Secondary austenite and chromium nitride precipitation in simulated heat affected zones of duplex stainless steels

Abstract

Primary and secondary intragranular austenite precipitation and its relationship with chromium nitride (Cr₂N) were studied in a simulated multipass heat affected zone (HAZ) of five duplex stainless steel alloys (UNS S32304, S32205, S32550, S32750, and S32760). The Gleeble thermal-mechanical simulator was used to perform short duration and high cooling rate ferritisation and reheating heat treatments. TEM and FEG-SEM analysis, coupled with a specially developed electrolytic etching technique, revealed the cooperative growth of secondary austenite and Cr₂N precipitation along the ferrite/austenite (α/γ) interfaces. Additionally, the observed close coexistence of intragranular nitride (Cr₂N) and intragranular secondary austenite suggests the heterogeneous nucleation of secondary austenite from the nitrides as supported by previously reported low energy nitride/austenite (Cr₂N/γ) interfaces for the observed orientation relationship between both phases. Based on these observations, a new mechanism is proposed for intragranular secondary austenite nucleation related to the intragranular nitride precipitates.     

Tailored waste based glasses as secondary raw materials for porcelain stoneware

Abstract

The high temperature processing of porcelain stoneware products is attractive for the possibility to incorporate several inorganic wastes. However, even if recycling is an environmental benefit, it can be disadvantageous for the overall properties of the ceramic product, if wastes are not selected in terms of their chemical and physical characteristics. In the present work several kind of industrial and urban wastes, such as mining residues, lime, glass from dismantled cathode ray tubes and soda lime glass were used, after their vitrification. These newly formed glasses were used as partial substitution for natural feldspar sands (the glass content being from 5 to 7 wt-% of the total mix). Owing to the specific ('tailored') chemical formulation of the newly formed glasses, the modified products exhibited higher crystallisation, with a more homogeneous microstructure, leading to significant improvements in reliability and indentation fracture toughness.     

Development of mechanical properties during secondary aging in aluminium alloys

Abstract

Earlier work has shown that, if the artificial aging of aluminium alloys is interrupted by a dwell period at lower temperature, higher values of tensile properties and fracture toughness may be achieved than are possible with single stage T6 tempers. A second interrupted aging cycle has now been developed that involves underaging at the elevated temperature, quenching, and then allowing secondary precipitation to occur at, or just above, room temperature. Designated a T6I4 (I=interrupted) temper by the authors, this simpler aging cycle may reduce heat treatment costs. Tests on some 30 cast and wrought alloys have resulted in tensile properties close to those for a T6 temper, with higher values of fracture toughness being recorded for some cases. Such an aging treatment can be incorporated into a paint bake cycle to simplify the heat treatment of coated automotive components.     

Adhesion strength and mechanism of poly(imide-siloxane) to Alloy 42 leadframe

Poly(imide-siloxane) containing α,ω-(aminophenoxypropyl)poly(dimethylsiloxane) and α,ω-(aminophenoxypropyl)poly(dimethylsiloxane-co-diphenylsiloxane) were synthesized. The adhesion strength of poly(imide-siloxane)/Alloy 42 leadframe (Fe-Ni alloy, 58% Fe and 42% Ni) joints was studied as a function of the molding temperature, time, pressure, and chemical structure of siloxane diamine (SDA). The thermo-oxidative decomposition of polydimethylsiloxane (PDMS) in poly(imide-siloxane) was examined by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Silanol groups were formed from the thermal decomposition of PDMS above 300°C. The adhesion mechanism of poly(imide-siloxane) with metal oxide was identified as the formation of covalent bonds between the silanol group of thermo-oxidatively decomposed PDMS and hydroxy groups of the metal oxide by time-of-flight secondary ion mass spectroscopy (TOF-SIMS).     

Jieshou to Build A Megaton Secondary Metals Market

【正】Recently,Jieshou Xicheng Recycling Economic Zone has started to prepare to establish the "East China Metals Distribution & Trading Market" by means of attrac...     

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Abstract

Deoxidation, desulphurisation and inclusion modification are some of the essential features in secondary steel refining through injection of calcium alloy in the form of a cored wire. It is imperative that the filling material must be consumed by the melt to the maximum extent in order to make this cored wire alloy addition cost effective and efficient. In this connection study of calcium recovery is an important issue, which may provide guidelines to select the optimum operating parameters from a fundamental basis. The present study is based on plant data from Tata Steel, Jamshedpur, India. The results demonstrate that maximum calcium recovery is achievable at an optimum speed of the cored wire. Dimensional analysis was carried out to analyse the plant data and the calcium recovery was found to correlate well with physically sound dimensionless numbers such as Biot number, the dimensionless bath temperature and the relative rate of silicon to sulphur transfer from/to the added calcium silicide in the melt. A correlation has also been obtained between the calcium recovery and various dimensionless parameters. The efficacy of calcium addition is also assessed through characterisation of inclusions by scanning electron microscopy and energy dispersive X-ray spectroscopy.     

30—THE INFLUENCE OF ORIGIN ON THE STRESS–STRAIN RELATIONS OF WOOL FIBRES

Stress–Strain data for wool fibres of different origin are presented, the tests having been made under different moisture conditions. Small differences exist between wool fibres from primary and secondary follicles from the same animal, the secondary being easier to stretch both initially and finally under wet conditions. However, the relative yield slope is markedly higher for secondary than for primary fibres. Differences exist between and within breeds in the initial modulus, the stress at 15% extension, and the slopes of the curves in the yield and post-yield regions.     

The Effect of Plate Making Conditions on the Tone Rendering Obtained Using Non-Dichromate Sensitized Lithographic Plates

Experiments designed to determine the effect of some of the variables encountered in plate making on the tone reproduction obtained from three different types of non-dichromate sensitized lithographic plates are described. Two of the plates studied were pre-sensitized. Of these one was negative and one was positive working. The other was a plate of the “wipe-on” type.     

Ultrasonic spot weld testing with automatic classification

Abstract

Spot welds can be tested non-destructively using ultrasound. By interpreting the signals received when testing, the quality of the weld may be determined. The method has not been widely accepted in the past, possibly owing to difficulties in manually quantifying the information contained in the signals. An automatic system to interpret the signals and classify welds has been developed in an attempt to aid human operation and as a step towards automatic, non-destructive spot weld testing. Details of a trial used to assess the performance of the system are given. By comparing the results with manual testing using ultrasound, the potential of automating signal interpretation is assessed. The results also indicate that the success of the ultrasonic technique, manual or automatic, is limited.