A low transformation temperature (LTT) welding consumable has been developed to prevent cold cracking in high strength steel welded joints without preheating. In the LTT welded joint, the residual tensile stress is reduced by martensitic expansion of weld metal formed by the LTT consumable. In the weld cracking tests, cold cracking in the LTT weld metal is successfully prevented under high restraint conditions, but cold cracking occurs at very low joint restraint strength in case the weld metal is fully martensitic. Chemical compositions of the consumable are designed to retain austenite in martensite in the newly developed weld metal to absorb the diffusible hydrogen into the austenite to prevent cold cracking. In the newly developed LTT weld metal, cold cracking is almost fully suppressed without preheating under every joint restraint condition.

Samarium ions (Sm2+) incorporated into aluminosilicate glasses by a sol‐gel process showed persistent spectral hole burning at room temperature. Gels of the system Na2O‐Al2O3SiO2 synthesized by the hydrolysis of Si(OC2H5)4, Al(OC4H9)3, CH3 COONa, and SmCl3·6H2O were heated in air at 500°C, then reacted with H2 gas to form Sm2+ ions. Whereas Al3+ ions effectively dispersed the Sm3+ ions in the glass structure, Na+ ions were not effective. The Al2O3‐SiO2 glasses proved appropriate for reacting the Sm3+ ions with H2 gas and exhibited the intense photoluminescence of Sm2+ ions. The reaction of Sm3+ ions with H2 in the Al2O2‐SiO2 glasses was determined by first‐order kinetics, and the activation energy equaled 95 kJ/mol. At 800°C, the maximum photoluminescence of the Sm2+ ions was achieved within 20 min.

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The diffusion behavior of a carbon-acceptor impurity in a p+-n+ GaAs tunnel junction with a heavily carbon doped p+-layer was investigated in detail. The diffusion coefficients of carbon were deduced from the degradation rates of the peak current density of the GaAs tunnel diodes. The current-induced diffusion coefficient of carbon under forward bias operations at 2 kA/cm2 was given by D C,current\sevsize-induced=D 0exp (-E a/k T), where D 0=1.5×10-13 cm2/ s and E a=0.47±0.01 eV. In addition, the thermal diffusion coefficient was given by D C,thermal=D 0exp (-E a/k T), where D 0=1.1×10-9 cm2/ s and the activation energy E a=1.47±0.01 eV.

In order to improve fatigue strength in welded joints, low transformation-temperature welding wire has been developed in which residual tensile stress can be reduced. In application of the low transformation-temperature welding wire, the prevention of cold cracking without preheating in high strength steel welded joints is expected and examined from the control of residual tensile stress. However, it is expected that residual stress distribution in welded joint can be suggested by numerical analysis, because the residual stress cannot be measured simply and non-distractively. In this report, martensite transformation behavior such as Ms point, transformation expansion and so on is measured firstly by Formaster test. And temperature dependence of several mechanical properties was measured in full-austenite and full martensite microstructures, and temperature dependence of mechanical properties was estimated in dual phase microstructure of austenite and martensite. By these data, numerical analysis was carried out and martensite transformation behavior was compared with measured and calculated results in side rigid model test. From the comparison, it was suggested that transformation superplasticity had to be considered in numerical analysis. Next, the increase of Ms point due to transformation induced plasticity was guessed from the comparison with measured data by laser speckle measurement and calculated data under transformation superplasticity consideration. From the all results, it was found that the measured transformation behavior and residual stress had the good agreement with the calculated results under transformation superplasticity and transformation induced plasticity considerations.