Optimum Solution Heat Treatment Research Articles

Influence of Heat Treatment on Microstructure and Mechanical Properties of AZ61 Magnesium Alloy Prepared by Selective Laser Melting (SLM).

From previous studies, it is known that the dissolution of β-Mg17Al12 at high temperature and the increase of densities at high pressure after hot isostatic pressing (HIP) are the two main reasons for significant improvement in the ductility of AZ61 magnesium alloy prepared by SLM. However, the mechanism of dissolution of β-Mg17Al12 in SLMed AZ61 magnesium alloy at high temperature is not clear. To illustrate the mechanism of the effect of β-Mg17Al12 dissolution on the ductility of SLMed AZ61 Mg alloy, the effect of solid solution heat treatment (T4) on the microstructure and mechanical properties of SLMed AZ61 was investigated and the kinetic model of β-Mg17Al12 dissolution of SLMed AZ61 magnesium alloy was established. According to the results, there is no significant change in the dissolution of the β-Mg17Al12 with an increase of temperature and time when the T4 temperature is lower than 410 °C. At the optimum solution heat treatment temperature of 410 °C, the dissolution rate is accelerated and the β-Mg17Al12 is completely dissolved after 2 h. In addition, the dissolution rate of β-Mg17Al12 decreases with the increase of dissolution time. The strength of SLMed AZ61 magnesium alloy decreases and the ductility increases as the T4 temperature increases. The strength of the specimens is reduced by grain coarsening (29.2 ± 3.7 μm), but the elongation is increased by 90% compared to SLMed AZ61, due to the effect of β-Mg17Al12 dissolution.

Effects of heat treatment on microstructure and high-temperature tensile properties of nickel-based single-crystal superalloys

The effects of different heat treatments on the microstructure and the high-temperature tensile properties of a Ni-based single-crystal superalloy were investigated. Experimental results indicated that the Ni-based single-crystal superalloy had severe solidification segregation in the as-cast state, and a large amount of eutectic existed in the inter-dendritic region. To determine the heat-treatment window, the method of homogenization pretreatment was employed. The optimum solution heat treatment was 1280 °C/2 h + 1315 °C/2 h + 1320 °C/2 h + 1325 °C/6 h, AC, and the optimum aging treatment was 1120 °C/4 h, AC + 900 °C/24 h, AC. The shape, size, and distribution of γ′ precipitate had significant effects on the high-temperature tensile properties of the single-crystal alloy. After the optimum heat treatment, the high-temperature tensile strength of the Ni-based single-crystal superalloy was 720.8 MPa, and the elongation was 18.2% at 1000 °C.

The effect of solution treatment on aging behavior and mechanical properties of AA2024-TiB2 composite synthesized by semi-solid casting

AA2024 reinforced with varying amounts of titanium boride (TiB2) was developed using stir rheocasting to study the effect of solution heat treatment on aging behavior and mechanical properties. The developed specimens were subjected to solution heat treatment at 490 °C for 1, 2.5, and 5 h, followed by artificial aging at 190 °C for an aging duration of 1–12 h. The metallurgical characterization was done by x-ray diffraction, optical microscopy, and field emission scanning electron microscope and mechanical characterization by Vickers hardness tester and universal testing machine. Microstructural observation showed the formation of globular grains and fairly uniform particle distribution. Up on peak aging, the AA2024/2 wt% TiB2 composite has shown better improvement in yield strength (YS = 230 MPa), tensile strength (UTS = 342 MPa), and Vickers hardness (VH = 147) amongst other developed specimens. The improvement in mechanical properties of AA2024/2 wt% TiB2 composite up on peak aging was nearly 83%, 77%, and 20%, respectively, over their as-cast states. However, the percent elongation has decreased by 51% for the AA2024/2 wt% TiB2 composite against its as-cast state. The optimum solution heat treatment time was found to be 2.5 h that led to the fastest aging kinetics and peak hardness. Due to incomplete dissolution of precipitates at a solution treating time less than 2.5 h, the hardness decreased, and the aging kinetics decelerated. The aging kinetics further accelerated with increasing solution heat treating time beyond 2.5 h, but the hardness decreased due to grain growth of the matrix.

The effects of heat treatment on microstructure and mechanical properties of rheocasting ADC12 aluminum alloy

The effects of heat treatment on microstructure and mechanical properties of rheocasting ADC12 aluminium alloy produced by gas induced semi-solid (GISS) technique were studied. The solution heat treatment performed at the temperature of 520°C under various solution treatment times for 2, 4, 6, 8, 10, and 12 h and followed by water quenching at room temperature. The results show that the optimum solution heat treatment condition for the non-dendritic structure of ADC12 aluminium alloy was 520°C for 8 h. The age hardening was also carried out at 170°C for different aging times of 6, 8, and 10 h, respectively. It was found that the artificial aging at 170°C for 6 h was sufficient to achieve the highest hardness of 73.2 HRB. This was due to the appropriate refinement of acicular eutectic structure.

Optimizing the tensile properties of Al–Si–Cu–Mg 319-type alloys: Role of solution heat treatment

The work presented in this study was carried out on Al–Si–Cu–Mg 319-type alloys to investigate the role of solution heat treatment on the dissolution of copper-containing phases (CuAl2 and Al5Mg8Cu2Si6) in 319-type alloys containing different Mg levels, to determine the optimum solution heat treatment with respect to the occurrence of incipient melting, in relation to the alloy properties. Two series of alloys were investigated: a series of experimental Al–7wt% Si–3.5wt% Cu alloys containing 0, 0.3, and 0.6wt% Mg levels. The second series was based on industrial B319 alloy. The present results show that optimum combination of Mg and Sr in this study is 0.3wt% Mg with 150ppm Sr, viz. for the Y4S alloy. The corresponding tensile properties in the as-cast condition are 260MPa (YS), 326MPa (UTS), and 1.50% (%El), compared to 145MPa (YS), 232MPa (UTS), and 2.4% (%El) for the base alloy with no Mg. At 520°C solution temperature, incipient melting of Al5Mg8Cu2Si6 phase and undissolved block-like Al2Cu takes place. At the same time, the Si particles become rounder. Therefore, the tensile properties of Mg-containing alloys are controlled by the combined effects of dissolution of Al2Cu, incipient melting of Al5Mg8Cu2Si6 phase and Al2Cu phase, as well as the Si particle characteristics.

Al-Zn-Mg 반용융 압출재의 용체화처리

In the present study, the microstructure and solution treatment response of Al-Zn-Mg alloys bars by thixo-extrusion was investigated. The alloy bars were solution treated at 400, 430, 460 and <TEX>$490^{\circ}C$</TEX> for various times. In order to examine the microstructures and phase analysis of the samples after solution treatment, it was performed by optical and scanning electron microscopy. And, Vickers hardness and electrical conductivity was measured on the solution treated samples for each condition to investigate the solution treatment response of extruded bars during solution treatment. The results show that the optimum solution heat treatment conditions of thixo-extruded Al-Zn-Mg alloy for minimization of the grain growth and degradation promotion of the second phase is a temperature of <TEX>$460^{\circ}C$</TEX> and holding time of 0.5 to 2 h.

Influence of Solution Heat Treatment Temperature and Time on the Microstructure and Mechanical Properties of Gas Induced Semi-Solid (GISS) 6061 Aluminum Alloy

The influence of solution heat treatment (SHT) temperature and time on the microstructure and mechanical properties of semi-solid 6061 aluminum alloy has been investigated in this study. Microstructure of the as-cast 6061 aluminum alloy mainly consisted of globular α-Al matrix and eutectic phase (α-Al + Mg2Si) at the grain boundary (GB). Iron rich intermetallic phase was also observed at the grain boundary. Eutectic phase started to dissolve after solution heat treatment. The dissolution of eutectic phase increased with increasing solution treatment time, however, the amount of remaining eutectic phase was found to be slightly changed after solution treating longer than 1 h at 550 °C and 2 h at 530 °C. Hardness and tensile results of specimens after artificial aging were utilized to compare and select the optimum solution heat treatment condition cooperating with the microstructural observation. The optimum solution heat treatment condition of the alloy in this study was at 530 °C for 2 h.

T6 heat treatment of rheocasting 7075 Al alloy

Abstract Effects of solution heat treatment and age hardening on the microstructures and mechanical properties of rheocasting 7075 Al alloy produced by a novel technique, Gas Induced Semi-Solid (GISS) technique, were studied. This work reveals that the optimum solution heat treatment condition for the non-dendritic structured 7075 aluminium alloy was 450 °C for 4 h. Age hardening was performed at temperatures of 120 °C, 145 °C, 165 °C, and 185 °C under various time durations. The peak aging condition was the artificial aging at 120 °C for 72 h, at which a highest tensile strength of 486 MPa with 2% elongation was recorded. This higher strength was caused by higher number density and finer precipitate size of η / phase than other aging temperatures. The main hardening phase was identified to be the η / phase while early nucleation of η phase in the higher aging temperature specimens resulted in lower strengths of the alloy. The activation energy for the precipitate hardening process of the alloy derived in this research was 95,827 J/mol.

Influence of solution heat treatment on microstructure and stress rupture properties of a Ni 3Al base single crystal superalloy IC6SX

The effect of solution heat treatment at different temperatures on the microstructure and stress rupture properties of a Ni 3Al base single crystal superalloy IC6SX has been investigated in this paper. The experimental results show that the as-cast alloy exhibited a typical dendritic structure with three phases of γ′, γ and NiMo. After solution heat treated at 1240 °C, the NiMo phase dissolved entirely. With the temperature increasing, the γ′ phase in interdendritic region dissolved earlier than that in dendritic region. When solution heat treatment temperature reached to 1280 °C, all of the γ′ solutioned and a uniform microstructure was observed. Furthermore, increasing the temperature up to 1340 °C, a small amount of incipient melting occurred in the alloy. The stress rupture life of IC6SX at 1100 °C/130 MPa increased with the rising of temperature and reached to the top value under the solution heat treatment temperature of 1280 °C. The optimum solution heat treatment considered to be 1280 °C/10 h followed by flowing air cooling.

Microstructure characteristics in non-modified and Sr modified Al–Si–Cu–Mg 319 type alloys

This study was carried out on 319 alloys containing low and high levels of Mg, in the non-modified and Sr modified conditions (150 ppm Sr addition). Single step, two step and triple step heat treatments were applied to identify the optimum solution heat treatment to minimise incipient melting of the copper phases Al2Cu and Al5Mg8Cu2Si6 in these alloys in relation to the alloy properties. In Mg free alloys, no incipient melting of Al2 Cu was observed even in samples heat treated at 520°C. Addition of Sr leads to modification of Si particles but also to an increase in area per cent porosity and pore length, especially when the solution temperature reaches 520°C. Addition of Mg results in a decrease in the Si particle aspect ratio but an increase in particle size. Magnesium was also found to increase the possibility of incipient melting resulting from the formation of the insoluble Al5Mg8Cu2Si6 phase. To some degree, Sr decreases the effect that Mg has in increasing the area per cent porosity and pore length, while Mg impairs the effects that Sr has on modifying Si particles, even though the lowest Al–Si eutectic temperature is obtained for the 319 alloy containing both Mg and Sr.

Effect of heat treatment on microstructure and stress rupture life of DD32 single crystal Ni-base superalloy

The effect of heat treatment on microstructure and stress rupture life of DD32 single crystal Ni-base superalloy was investigated in this paper. Experimental results show that the more regular the cubic shape of γ′ precipitate, the more homogeneous the size of γ′ precipitate, the longer the creep rupture life after heat treatment. The solution temperature has more significant role on the microstructure than the hold time. The optimum solution heat treatment is 1280 °C/4 h, ac + 1290 °C/4 h, ac and the optimum high temperature ageing treatment is 1150 °C/4 h, ac. MC-type carbide in DD32 alloy is very stable during heat treatment.