Papers by Keyword: Aging Treatment

Abstract: A cold roll-bonding (CRB) process is applied to fabricate a multi-layer Al sheet using AA5052 and AA6061 alloys. The rolling is performed for four-layer sheets in which AA5052 and AA6061 sheets are stacked alternately after surface treatments such as degreasing and wire brushing. The 4-layer sheets with a thickness of 8 mm were roll-bonded to 2 mm by rolling at total reduction of 75%. The as roll-bonded Al sheets are then processed by natural aging (T4) and artificial aging (T6) treatments. T4 and T6 treated specimens showed a typical recrystallization structure over all regions of AA5052 and AA6061. The average grain diameter of T4 and T6 specimens was about 15 μm, which is almost the same. In addition, the Al sheet showed a heterogeneous hardness distribution in thickness direction. After the aging treatments of T4 and T6, the strength rather decreased and the elongation increased. It is found that new multilayer Al sheets made of AA6061 and AA5052 alloys, exhibiting various mechanical properties can be fabricated through the CRB and subsequent aging treatments.

Abstract: A test probe is used for continuity test of semiconductor packages with solder balls. The probe material is often damaged due to solder adhesion on it by repeated test. The Pd-42Cu-10Ni (mass%) alloy has been developed as a substitute material for the conventional Pd-30Cu-29.5Ag-0.5Zn (mass%) alloy. The interfacial reaction between Pd-42Cu-10Ni and Sn by aging at 150°C was investigated in this study. Moreover, the obtained data was compared to those of the conventional alloy. As a result, it was confirmed that granular (Cu,Ni)₆Sn₅ forms at the interface between the reaction layer and Sn, and the reaction layer consists of stacked layers of the PdSn₄+PdSn₃ layer and the (Cu,Ni)₆Sn₅+Cu₃Sn+PdSn layer. The reaction layer mainly grew toward the Sn side from the original interface. Furthermore, the thickness of the reaction layer grown by aging was suppressed to approximately one-fourth compared with the conventional alloy.

Abstract: β-Ti alloys have been increasingly explored for biomedical applications due to their attractive combination of mechanical properties, including low elastic modulus, high tensile strength, good fatigue resistance, excellent ductility, and superior corrosion resistance. In this context, and building upon previous research, a metastable β-Ti alloy, Ti-12Mo-13Nb, was developed via hot forging as a potential alternative to the conventional Ti-6Al-4V alloy. This study investigates the microstructure and mechanical behavior of the Ti-12Mo-13Nb alloy processed by hot swaging, followed by aging at 500 °C for 10 min, 4 h, and 24 h. Phase transformations were analyzed using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Mechanical characterization was carried out through Vickers microhardness testing and Young’s modulus measurements. The highest microhardness-to-modulus ratio was achieved after aging at 500 °C for 24 h, corresponding to a microstructure composed of fine α precipitates uniformly distributed within the β matrix.

Abstract: Due to its high strength, excellent electrical conductivity and high resistance to stress corrosion, Cu-Ni-Sn alloy has been selected as a kind of advanced metal material which can be used as the manufacture of springs, connectors, bearings and so on. In addition, the addition of Nb can efficiently improve the comprehensive properties of the alloy. In the present work, the effect of heat treatment conditions on microstructure and mechanical properties were studied in a Cu-9Ni-6Sn-0.22Nb alloy by means of optical microscopy (OM), transmission electron microscopy (TEM), tensile test and microhardness tests. The results show that before ageing, a large number of fine γ precipitates with DO₂₂ type structure are distributed on the matrix. With the prolongation of ageing time, the ultimate tensile strength (UTS), yield strength (YS) and Vickers hardness increased firstly, and then decline. The reason can be attributed to the occurrence of spinodal decomposition and the formation of discontinuous precipitation (DP). At first, spinodal decomposition induced the enhanced interaction between dislocations and internal stress field, resulting in an increase of mechanical properties. Then the increased DP at grain boundaries leads to the decline of strength in the material. Finally, the relationship between the microstructure and the electrical conductivity was also analyzed, and the results show that the electrical conductivity increased with ageing time/ageing temperature increasing for the present alloy. Through the analysis of Matthiessen’ s rule, the variation of electrical resistivity depends on precipitates, solute atoms, dislocations, vacancies and grain boundaries, and the precipitates play an important role among them. Besides, more precipitates improve electrical conductivity. Therefore, the increase of ageing time/ageing temperature induced the increase of DP, resulting in an increase of electrical conductivity.

Abstract: The novel titanium alloys were investigated in this article. The Ti-3573 and Ti-3873 titanium alloys were cold rolled and aged for different times at 650°C. The microstructure and mechanical properties of the samples were observed and measured, respectively. The results show that the mechanical properties of Ti-3873 alloys were better than those of Ti-3573 alloys. The cold rolling accelerated the α phase precipitation effectively. Stress-induced martensitic transformation was observed in both titanium alloys after cold rolling and aging treatment. Better aging strengthening effect can be obtained for the Ti-3873 titanium alloy which contains more molybdenum element, it is attributed to the role of Mo as β phase stable elemen. The tensile strength of Ti-3873 titanium alloy after aging for 3h reached the maximum value (1314MPa).

Abstract: Beta titanium alloys have several attractive features; this has resulted in this group of alloys receiving much attention since 1980’s. Among the attributes which distinguish them for their superiority over other structural materials are (i) high strength to which they can be heat treated, resulting in high strength to weight ratio (ii) high degree of hardenability which enables heat treatment in large section sizes to high strength levels (iii) excellent hot and cold workability, making them as competitive sheet materials etc. The standard heat treatment consists of solution treatment in beta or alpha plus beta phase field followed by aging. However, certain aging treatments can render the materials in a state of little or no ductility; the designer has to be aware of this behaviour and has to keep away from such treatments while working with the materials. Such unfavourable aging treatments may adversely affect not only the static properties such as reduction in area and elongation in a tensile test, but also dynamic properties such as impact toughness. Results of fractographic studies are in line with those of mechanical testing. The authors would present the foregoing analysis, based primarily on the wide-ranging researches they carried out on beta titanium alloy Ti15-3 and to some extent data published by researchers on other grades of beta titanium alloys. An attempt is made to explain the mechanisms underlying the embrittlement reactions that take place in beta titanium alloys under non-optimal aging treatments.

Abstract: The effect of Ca and Zr Additions and Aging Treatments on Microstructure and Mechanical Properties of Mg-Sn alloy was investigated. It was found that the grain size of as-cast Mg-4Sn-xCa and Mg-4Sn-xZr alloys was refined with the increase of alloying elements addition. The alloys were solution-treated at 480 °C and aged at 160 °C, and the aging peak appeared after 4-5 h. The difference was that the maximum tensile strength and Brinell hardness of Mg-4Sn-0.3Ca were 140.7 MPa and 44.5 HB, respectively, while in Mg-4Sn-xZr alloy, Mg-4Sn-0.5Zr was optimal. The maximum tensile strength and Brinell hardness of Mg-4Sn-0.5Zr were 137.4 MPa and 41.5 HB, respectively. This difference was mainly due to the formation of the brittle phase CaMgSn in the Mg-4Sn-xCa alloy. The excessive brittle phase was not conducive to the strength of the alloy, but could increase the hardness of the alloy. However, Zr existed as a simple substance in the alloy, which can be used as a nucleation particle to inhibit grain growth and play a role of fine grain strengthening. But the addition of Zr did not form many hard phases, so the hardness did not change much.

Abstract: In this paper, the study of precipitation reaction in the aluminum alloy known as AGS 6101. For the case of Cold drawn wires process in the open air space and at room temperature for two years, we inspect first the presence of precipitates in the microstructure and study the effect of heat treatment on the activation of this phenomenon [1]. The second objective of this work is to see the effect of natural and thermal aging on the microstructural evolution of cold-drawn aluminum wires (AGS) 6101 [2-5]. The characterization methods used in this work are optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction.

Abstract: Through a series of mechanical properties tests and microstructure observation, the effects of artificial heat treatment (AA), pre-stretching aging (PA) and pre-stretching creep aging (PCA) treatment on the precipitation phase type and mechanical properties of X2A66 aluminum-lithium alloy were studied. The results show that compared with AA, PA treatment promotes the uniform precipitation of high-density T₁ phase, so that the yield strength, tensile strength and elongation of the alloy reach 593.4Mpa, 610.8Mpa, 10.7%. Further, the creep aging treatment on the basis of the pre-deformation can further increase the strength (613.6Mpa, 628.9Mpa) of the alloy with a slight decrease in the elongation (10.3%).

Abstract: The Cr precipitation sequence in Cu-Cr-Zr-Ag alloy during the aging process at 450°C could be obtained by Transmission electron microscopy (TEM) and High-resolution transmission microscopy (HRTEM) in the study. The strengthening curve shows a unimodal type and the tensile strength trends to peak when the aged for 4h. The Cr phase transformation of Cu-Cr-Zr-Ag aged at 450°C is supersaturated solid sloution→G.P zones→fcc Cr phase→order fcc Cr phase→bcc Cr phase. The orientation relationship between bcc Cr precipitates and the matrix change from cube-on-cube to NW-OR.