The time-resolved optical emission spectroscopy of Ti-Al alloy plasma produced by the Nd:YAG high-power laser pulses with wavelength of 1064nm was investigated both in air and vacuum conditions. The comparative studies gave detailed insights that the plasmas produced in air were much hotter and denser. The quantitative descriptions indeed suggested that a cascade avalanche process would be happen followed by air plasma firstly, before the laser impacting the target surface. On the other hand, the laser energy may be considerably attenuated via hotter and denser plasma, the amount of laser energy on the target surface remarkably decreased in air condition. In addition, at high-power laser irradiance levels, there was an auto regulatory area near the target surface and the plasma parameters tend to be saturated

The ultra-high strength quenched 22MnB5 steel is researched in this paper, the intermediate frequency inverter & electric servo welding gun system is used to weld the sheets, experiments included of tensile-shear with synchronous electrical testing, microstructure of the material and fractures analysis and the Vickers-Hardness testing. The results point out that the maximum hardness is located at weld nugget, and the minimum hardness is appeared in heat affected zone (HAZ). Fracture is formed under the combined effects of shear stress and normal stress, the shear stress contributes to interfacial fracture, and leads to rupture. Non-uniformity of the microstructure caused by spot welding, changed the property of the material in nugget, stress-strain relationship of this area is nonlinear. The results also show that the conventional weld size guidance of 4√t is not sufficient to produce nugget pullout failure mode for 22MnB5 UHSS spot welds.