Papers by Keyword: Solid Solution Treatment

Abstract: This research is aimed to study effect of holding time and temperature in solution treatment and ageing on the hardness of the Aluminum A356 reinforced with silicon carbide particles. Alumimium matrix coposite was particulated with 15 microns-SiC with the content of 15 percent by weight. A356/SiC composites was prepared by the stirr casting. The stirrer was continuously stired at a speed of 300 rpm during acooling temperature to semi-solid state of 610 °C. During stirring the SiC powder was slowly added into the melt and continuously stirred for another 10 min. Then poured into the mold at the pouring temperature of 680°C. A356/SiC composites then subjected to a solid solution treatment with temperature of 540 °C for 1 hr. quenched with water and age hardening temperature of 120 and 135 °C for 3, 6, 12 and 18 hr. The result showed that, in as cast conditions, the composite with 15 microns silicon carbide, the 15 wt%SiC specimen exhibited the average hardness of 64.33 HB. After solution treated, the hardness of samples decreased. the specimen exhibited the average hardness of 53.83 HB. After ageing, the hardness of samples increased. the specimen ageing 120 °C 6 hr. exhibited the lowest average hardness of 51.45 HB while the specimen ageing 135 °C 18 hr. exhibited the highest average hardness of 73.54 HB.

Abstract: In this study, effect of die pressure and injection speed on hardness and microstructure in rheo-die casting of A356-SiC composite was investigated. The master A356-SiC composite was first produced by the mechanically stirred casting. SiC-15 micron particle was added 15 wt% in the molten A356. Master composites were then remelted at 610-615 °C. Then the slurry was transferred to a ladle and injected into the die. The Injection speeds were 3 and 4 m/s and die pressures were 11 and 12 MPa. Slurry was injected into a rod of 16×15.6×205 mm. Samples were then subjected to T6 treatment: solution treated at 540 °C for 1 h, water quenched then aged at 135 °C for 12 h. The result showed that hardness increased with increasing both speed and die pressure. At speed of 3 m/s and die pressure of 11 MPa which was an injection condition recommended for the molten A356, rheo-casted sample exhibited uneven filling at the end of the rod. When both speed and die pressure increased, samples were successfully and evenly filled the die cavities. Brinell hardness tests were performed in both as-rheo casted and T6 conditions. In as-rheo casted condition, the maximum hardness value of 82.16 HB obtained from a sample rheo-casted with speed of 4 m/s and die pressure of 12 MPa. A microstructure in cross section area of a rod revealed a uniform distribution of SiC particles in the A356 matrix. After T6, hardness value of composites increased approximately 15.6%.

Abstract: The microstructure evolution of the Mg-4.5Zn-0.75Er alloy containing quasicrystalline phase (I-phase) during heat treatment and hot compression was investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was found that the as-cast alloys mainly consisted of α-Mg matrix and I-phase. The I-phase with different morphologies could be found at both matrix and interdentritic boundaries. The I-phase almost dissolved into the matrix at 460 °C, meanwhile, some magnesium-rare earth phase (Mg-Er phase) was precipitated and the volume fraction increased with prolonging the solid solution time. The true stress-strain curve obtained from the hot compression test showed the flow stress first increased to a maximum and then decreased to a steady state. It indicated that the dynamic competition took place between the working hardening and working softening during hot compression. Moreover, the main deformation mechanism was twining at strain of 0.08 for the as-solution alloy; with the increase of the strain, dynamic recrystallization (DRX) grains appeared at original grains and twins boundaries. Lots of nanoscale I-phase which pined and hindered dislocation precipitated within the matrix during hot compression process.

Abstract: A study was made of the effects of solid solution treatment on the properties of hot rolled Fe-Mn-Al steel and on the microstructure transformation. In the steel, the austenite matrix and ferrite duplex phases were confirmed by micrographs and X-ray diffraction. It was indicated that the hot rolled Fe-Mn-Al steel (6.55g/cm³ in density) is with mechanical properties of tensile strength 1315.6MPa, elongation 14.60%. The tensile strength decreases with increasing temperature. The tensile test displays an outstanding combination of high strength and ductility at room temperature due to continuous strain hardening behavior. The product of tensile strength and ductility can reach 46.5GPa·%. Solution treatment contributes to the dissolution of precipitate, austenite grain growth and banded ferrite crushing.

Abstract: An observation was conducted on the microstructures of as-cast as well as solid solution treated the third generation single crystal superalloy DD9 using optical microscope and SEM. The effects of solid solution temperature and time on the eutectic fractions of γ/γ and size of γ of the alloy were investigated. The results showed that the microstructure of DD9 was uniform. W and Re segregated to the dendrite cores while Al, Ta and Nb were enriched in interdendritic regions during solidification. The eutectic fractions of γ/γ reduced with the solid solution temperature raising and the solid solution time prolonging. When solid solution temperature increased to 1340, the eutectic in the alloy was entirely dissolved. The size of γ in dendritic cores was consistent, however the size of γ in interdendritic regions was gradually decreased with the increase of solid solution treatment and time, eventually the sizes of γ were completely uniform at the temperature of 1340

Abstract: The effects of solid solution treatment on high cycle fatigue behavior of cast magnesium alloy AZ91D were investigated using an up-and-down load method. High cycle fatigue tests were carried out up to 107cycles at a stress ratio R=0.1 and frequency of 90Hz on specimens using a high frequency fatigue machine. The results showed that the fatigue strength of cast AZ91D magnesium alloy increase from 54.5Mpa to 71.5Mpa after solid solution treatment (T4) at 415°C, keeping temperature 16hours. The micro-fatigue fracture surface of alloy included fatigue initiation area, fatigue crack propagation area and fatigue fracture area. Fatigue crack of the alloys initiate principally at inclusions and shrinks under subsurface. The fatigue fracture of test specimens show the rupture characteristics of quasi-cleavage(as-cast alloy) and toughness(T4 alloy), respectively.

Abstract: The Al-Zn-Mg-Cu (7A04) alloys were prepared by using the method of spraying deposition and the hot extrusion. The effects of two-stage solid solution treatment and single solid solution treatment on the microstructure and mechanical properties of spray deposited 7A04 alloy were investigated. The microstructure and mechanical properties were observed and tested by optical microscopy, SEM, X-ray diffraction and other methods. It is indicated that the two-stage solid solution treatment is better than the single. After the two-stage solid solution, the sizes of recrystallization grains were small and a lot of precipitations were dissolved. And the microstructure was nice by ageing treatment. The tensile strength and elongation of the alloy can respectively reach 740MPa and 5.8 percent by the two-stage solid solution (at 450°C for 1 hour and 475°C for 2 hours) and the aging treatment.

Abstract: Automotive castings have to meet more and more versatile requirements these days. One of the most important requirements towards suppliers and foundries is producing parts of better quality, higher performance but at the same time of less weight. In order to couple this small weight with high performance and excellent quality these products should meet very strict mechanical standards of automotive parts. There is a constant need for production engineering developments ranging from purity degree - that is producing molten metal with high cleanness - to grain refinement and alloy improving including heat treatment technologies.

Abstract: Effect of solid solution treatment on corrosive behavior of 00Cr26Ni5Mo2Cu3Re Duplex Stainless Steel in static stage of HNO₃+HF acid solution is studied in the paper.The results show that the corrosion between phases and pitting corrosion on ferrite are serious at low temperature ,the phenomenon gradually disappear with the solid solution temperature rising ; the corrosive resistance of 00Cr26Ni5Mo2Cu3Re is getting better first and then decrease with solution temperature at high temperature, the best corrosive resistance temperature is at 1050°C.

Abstract: The coherent fine-lamellae consisting of the 2H-Mg and the 14H-type long period stacking ordered (LPSO) structure within α'-Mg matrix have been observed in an as-cast Mg–Gd–Zn–Zr alloy. During subsequent solid solution heat treatment at 773 K, in addition to the lamellae within matrix, a novel lamellar X phase [Mg–(8.37±1.0)Zn–(11.32±1.0)Gd] with the 14H-type LPSO structure was transformed from the dendritical β phase. The 14H-type LPSO structure existing in Mg–Gd–Zn–Zr alloys derives from two variant ways: formation of the 14H-type LPSO structure comes from two variant means: i.e., the formation within matrix and the phase transformation from the β phase to the X phase in grain boundaries.