This study investigates the stress evolution and microstructural changes in TC4 titanium alloy through isothermal gradient solution quenching (900~1000°C solution treatment, water quenching at room temperature and 60°C), followed by annealing at 700~800°C and aging at 500~550°C.

This paper presents the results of a study on a new coating method for alloy steel. The coatings were synthesized on the surface of H21 die steel through a combination of thermal-chemical treatment (TCT) and electron beam processing (EBP). A paste containing boron and aluminum was applied to the test samples which were then heated to accelerate the diffusion process. After 2 h at 950 °C, the diffusion layers were found to be 120 μm thick, and after 2 h at 1050 °C, they were 580 μm thick. The subsequent EBP led to a complete transformation of the primary diffusion layer and an increase in thickness to 1.6 mm. XRD analysis showed significant differences in composition before and after EBP and the presence of tungsten and iron borides. It was also found that the distribution of microhardness and composition over the layer thickness had a more favorable profile after EBP.

Forging processes include various steps to attain favorable material properties such as heat treatment, rapid quench, cold work stress relieving, and artificial aging. These steps, however, also contribute to bulk residual stress. Excessive bulk residual stresses cause a wide of problems, including part distortion during machining and in use, reduced crack initiation life, increased crack growth rates, and an overall reduction in part life. This paper summarizes recent work aimed at measurement-based assessment of bulk residual stresses in cold-compressed aluminum die forgings. The results show that forging process induced residual stress is a repeatable phenomenon with RMS repeatability less than 5% of yield.

This paper will present the advantages and disadvantages of quenching media options like HPGQ (high pressure gas quenching), Oil and Press Quenching, Austempering (salt) for steel, ADI (austempered ductile iron) and aluminum to achieve certain targets relating to automotive component heat treating. Each heat treating/quenching process provides unique solutions for automobile designers and plant engineers. However, there likely is no single process or material that provides all of the answers that one would desire. Therefore, what process or combination of processes will satisfy the overall need? Detail will be discussed that outlines how OEM’s and heat treaters can and do take advantage of a particular hardening process.

Heat treatment is a common manufacturing process in automotive industry to produce high performance components such as cylinder heads and cylinder blocks. Although heat treatment incorporating a quenching process, either by high velocity air flow or water, can produce parts with durable mechanical properties, an unwanted effect of intense quenching processes is that they also induce thermal residual stress, which often is a leading cause for quality issues associated with high cycle fatigues. During product development cycle, it is not uncommon to switch between air and water quench media and change quench orientation in order to minimize residual stress. However, the choice of quench media and quench orientation is often determined by intuitive engineering judgement at best and trial-and-error iterative method at worst. With the advancement of CFD technologies, the temperature profile and history of quenching processes now can be accurately calculated. Since thermal residual stress is directly linked to non-uniform temperature distribution in the metal, spatial temperature gradient of each quenching process is evaluated to study and compare the performance of different quench media and configuration. The conclusion of this study can be used to establish engineering guidelines for future product development.

Recent destructive analysis of six ASTM A350 LF2 flanges has revealed vastly different low temperature (-50°F) Charpy impact toughness from 4 J (3 ft-lbs) to greater than 298 J (220 ft-lbs). These relatively low strength flanges, minimum 248 MPa (36 ksi) yield and 483-655 MPa (70-95 ksi) tensile strength, had nominally the same yield and UTS despite the difference in toughness. Detailed chemical and microstructural analysis was undertaken to elucidate the cause of the toughness range. The majority of the flanges had aluminum additions and a fine grain size with the toughness differences mostly explained by the cooling rate after normalizing with the still air cool showing the lowest toughness and the fastest air cooled sample the highest. For flanges of this strength level a quench and temper operation is not required to obtain good low temperature toughness but forced air cooling after normalizing is a minimum cooling rate to ensure good toughness and overall strength.