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Forging of Titanium
Abstract
IntroductionGeneral Properties and ApplicationsThermomechanical Treatment of Titanium Alloys Processing of Forging StockForgingsHeat TreatmentProcess Design Geometric RequirementsForged Components and Forging EquipmentProcessing Window for ForgingsFinite Element SimulationExamples for Process Optimization and ApplicationsReferenced Literature and Further Reading Processing of Forging StockForgingsHeat Treatment Geometric RequirementsForged Components and Forging EquipmentProcessing Window for ForgingsFinite Element Simulation
... can heat-treatment ( Terlinde et al. 2003; Wagner 1997; Evans 1999). However, it has long been recognized that annealing of Ti-6Al-4V, although it significantly reduces the strength, is beneficial to the DTD-related properties of long/large fatigue crack growth, fracture toughness and stress corrosion cracking resistance (Paton et al. 1976). ...
The most important fields, in which titanium and titanium alloys are on large scale, used are: aerospace construction industry, military technique, chemical and oil equipment industry, ship construction industry, human medicine, etc. The most important properties, which determine the titanium and titanium alloys use in different applications are:-high mechanical resistance at high or law temperatures;-specifically mechanical resistance (mechanical resistance / density) greater than for other materials (Rm/ : 22-27 for Ti alloys; 10-13 for Al alloys; 16-23 for steels);-high corrosion resistance, in different media (sea water, acids and acids solutions, ammonia, sulphur, etc.) [1]. Some examples for titanium and titanium alloys applications: a. Aerospace constructions
Metastable beta titanium alloys have emerged as a subject of intense research in the last three to four decades. They are epitomized by heat treatability to high strength, high hardenability, and excellent workability. Heat treatment comprises solution treating and aging. In the recent years, there has been much interest in carrying out aging in two steps, rather than in a single step. Duplex aging on different grades of beta alloys resulted in improved microstructure and better combination of mechanical properties. Duplex aging suppresses formation of grain boundary alpha and eliminates precipitate-free zones, leading to improved ductility and fatigue life. There is thus a strong case to adopt duplex aging. A low heating rate to aging temperature may be tantamount to duplex aging. There are a few grades, where duplex aging impairs ductility, becoming counterproductive. The paper reviews the subject of duplex aging of metastable titanium alloys.
Low-cost-type Ti-14Mn-(x)Zr (x = 0, 3, or 6 wt%) alloys were developed and prepared using single-electrode arc furnace, and the effects of the zirconium (Zr) content and thermomechanical treatment on the phase stability, microstructural evolution, hardness, compressive stress, and corrosion resistance of the alloys were studied. The alloy thickness was reduced by approximately 45% by hot forging at 900 °C and were then water quenched and subsequently aged at 500 or 700 °C for different times. The combination of the proper Zr content, hot forging, and aging improved the alloy hardness, strength, and ductility. The dual (α + β) structure formed in the 6Zr alloy forged and then aged at 700 °C for 60 ks resulted in a high compressive yield stress of 1127 MPa and malleability above 70%. The forged and annealed alloys exhibited superior properties to commercial Ti-6Al-4 V (lower cost, corrosion resistance, and mechanical properties). The study findings elucidate the relationship between the composition and processing properties of low-cost Ti-14Mn-(x)Zr alloys for potential biomedical applications.
Titanium alloys have been successfully used in the energy industry due to their stability at high temperature service, good mechanical properties and corrosion resistance. The near-α Ti-6%Al-1.5%V-1.0%Mo-0.5%Zr-0.1%C alloy, has been successfully used in several parts for geothermal energy generation. Several studies have concluded that the wear behavior of Ti alloys is generally poor; however, the specific tribosystem must be analyzed. This work analyzes the additions of 0.3%Ru, and variations of the V and Mo contents on the wear performance of a Ti alloy. Different combinations of α+β and degrees of microstructural refinement were observed depending on the composition. Wear test were undertaken by using a dry sliding block-on-ring configuration under the ASTM G77 standard. Two different loads (7 and 25 N) were used against a M2 hardened steel ring as a counter face with a hardness of 790 HV. Results showed that for the 7N load, the wear behavior is related to the volume fraction and thickness of the α phase; on the other hand, for the 25N load tests, the wear losses are directly proportional to the bulk hardness of the alloys and the α plate thickness, for this condition, best wear performance was achieved by the alloy 3 which contains 1.0wt%V, 1.8wt% Mo and 0.25wt% Ru. From the experimental results of the present study, it has been found that the wear behavior is directly related to the microstructure, e.g. amount of phases, refinement degree, applied load, and, in a lesser extent to the bulk hardness.
TC4 alloys with equiaxed and Widmanstätten initial microstructures were compressed at 700-800°C in a strain rate of 100s-1. Flow oscillations are observed regardless of the initial microstructures. For equiaxed initial structure continuous DRX of α grains is the main softening mechanism, and the degree of continuous DRX is scarcely influenced by the temperature. For lamellar initial structure the dominant softening mechanism changes with the temperature. The degree of α globularization increases with increasing temperature. The microstructure can be refined effectively by the combination of continuous DRX and dynamic globularization of α grains (or plates).
Polycrystalline pure titanium was irradiated by high-current pulsed electron beam (HCPEB). The microstructure changes and material strength were investigated by using microhardness tester, optical microscope, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) technique. The experimental results indicate that many craters are inevitably formed on the irradiated surface. The eruption of the craters makes the material surface cleaned, which can improve the corrosion resistance of materials. Furthermore, martensitic structure, ultra-fine grains and high-density dislocations are formed on the irradiated surface, which increase the hardness of the treated samples. The microhardness of 20-pulsed sample reaches 286Hv, which is 71% higher than the initial sample. Martensitic transformation, grain refinement and dislocation strengthening induced by HCPEB treatment are the dominating mechanism for the improvements of material strength. It is suggested that HCPEB technique is becoming an effective approach to surface modification for pure titanium and titanium alloy.
The grain size of as-cast Ti–6Al–4V is reduced by about an order of magnitude from 1700 to 200 μm with an addition of 0.1 wt.% boron. A much weaker dependence of reduction in grain size is obtained for boron additions from >0.1% to 1.0%. Similar trends were observed in boron-modified as-cast Ti–6Al–2Sn–4Zr–2Mo–0.1Si.
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