
Simultaneous vibration welding of 304 stainless steel was carried out with an eccentric circulating vibrator and a magnetic telescopic vibrator at subresonant (362 Hz and 59.3 Hz) and resonant (376 Hz and 60.9 Hz) frequencies. The experimental results indicate that the temperature gradient can be increased, accelerating nucleation and causing grain refinement during this process. During simultaneous vibration welding primary δ -ferrite can be refined and the morphologies of retained δ-ferrite become discontinuous so that δ-ferrite contents decrease. The smallest content of δ-ferrite (5.5%) occurred using the eccentric circulating vibrator. The diffraction intensities decreased and the FWHM widened with both vibration and no vibration. A residual stress can obviously be increased, producing an excellent effect on stress relief at a resonant frequency. The stress relief effect with an eccentric circulating vibrator was better than that obtained using a magnetic telescopic vibrator.

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The microstructures in the center of the welds with various vibration frequencies: (a) 0 Hz, (b) TX-VSR 362 Hz, (c) TX-VSR 375 Hz, (d) Meta-Lax 59.3 Hz, and (e) Meta-Lax 60.9 Hz.
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fig8: The microstructures in the center of the welds with various vibration frequencies: (a) 0 Hz, (b) TX-VSR 362 Hz, (c) TX-VSR 375 Hz, (d) Meta-Lax 59.3 Hz, and (e) Meta-Lax 60.9 Hz.

Mentions: Figures 8(a)–8(e) show the weld microstructures of 304 stainless steel with and without vibration. As shown in Figure 8(a), fine dendrites grew at the top of the welds without vibration and dispersed columnar grains were observed. Dendrites were found in the bottom of the welds for the subresonant and resonant frequencies produced by the magnetic telescopic vibrator, as shown in Figures 8(b)-8(c). Concerning solidification in the bottom of welds, vibration welding made it difficult to retard dendritic growth because of a higher degree of supercooling. The center of the welds indicated many equiaxed grains created at a subresonant frequency and, in addition, exhibited many dendritic grains at a resonant frequency. Figures 8(d)-8(e) show the weld microstructures created at subresonant and resonant frequencies using an eccentric circulating vibrator; similar grain refinement was displayed at a resonant frequency. However, perturbation motion can occur from the molten pool during vibration and the dendrites can be broken at the same time. Nucleation sites will be increased when broken dendrites are formed. On the other hand, the distribution of temperature is uniform during vibration welding, meaning that the temperature difference is small [12]; therefore, the effect of vibration should be the temperature gradient (G). Wei [4] pointed out that the vibration can accelerate the flow of liquid metal and redistribute the temperature of the weld pool. Hence, the temperature gradient can be decreased during solidification, and then the equiaxed grains are formed at the same time.


Evolution of microstructure and residual stress under various vibration modes in 304 stainless steel welds.

Hsieh CC, Wang PS, Wang JS, Wu W - ScientificWorldJournal (2014)

The microstructures in the center of the welds with various vibration frequencies: (a) 0 Hz, (b) TX-VSR 362 Hz, (c) TX-VSR 375 Hz, (d) Meta-Lax 59.3 Hz, and (e) Meta-Lax 60.9 Hz.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3926365&req=5

fig8: The microstructures in the center of the welds with various vibration frequencies: (a) 0 Hz, (b) TX-VSR 362 Hz, (c) TX-VSR 375 Hz, (d) Meta-Lax 59.3 Hz, and (e) Meta-Lax 60.9 Hz.
Mentions: Figures 8(a)–8(e) show the weld microstructures of 304 stainless steel with and without vibration. As shown in Figure 8(a), fine dendrites grew at the top of the welds without vibration and dispersed columnar grains were observed. Dendrites were found in the bottom of the welds for the subresonant and resonant frequencies produced by the magnetic telescopic vibrator, as shown in Figures 8(b)-8(c). Concerning solidification in the bottom of welds, vibration welding made it difficult to retard dendritic growth because of a higher degree of supercooling. The center of the welds indicated many equiaxed grains created at a subresonant frequency and, in addition, exhibited many dendritic grains at a resonant frequency. Figures 8(d)-8(e) show the weld microstructures created at subresonant and resonant frequencies using an eccentric circulating vibrator; similar grain refinement was displayed at a resonant frequency. However, perturbation motion can occur from the molten pool during vibration and the dendrites can be broken at the same time. Nucleation sites will be increased when broken dendrites are formed. On the other hand, the distribution of temperature is uniform during vibration welding, meaning that the temperature difference is small [12]; therefore, the effect of vibration should be the temperature gradient (G). Wei [4] pointed out that the vibration can accelerate the flow of liquid metal and redistribute the temperature of the weld pool. Hence, the temperature gradient can be decreased during solidification, and then the equiaxed grains are formed at the same time.

Bottom Line: The experimental results indicate that the temperature gradient can be increased, accelerating nucleation and causing grain refinement during this process.A residual stress can obviously be increased, producing an excellent effect on stress relief at a resonant frequency.The stress relief effect with an eccentric circulating vibrator was better than that obtained using a magnetic telescopic vibrator.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering, National Chung Hsing University, 250 Kuo-Kuang Road, Taichung 402, Taiwan.

ABSTRACT
Simultaneous vibration welding of 304 stainless steel was carried out with an eccentric circulating vibrator and a magnetic telescopic vibrator at subresonant (362 Hz and 59.3 Hz) and resonant (376 Hz and 60.9 Hz) frequencies. The experimental results indicate that the temperature gradient can be increased, accelerating nucleation and causing grain refinement during this process. During simultaneous vibration welding primary δ -ferrite can be refined and the morphologies of retained δ-ferrite become discontinuous so that δ-ferrite contents decrease. The smallest content of δ-ferrite (5.5%) occurred using the eccentric circulating vibrator. The diffraction intensities decreased and the FWHM widened with both vibration and no vibration. A residual stress can obviously be increased, producing an excellent effect on stress relief at a resonant frequency. The stress relief effect with an eccentric circulating vibrator was better than that obtained using a magnetic telescopic vibrator.

Show MeSH