Phase transformations in an AISI 410S stainless steel observed in directional and laser-induced cooling regimes

The applications of the chromium ferritic stainless steel AISI 410S have been considerably increased in the last years in many technical fields as chemical industries and oil or gas transportation. However, the phase transformation temperatures are, currently, unknown for this alloy. The aim of this work is to determine the alpha to gamma transformation temperatures of the AISI 410S alloy in different cooling conditions and to analyze them using continuous cooling theory. In order to achieve different cooling rates and thermal conditions, two complementary techniques were used: Bridgman furnace crystal growth and laser remelting technique. The measured solidification temperature was around 1730 and 1750 K. Plate-like and dendritic austenite precipitates were obtained in solid-state phase using growth rates between 5 and 10 µm/s in directional growth experiments. Only plate-like austenite phase was observed in the experiments using growth rates above 100 µm/s. The appearance of dendrites, with the consequent segregation of the elements, can be previously determined by the microstructure modeling currently proposed. Massive austenite can be produced from 0.3 to 10 mm/s rates at temperatures between 1100-1300 K. The structure might be less sensitive to corrosion because this phase is produced without microsegregation.Commission of Technology and Innovation (Switzerland)Swiss Steel Co.Instituto de Estudos Avançados Centro Técnico AeroespacialUniversidade Federal de São Paulo (UNIFESP) Instituto de Ciências Ambientais, Químicas e Farmacêuticas Departamento de Ciências Exatas e da TerraUNIFESP, Instituto de Ciências Ambientais, Químicas e Farmacêuticas Depto. de Ciências Exatas e da TerraSciEL

PARÂMETROS DO VALOR NUTRITIVO DE NOVE VARIEDADES DE CANA-DE-AÇÚCAR CULTIVADAS SOB IRRIGAÇÃO

Avaliaram-se alguns parâmetros do valor nutritivo de nove variedades de cana-de-açúcar cultivadas sob irrigação, a saber: RB 72454, RB 835486, RB 845257, SP 813250, RB 855536, SP 835073, SP 801842, SP 801816 e SP 791011. O delineamento experimental foi o inteiramente casualizado com três repetições. Os teores de sacarose (POL) e a relação FDN/POL diferiram (

Laser Beam Welding of CubeSat 1U Structure Parts Obtained by Powder Bed Fusion

This study contributes to a possible methodology for manufacturing CubeSats using additive manufacturing and laser beam welding. Titanium connectors were constructed by selective laser melting and electron beam melting and characterized from a topological point of view. The connectors can be joined to titanium tubes for the construction of CubeSats via laser spot welding. The fiber laser welds exhibited full penetration using pulses with 400 J of energy. The welds showed titanium acicular martensite grains with recesses and pores. The average hardness of the cast zone was 350 HV, which is close to the hardness of the connectors (400 HV) and more rigid than that of the tubes (100 HV). Spot welding has proven to be useful in resisting forces above 2000 N, which is sufficient for CubeSat frame space applications

Laser surface remelting and hardening of an automotive shaft sing a high-power fiber laser

An automotive shaft was surface-remelted and hardened using a 2 kW fiber laser and an adapted linear axis whose rotating axis produced helical tracks at 120 RPM. The process variable was the laser power, ranging from 300 to 1100 W, which produced two regions in the material: a martensitic region (MR) and a partially transformed region (PTR). The MR is formed after rapid solidification or austenitization followed by rapid cooling (10(7) K.s-1). The PTR is composed of martensite, unchanged pearlite and proeutectoid ferrite. The maximum case depth was about 0.3 mm. The microhardness inside the martensitic regions are at least double that of the base material, i.e. between 800 than 600 HV compared to 300 HV. Thermal simulations using a modified Rosenthal formalism help elucidate the phase transformation inside the material and show good agreement with experimental results. The experimental laser-steel absorptivities were measured; they ranged between 38 and 59% depending on the laser power and the amount of liquid at the surface

Investigation of Laser Treatment as a Method for Fatigue Crack Growth Retardation in Aluminum Alloy 2198-T851

Among the third-generation Al-Li alloys, AA2198 stands out for its lower density, formability and increased stiffness, being suitable for use in aircraft fuselage sheets and other inner structures in order to reduce weight and improve performance. An important topic related to damage tolerant structures is the development of techniques to retard fatigue crack propagation, such as the localized heating by a laser source. The aim of the present work was to find the most suitable parameters for the production of laser heating lines in 2198-T851 alloy sheets in order to reduce the fatigue crack growth rate in this material. Laboratory tests using C(T) specimens under two loading conditions (R = 0.1 and 0.5) provided a useful dataset on the laser heated material. The experimental results indicate a 200 W laser beam power at treatment speeds of 1 and 10 mm/s was sufficient to retard crack growth in the current setup. The more expressive results were obtained for 200 W laser power with a speed of 1 mm/s and cyclic loading with stress ratio R = 0.1

A Novel Proposal to Manipulate the Properties of Titanium Parts by Laser Surface Alloying

A novel proposal is presented to increase the fatigue strength of titanium parts by applying a less rigid coating, which is expected to lower the tensile stresses at the surface and delay the onset of fatigue cracking. Niobium was introduced into the surface layer by laser surface alloying and, depending on the process parameters, beta and alpha" phases were obtained, resulting in a reduction of approximately 30% in Young's modulus and a more than 100% increase in hardness. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.The authors would like to thank the Sao Paulo State Research Foundation (FAPESP, Brazil) for financial support and Professor Conrado R.M. Afonso of the Structure Characterization Laboratory (LCE, Brazil).Fogagnolo, JB.; Rodrigues, AV.; Lima, MSFD.; Amigó Borrás, V.; Caram, R. (2013). A Novel Proposal to Manipulate the Properties of Titanium Parts by Laser Surface Alloying. Scripta Materialia. 68(7):471-474. doi:10.1016/j.scriptamat.2012.11.016S47147468