Microstructure and Mechanical Properties of Carbides Reinforced Nickel Matrix Alloy Prepared by Selective Laser Melting

Selective laser melting was used to prepare the ceramic particles reinforced nickel alloy owing to its high designability, high working flexibility and high efficiency. In this paper, a carbides particles reinforced Haynes 230 alloy was prepared using SLM technology to further strengthen the alloy. Microstructures of the carbide particles reinforced Haynes 230 alloy were investigated using electron microscopy (SEM), electron probe microanalysis (EPMA) and transmission electron microscopy (TEM). Meanwhile, the tensile tests were carried out to determine the strengths of the composite. The results show that the microstructure of the composite consisted of uniformly distributed M23C6 and M6C type carbides and the strengths of the alloy were higher than the matrix alloy Haynes 230. The increased strengths of the carbide reinforced Haynes 230 alloy (room temperature yield strength 113 MPa increased, ~ 33.2%) can be attributed to the synergy strengthening including refined grain strengthening, Orowan strengthening and dislocation strengthening.

Technical Basis for Expansion of ASME BPVC Section XI, KIC Curve Applicability

When the Appendix G methodology, fracture toughness criteria for protection against failure, was first adopted by ASME Section III in 1972, it included a lower-bound Kir curve for ferritic steels with specified minimum room-temperature yield strength up to 50 ksi. In 1977, Section III Appendix G added a requirement to obtain fracture-toughness data for at least three heats (base metal, weld metal, and heat-affected zone) if the KIR curve is used for ferritic steels with specified minimum room-temperature yield strength between 50 and 90 ksi. The three-heat data requirement has not changed when the lower bound curve was adopted by Section XI, or when the lower-bound crack initiation toughness curve was changed from the dynamic Kir curve to the static KIc curve during the 2000s. Based on the accumulation of fracture-mechanics data of ferritic steels with specified minimum yield strength between 50 ksi and 90 ksi and their use for Class 1 pressure vessel production, Section XI recently expanded the applicability of the KIc curve to SA-508 Grade 2 Class 2, SA-508 Grade 3 Class 2, SA-533 Type A Class 2, and SA-533 Type B Class 2 whose specified minimum room-temperature yield strength is 65 ksi or 70 ksi. This paper describes the technical basis including the fracture-mechanics data to support the expansion of the applicability of the KIc curve by ASME Section XI.

Influence of Chemistry on the Tensile Yield Strength of Nickel-Based Single Crystal Superalloys

The tensile yield strength of AM1 and MC-NG single crystal superalloys with a γ’ precipitate size close to 300 nm were compared within the 20-1050°C temperature range. The room temperature yield strength of the fourth generation MC-NG superalloy is about 200 MPa less than that of the AM1 first generation one. Inversely, at higher temperatures (T > 800°C), the tensile strength of MC-NG is higher than that of AM1. These results are discussed by taking into account the elementary deformation mechanisms and the respective strengths of the γ and γ’ phases. Experiments on a modified MC-NG alloy show that reinforcing the γ’ phase by increasing the contents of Ti and Ta is an efficient way to recover a higher tensile strength at low temperatures. Rhenium addition and increase of the γ’ solvus temperature are suggested to be beneficial for the high temperature tensile strength. Data published on various other single crystals are in agreement with these hypotheses.

Effects of Cooling Rate on the Microstructure and Room Temperature Tensile Properties of Orthorhombic Ti-22Al-21Nb-1Ta-1W Alloy

In order to improve high temperature mechanical properties of Ti2AlNb based alloys, alloying with a combination of Ta and W was studied in the on-going work. The effects of cooling rate after solution heat treatment on the room temperature mechanical properties have been reported in this paper. All samples were solid solution treated at near β transus temperature, cooled at different cooling rates, and then aged at subtransus temperature. Experimental results showed that, with increasing cooling rate, room temperature yield strength decreased sharply to a minimum value, and then increased. Change of elongation exhibits a trend opposite to yield strength. Microstructure of the alloy varied from near lamellar to lamellar plus Widmanstätten, and then to full Widmanstätten structure with the increase of cooling rate, and the faster the cooling rate, the finer the laths of the O phase. The samples with near lamellar microstructure obtained at the cooling rate of 6oC/min possess the best ductility but relatively low yield strength.

ARMCO NITRONIC 40

ARMCO NITRONIC 40 Stainless Steel is one of the most versatile austenitic stainless steels with a room-temperature yield strength about twice that of AISI Types 304, 321 and 347. In addition, NITRONIC 40 has remarkably good elevated temperature properties and oxidation resistance. It retains high toughness down to -423 F. This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as fracture toughness and creep. It also includes information on low temperature performance and corrosion resistance as well as forming, heat treating, and joining. Filing Code: SS-327. Producer or source: Armco Advanced Materials Corporation. Originally published as Nitronic 40, May 1976, revised August 1990.

RMI 6Al-ELI

RMI 6A1-4V ELI is an alpha-beta type of titanium-base alloy that can be strengthened by age hardening. In the mill-annealed condition it has a guaranteed minimum room-temperature yield strength of 120,000 psi and can be increased to as much as 160,000 psi by solution treating and aging. This alloy may be used for high-pressure cryogenic vessels down to 320 F. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and bend strength as well as fracture toughness. It also includes information on corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: Ti-89. Producer or source: RMI Company.

RMI 6Al-4V

RMI 6AI-4V is an alpha-beta type of titanium-base alloy that can be strengthened by age hardening. In the mill-annealed condition it has a guaranteed minimum room-temperature yield strength of 120,000 psi and this can be increased to as much as 160,000 psi by solution treating and aging. This alloy is tough and has attractive elevated-temperature properties. It is used widely for applications at temperatures up to 800 F. Typical applications are parts for jet engines, aircraft components and pressure vessels. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and bend strength as well as fracture toughness and creep. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: Ti-88. Producer or source: RMI Company.

Observation of slip propagation across grain boundaries in Ni3Al

Recent modelling of the grain size dependence of the room-temperature yield strength of Ni3Al has invoked the concept of dislocation pile-ups. The idea is that the yield strength measured in the Liiders regime (i.e. the Liiders band propagation stress) represents not the stress to independently nucleate slip in each grain but the stress required to propagate slip through the material. This paper presents direct evidence of slip propagation from one grain to the next and thus validation of the use of a pile-up model for Ni3Al.Miniature tensile specimens (3 mm x 7 mm x0.2 mm), made from an extruded rod of fine-grained (∽10 μm) Ni3Al containing 0.35 at.% boron, were strained under tension whilst being observed in a Philips EM 430T operated at 300 KV. Details of the design and operation of the straining stage and of the specimen preparation techniques are given elsewhere.

Precipitation Strengthening Of Rapidly Solidified Austenitic Stainless Steels

ABSTRACTPrecipitation kinetics was studied in a rapidly solidified 316 stainless steel containing 0.22% C and 1% Ti. A high density of fine TiC particles was obtained by annealing at 923 to 973 K. An increase in recrystallization temperature and room temperature yield strength was observed as compared with the rapidly solidified 316 stainless steel with a nominal carbon and titanium content. An extension of solid solubility by rapid solidification thus offers a potential for developing precipitation strengthened austenitic stainless steels to improve structural and mechanical stability and likely the irradiation resistance.

RMI 5Al-5Sn-2Zr-2Mo-Si

RMI 5A1-5Sn-2Zr-2Mo-Si is an alpha-type titanium alloy recommended for high-temperature applications in the 800-1000 F range. In the mill annealed condition it has a typical room-temperature yield strength of 126,000 psi and a typical yield strength (in short-time elevated-temperature tensile test) of 80,000 psi at 1000 F. Its uses include elevated-temperature service and jet-engine components. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness and creep. It also includes information on corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: Ti-78. Producer or source: RMI Company.