The paper presents results of microstructure and mechanical properties investigation of laser beam welded high-strength steel. Material for test was non-alloyed steel with yield strength of 690 MPa after quenching and tempering in delivery condition. Research carried out on the butt-welded joints shows fine-grain martensitic-bainitic structure of base metal and in the weld. Investigations of mechanical properties revealed the softened zone in HAZ where the hardness decrease without microstructural changes was observed. Moreover, an influence of softened zone and HAZ width on impact strength was observed where the occurrence of lower hardness led to fracture path deviation phenomenon.

Recycling of raw materials and is crucial for the production of new products for the global economy. The aim here is, on the one hand, to reduce energy consumption, and, on the other hand, to obtain materials with similar functional properties. The study undertook research on the possibility of processing AlSi11 aluminum chips by compaction and co-extruding to obtain a product in the form of a flat bar with mechanical properties not lower than those of the cast materials. The performed tests and the developed technique allowed to obtain flat bars with more favorable mechanical properties (Yield Strength YS ≥ 155 MPa; Ultimate Tensile Strength UTS ≥ 212 MPa) than the castings (YS ≥ 70 MPa ≥ 150 MPa). The weldability evaluation tests revealed that the material is susceptible to porosity. The presence of pores, which reduces the cross-section (up to 60%), reduces the tensile strength (up to 20 MPa). The typical joint structure and plasticity is obtained, which indicate the possibility of tensile strength improvement.

This article presents the results of research on the development of the technology of laser beam butt welding of 17-4 PH stainless steel sheets and the technology of post-weld heat treatment (PWHT). The developed technology allows for favorable conditions to be obtained and for the appropriate microstructure and hardness to exist in the weld area. Moreover, it enables the fulfillment of a number of specific requirements beyond the possibilities of manual welding and other methods. The tests performed include the analysis of the microstructure with the use of light microscopy (LM) for the materials after welding and PWHT. The applied PWHT showed changes in the microstructure and mechanical properties. In all weld areas the martensitic microstructure was observed. The homogeneity of the microstructure in the area of the welded joint after PWTH was revealed. In the as-welded condition and after the PWHT with aging at 481 °C, the hardness was 440 HV5, but after aging at 621 °C, it decreased to 330–340 HV5.

This article presents a study on the influence of temperature and time of multi-variant heat treatment on the structure and properties of materials produced in direct metal laser sintering (DMLS) and casting technology. The materials were manufactured in the form of cuboidal elements with a cross-section of 1.5 mm × 15 mm and a length of 60 mm. The samples prepared in this way had a similar volume, but due to the production technology the metal crystallization took place at different rates and directions. In the cast, the direction of heat transfer was toward the mold, and the DMLS was directed locally layer by layer. The small thickness of the cast material allowed reaching conditions similar to the DMLS cooling process. Both DMLS and cast samples show similar mechanical properties (hardness) achieved after long ageing time, i.e., 16 h at 170 °C. The maximum hardness was observed for 8 h. In the DMLS samples, in contrast to cast samples, no lamellar precipitates of silicon were observed, which indicates their better resistance to cracking

The paper presents research results of the influence of heat input into high carbon rail steel during cutting processes on microstructure transformation and cracking. The massive block of steel prepared for rail rolling processes was cut and examined by nondestructive magnetic testing and destructive testing by microscopic examination and hardness measurements. The results show unfavorable microstructure changes where pearlite and transformed ledeburite were obtained. The effects of the presence of such microstructures are high hardness near to cutting surfaces (above 800 HV) and microcracks which grow into low hardness block cores during rolling and rail shaping.