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High-strength low-alloy steel 50 mm thick is well joined by metal-active gas double-sided doublepower arc welding, which does not require preheating, postheating, and back chipping. Mechanical properties of the weld seam and base metal were investigated. Results of the tensile test indicate that the strength of the weld seam is about 862.73 MPa and its average elongation is 20.74%. The hardness of the base metal and weld zone is 299 and 361 HV, respectively. The maximum hardness (395 HV) is observed in the heat-affected zone. The average toughness of the face and root sides of the weld center is 75 and 71 J, respectively.

SiC fibre with the transverse isotropic properties is very important to it reinforced metal matrix composites. In this paper, local texture of the CVD SiC fibre was investigated by means of X-ray diffraction (XRD) and precession electron diffraction (PED) on transmission electron microscopy (TEM). The result from XRD is in agreement with the result obtained from PED. And the result shown that at the first stage of deposition, the preferred direction of SiC grains is almost random and the distribution of grain size is scattered. At the second and third stages of deposition, there are two kinds of texture in SiC fibre, that is, (110),111. and (110),115.. Furthermore, the grain size at the second and third stages is about 200 nm and it is lower at the third stage than at the second stage because of the lower temperature at the third stage. The [110] preferred direction along axial direction for SiC fibre is beneficial to the axial tensile strength.

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