Showing papers on "Charpy impact test published in 1980"
TL;DR: In this article, a simple expression for the dynamic stress intensity factor of a pre-cracked Charpy specimen is derived by making use of an approximate solution for one-dimensional beam equations.
82 citations
TL;DR: In this paper, a thermal treatment which combines grain refinement with an intercritical temper (the 2BT treatment) was used to achieve a promising combination of strength and toughness in a nickel-free ferritic steel of nominal composition Fe-5Mn-0.2Mo- 0.04C at temperatures as low as -196 °C.
Abstract: It is shown that a thermal treatment which combines grain refinement with an intercritical temper (the 2BT treatment) may be used to achieve a promising combination of strength and toughness in a nickel-free ferritic steel of nominal composition Fe-5Mn-0.2Mo-0.04C at temperatures as low as -196 °C. The properties achieved are attributed to a symbiotic influence between the grain refinement treatment and the introduction of thermally stable retained austenite during intercritical tempering, a conclusion supported by a comparison of the results to those obtained with simpler heat treatments. The influence of carbon, manganese, and nickel additions to the base compositions are studied. An increase in carbon content above 0.04 wt pct causes a deterioration in toughness, as does an increase in manganese to 8 wt pct. An addition of 1 to 3 wt pct nickel is beneficial giving an increase in alloy strength at -196 °C without loss of toughness.
67 citations
TL;DR: In this paper, it was concluded that the formation of thermally stable retained austenite is beneficial to the fracture toughness of Ni steels at 77 K as a result of Austenite gettering carbon from the matrix during tempering.
Abstract: Heat treatments were utilized in 5Ni and 9Ni steel which resulted in the development of tempered microstructures which contained either no measurable retained austenite (<0.5 pct) or approximately 4 to 5 pct retained austenite as determined by X-ray diffraction. Microstructural observations coupled with the results of tensile testing indicated that the formation of retained austenite correlated with a decrease in carbon content of the matrix. Relative values ofKIC at 77 K were estimated from slow bend precracked Charpy data using both the COD and equivalent energy measurements. In addition, Charpy impact properties at 77 K were determined. In the 9Ni alloy, optimum fracture toughness was achieved in specimens which contained retained austenite. This was attributed to changes in yield and work hardening behavior which accompanied the microstructural changes. In the 5Ni alloy, fracture toughness equivalent to that observed in the 9Ni alloy was developed in grain refined and tempered microstructures containing <0.5 pct retained austenite. A decrease in fracture toughness was observed in grain refined 5Ni specimens containing 3.8 pct retained austenite due to the premature onset of unstable cracking. This was attributed to the transformation of retained austenite to brittle martensite during deformation. It was concluded that the formation of thermally stable retained austenite is beneficial to the fracture toughness of Ni steels at 77 K as a result of austenite gettering carbon from the matrix during tempering. However, it was also concluded that the mechanical stability of the retained austenite is critical in achieving a favorable enhancement of cryogenic fracture toughness properties.
58 citations
TL;DR: In this paper, a better evaluation of the ductile fracture resistance of rising shelf controlled rolled steels than Charpy energy can be made by using the drop weight tear test (DWTT) energy at the service temperature.
30 citations
TL;DR: In this paper, the problem of obtaining a meaningful value of toughness from small Charpy-size surveillance specimens, tested at temperature corresponding to the upper shelf where ductile fracture predominates, is investigated.
Abstract: The problem of obtaining a meaningful value of toughness from small Charpy-size surveillance specimens, tested at temperature corresponding to the upper shelf where ductile fracture predominates, is investigated. Following the procedures of Green and Knott for measurement of crack opening displacements at initiation of ductile fracture, a test procedure is adopted in which small precracked Charpy-size bend specimens are side-grooved to increasing depths and tested to failure under both quasi-static and dynamic loading rates. Values of the J-contour integral at maximum load (J max) for specimens side-grooved in excess of 30% are found to agree, within acceptable limits, with valid initiation J(Ic) fracture toughness values determined independently using multispecimen resistance-curve techniques. Three nuclear pressure vessel materials were evaluated at temperatures between 71 and 177 C, which correspond to upper shelf temperatures. The test procedure described offers a simple, inexpensive, small specimen compromise for estimating the fracture toughness at the onset of ductile fracture from a single Charpy-size bend test piece for both quasi-static and dynamic loading rates. This approach could be readily adopted in nuclear surveillance programs for toughness evaluation of unirradiated and neutron-irradiated pressure vessel steels.
26 citations
TL;DR: The scavenging effect of precipitated austenite in a low carbon, commercial Fe-5.5Ni cryogenic alloy was investigated through observation of the dissolution of cementite precipitates during intercritical tempering and study of the associated change in Charpy impact toughness.
Abstract: The scavenging effect of precipitated austenite in a low carbon, commercial Fe-5.5Ni cryogenic alloy was investigated through observation of the dissolution of cementite precipitates during intercritical tempering and study of the associated change in Charpy impact toughness. Cementite precipitates initially located along prior austenite grain boundaries were gradually dissolved into reverted austenite as the intercritical tempering proceeded. The austenite tends to form at or around the carbide particles and may be catalyzed by their presence. The Charpy impact energy is changed through both a decrease in the ductile-brittle transition temperature and an increase in the upper shelf energy. The latter effect is specifically associated with the dissolution of the carbides which act as preferential void nucleation sites in the untempered alloy.
22 citations
TL;DR: In this article, impact bending tests of 0.45% carbon steel were carried out on U-notched annealed specimens and quenched-and-tempered ones.
Abstract: By using a split Hopkinson bar type apparatus, impact bending tests of 0.45% carbon steel were carried out on U-notched annealed specimens and quenched-and-tempered ones. The load-deflection curves were determine easily by the tests. The temperature dependences of the yield load, the maximum load, the fracture load and the absorbed energy were determined within the temperature range from room temperature to -195°C. The absorbed energies agree fairly well with the ordinary Charpy values at these temperatures for both specimens. Repeated impact bending tests with a short striker bar were also carried out and it has become clear that the crack initiates at or slightly beyond the maximum load.
20 citations
16 citations
TL;DR: In this paper, the impact behavior of a low-density polyethylene was studied with an instrumented Charpy tester, and a change from elastic or ductile response to brittle fracture was observed over a small temperature interval, usually within 1°C.
Abstract: The impact behavior of a low-density polyethylene was studied with an instrumented Charpy tester A change from elastic or ductile response to brittle fracture was observed over a small temperature interval, usually within 1°C This characteristic impact transition temperature (ITT) was highly sensitive to shallow, sharp notches Whereas an unnotched test bar had a very low impact transition temperature of −94°C, a razor cut with a depth of only 5 percent of the total thickness raised it to −4°C The impact transition temperature was effectively reduced by increasing the cooling rate during specimen preparation and by the addition of nonpolar liquids, On the other hand, impact properties were adversely affected by aging, annealing, and adding other thermoplastics
15 citations
TL;DR: In this article, a fracture mechanics approach was adopted to measure meaningful values of material toughness, and the results obtained in bending are consistent with those in tension, and a discussion of the assessment of kinetic energy errors was also presented.
Abstract: Charpy and tensile impact tests have been conducted on two materials poly(methyl methaerylate) (PMMA) and polycarbonate. It is shown that by adopting a fracture mechanics approach, it is possible to measure meaningful values of material toughness, and that the results obtained in bending are consistent with those in tension. A discussion of the assessment of “kinetic energy” errors is also presented.
14 citations
TL;DR: In this paper, the AISI 4340 steel has been electroslag refined and the improvement in mechanical properties has been assessed, which has shown that the ESR steel has a better response to heat treatment.
TL;DR: In this paper, a reference curve was developed for nuclear pressure vessel steel on the basis of a set of precracked instrumented Charpy V-notch tests, and the reference curve can be readily used to define a lower bound relationship between fracturemore-toughness and temperature.
Abstract: A large base of K/sub IC/, K/sub Id/ and J/sub IC/ (R-curve) fracture toughness data has been used to develop reference toughness curves. The most successful results were obtained when a sigmoidal function was fitted to data from which the heat-heat variation in both the temperature and fracture toughness had been reduced by referencing. Several referencing procedures have been studied, but the only one found to be successful in this work was based upon the precracked instrumented Charpy V-notch test. The tanh function K = A + B tanh (T - To/C) (K = toughness, T = temperature, and A, B, T/sub 0/ and C are coefficients which give the best fit between curve and data) fitted to precracked instrumented Charpy V-notch test data provided suitable referencing quantities. Using the coefficients A and B to reference fracture toughness, and T/sub 0/ and C to reference temperature, lower bound reference curves were developed. Weighted, nonlinear regression procedures were used to define lower bound reference toughness curves for each of three stress intensification rates. The lower bound was the statistical global tolerance bound to the referenced data. The reference curves can be readily used to define a lower bound relationship between fracturemore » toughness and temperature for nuclear pressure vessel steel on the basis of a set of precracked instrumented Charpy V-notch tests.« less
TL;DR: In this paper, the effect of tin on the toughness of six common plate, structural, linepipe, and rail steels containing zero to 0.25 pct tin was investigated.
Abstract: The primary purpose of this investigation was to determine the effect of tin on the toughness of six common plate, structural, linepipe, and rail steels containing zero to 0.25 pct Sn. To put the changes in toughness into better perspective, the effect of tin on tensile properties was also noted. The effects of tin on Charpy transition temperatures and shelf energy are dependent on steel grade or a combination of grade and heat treatment; for example, an increase of 0.01 pct Sn increased the 20 J transition temperature by zero to 2.3°C. Contrary to the case for transition temperature, the effects of tin on tensile properties do not depend on steel grade or a combination of grade and heat treatment. The tensile effects in the present study were found to be consistent with those noted in previous literature cited in the paper. A mechanism to explain the effect of tin on toughness is considered.
Patent•
12 Jul 1980
TL;DR: In this article, the welding rod of good impact toughness such as Charpy and crack opening displacement amount (COD value) which is obtainable by adding respectively suitable amounts of Mn and B to the core wire and Ti and further one or more kinds of Al, Mg, Zr and Ca to the coating agent.
Abstract: PURPOSE:The captioned welding rod of good impact toughness such as Charpy and crack opening displacement amount (COD value) which is obtainable by adding respectively suitable amounts of Mn and B to the core wire and Ti and further one or more kinds of Al, Mg, Zr and Ca to the coating agent. CONSTITUTION:The low alloy steel core wire which contains Mn; 1.6-2.4%, B; 0.004-0.02% as essential components and further N; 0.006% or less is prepared. Next, the coating agent composed of Ti; 0.5-8%, total of one or more kinds of Al, Mg, Zr and Ca; 0.2-8%, Si; 1-8%, total of one or more kinds of CaCO3, MgCO3 and BaCO3; 7-58%, total of one or more kinds of CaF2, MgF2, AlF3, Na3AlF6; 1-30% and the rest of slag forming agent, arc stabilizing agent and binder is coated around this core wire. If welding is done by using the low hydrogen type coated electrode obtainable as a result of this, then the weld metal of good imact toughness at low temperature and COD value may be obtained and contribution made to the stability of low temperature tanks or other structures.
Journal Article•
TL;DR: In this article, the ASME Boiler and Pressure Vessel Code specifies the half bead method for carbon steel or low alloy steel weld repairs in case post weld heat treatment (SR) is impractical.
Abstract: ASME Boiler and Pressure Vessel Code specifies the half bead method for carbon steel or low alloy steel weld repairs in case post weld heat treatment (SR) is impractical. A study was made to identify the appropriate procedure for the half bead method applied to repairs for forged low alloy steel (JIS G3212 SFVV 2). As the most recommendable practice, the conclusion suggests that the upper portion of the 1st layer welded by 2.6 mm diameter electrodes is ground off leaving the remainder approximately 2.0--2.5 mm thick from the groove surface prior to the 2nd layer deposition. Parts repaired by the described half bead method were tested in terms of tension, bend, hardness, metallogrphy, V-notch Charpy impact, fracture toughness, fatigue crack initiation and fatigue crack growth rate. These various properties of the rapair parts are comparable to those of repairs with the conventional SR, and particularly the method is found to be significantly effective in avoiding the degradation in toughness of the heat affected zone.
TL;DR: In this paper, isothermal transformation characteristics were determined using dilatometric and thermo-electric potential techniques, and micro-structural features were observed using optical and transmission electron microscopy for treatments of interest following isothermal austenite decomposition in the 550 to 750° C range.
Abstract: Investigations of austenite decomposition have been undertaken in (1) Fe-0.5Mn-1V-0.2C and (2) Fe-0.5Mn-3Ni-1V-0.2C alloys. Isothermal transformation characteristics were determined using dilatometric and thermo-electric potential techniques. Also, micro-structural features were observed using optical and transmission electron microscopy for treatments of interest following isothermal austenite decomposition in the 550 to 750° C range. Associated mechanical properties were measured with emphasis being placed on Charpy impact behavior. Both alloys exhibited two temperature regions in which “C-curve” austenite decomposition occurred. In the upper region a combination of fibrous and fine particle VC precipitation was observed in both alloys. In the lower transformation region, bainitic microstructures resulted from the isothermal treatments. Additionally, the alloy containing 3 pct Ni exhibited VC precipitation in the austenite prior to ferrite formation. In both alloys, complete isothermal transformation produced microstructures with poor impact properties. However, a good combination of strength and toughness was produced in the 3 pct Ni alloy using the heat treatment that promoted VC precipitation in austenite but avoided total isothermal austenite decomposition.
TL;DR: In this article, the fracture toughness of 18Cr-2Mo-Nb ferritic stainless steel plates 6, 12, and 25 mm was investigated in the V-notch Charpy test, where the ductile-to-brittle transition temperature is about -30°C.
Abstract: This investigation deals with the practical application of high-purity 18Cr-2Mo-Nb ferritic stainless steel plates 6, 12, and 25 mm thick to welded structures. In the V-notch Charpy test, the ductile-to-brittle transitiontemperature is about -30°C. The fracture toughness, K c , determined by the deep-notch test is 350 kgf/mm 2 . mm for 12-mm-thick plate at -100°C. In the ESSO test, which has a temperature gradient, the K c -value obtained is more than 400 kgf/mm 2 .√mm at 0°C. The toughness of the gas tungsten-arc welded joints using 316 L (C < 0.02 percent) wire deteriorated to some extent, compared with that of the base metal. In the deep-notch test (notch position: fusion boundary, heat-affected zone), however, the K c -value is more than 200 kgy/mm 2 .√ mm at 0°C. It is generally recognized that the safety of a weldable structural steel can be secured if its weld zone has resistance to brittle fracture initiation and the base metal has brittle fracture arresting properties. It can be concluded, therefore, that in thicknesses up to 12 mm this material can be used for welded structures at service temperature above 0°C because of its excellent fracture toughness. Since the toughness of 18Cr-2Mo-Nb deteriorates with aging above 300°C or in cold-working in excess of 10 percent, and even further deteriorates in strain-aging, these effects must be taken into account in its fabrication.
TL;DR: In this article, the effects of precipitates, grain size, plate thickness, and notch sharpness on the Charpy impact toughness of extra-low interstitial 18Cr-2Mo, 26Cr-IMo, and 29Cr2Mo steels were investigated.
Abstract: The effects of precipitates, grain size, plate thickness, and notch sharpness on the Charpy impact toughness of extra-low interstitial 18Cr-2Mo, 26Cr-IMo, and 29Cr-2Mo steels were investigated. The steels exhibit good toughness in the solution-treated condition at 1000 to 1200°C and subsequently in the 2-mm V-notched condition. If the steels are subjected to fatigue cracks or brittle weld cracks, their transition temperatures increase and their shelf energies decrease. When the steels are slowly cooled from the solution temperatures or reheated at intermediate temperatures, 700 to 900°C, after solution treatments, precipitation of second phases occurs, such as Laves phase in 18Cr-2Mo steel and sigma phase in 26Cr-lMo and 29Cr-2Mo steels. The steels are embrittled by these precipitates and behave very similarly to the solution-treated specimens, having sharp notches such as fatigue cracks or brittle weld cracks. A decrease in grain size or thickness is beneficial in lowering the transition temperatures of solution-treated and 2-mm V-notched specimens. This effect, however, decreases, when the specimens have brittle weld cracks. These test results suggest that the solution-treated steels have good resistance to brittle fracture initiation and poor resistance to brittle crack propagation. Precipitation of second phases assists mainly crack initiation but also crack propagation to a lesser extent.
TL;DR: In this article, the effects of refining electroslag refined steel on its mechanical properties have been assessed and it was found that refining caused a decrease in fatigue crack growth rates and increases in fatigue strength, fracture toughness, Charpy fracture energy and tensile ductility.
01 Jan 1980
TL;DR: In this paper, the authors evaluated the relationship between fracture toughness and small-scale test results, such as the Charpy test, the nil-ductility transition temperature test, and the dynamic tear test.
Abstract: Correlations between fracture toughness and small-scale test results are useful due to cost, availability of material, and ease of testing. The material parameter, fracture toughness, can be used directly in design analyses. The small-scale test results, which are not designed to provide the information necessary to predict a failure load or critical flaw size, can provide this information through correlation with the fracture toughness. Possible small-scale tests for this type of relationship include the Charpy test, the nil-ductility transition temperature test, and the dynamic tear test. Correlations of Charpy test results for the upper shelf region and three types of transition region correlations are evaluated. When evaluating the proposed correlations, it is important to consider the effects of notch acuity and strain rate.' The effects of plate position and scatter of the experimental results are also noted. Due to the empirical nature of the correlations, no one correlation can be shown to be more accurate for all materials. A correlation developed for a material under consideration is obviously preferred. When such a correlation is not available, the author has recommended correlations likely to give conservative results. Recommendations for future study are made in order to more thoroughly understand the relationships between fracture toughness and small-scale test results.
TL;DR: In this paper, a new model for the temperature dependence of the fracture toughness has been sought, based on the yielding processes at the crack tip, which are thought to be competitive with fracture.
Abstract: A new model for the temperature dependence of the fracture toughness has been sought. It is based on the yielding processes at the crack tip, which are thought to be competitive with fracture. Using this method a good correlation between measured and calculated values of fracture toughness has been found for a Cr-Mo-V pressure vessel steel as well as for A533B. It has been thought that the application of this method can reduce the number of surveillance specimens in nuclear reactors. A method for the determination of the cleavage fracture strength has been proposed. It can be measured either with low temperature tensile tests or with slow bend tests of Charpy V-notch specimens.
TL;DR: The authors examined the fracture toughness behavior of three heats of A36 steel in terms of Charpy V-notch (CVN) and critical stress intensity level (K 1 c ) at an intermediate rate of loading (that is, one second rise time to failure).
Abstract: This report examines the fracture toughness behavior of three heats of A36 steel in terms of Charpy V-notch (CVN) and critical stress intensity level (K 1 c ) at an intermediate rate of loading (that is, one second rise time to failure). These results are contrasted with current toughness requirements of the American Association of State Highway and Transportation Officials (AASHTO) and the "H" testing frequency.
TL;DR: Fe-26Cr alloys, with and without titanium stabilization, have been studied in an effort to clarify the micromechanisms of brittle fracture in the presence of titanium stabilization and α'-precipitation (475°C embrittlement).
Abstract: Fe-26Cr alloys, with and without titanium stabilization, have been studied in an effort to clarify the micromechanisms of brittle fracture in the presence of titanium stabilization and α'-precipitation (475°C embrittlement) Tension testing, Charpy testing and metallographic evaluations have been undertaken Microscopic observations of electropolished strips pulled in the ductile-to-brittle transition temperature (DBTT) range have been made Titanium stabilization can lead to DBTT increases in low carbon and nitrogen alloys and this embrittlement is associated with intergranular microcrack formation Embrittlement due to α'-precipitation seems related to flow stress increase and the α'-precipitation is seen to bring about a gross change in slip character, leading to the development of relatively few, but extremely intense slipbands
TL;DR: In this article, the authors used the J-R curve approach to evaluate the ductile to brittle temperature performance of a high yield strength structural steel (HY130) and to demonstrate that the single specimen unloading compliance method is applicable to evaluate J Ic values and J R curves for compact specimens tested at temperatures from −192 to 150°C.
TL;DR: In this paper, a micromechanistically based expression is used to predict the cleavage fracture toughness of mild steel as a function of temperature for several different grain sizes, and a method for more accurate determination of the transition is outlined.
TL;DR: In this paper, the fracture mechanism of Zircaloy-4 was studied as a function of orientation, loading rate, and temperature, and the resulting fracture force-displacement curves revealed four distinct segments: (a) elastic deformation, (b) plastic deformations, (c) fracture, and (d) tearing after crack arrest.
Journal Article•
TL;DR: In this paper, the impact transition behavior of commercial heats of three low interstitial vacuum induction melted high-chromium ferritic stainless steels was studied as a function of gage.
Abstract: Impact transition behavior of commercial heats of three low interstitial vacuum induction melted high-chromium ferritic stainless steels was studied as a function of gage. A 50 percent shear fracture (FATT 5 0 ) (fracture appearance transition temperature) of Charpy V-notch impact specimens was used as the transition criterion. E-BRITE alloy, a 26Cr-1Mo alloy, was studied as formerly melted using electron beam refining and as currently melted by vacuum induction melting. With either melting, E-BRITE shows substantially lower impact transition at a given gage than a titanium-stabilized 26Cr-1Mo alloy made to conventional interstitial levels. Gage was observed to affect impact transition, with light gages showing lower FATT 5 0 . Slow cooling from anneal is observed to substantially increase FATT 5 0 in comparison with water quenching. This effect is also seen in the heat-affected zone of welds. Using proper shielding and preparation, however, weld metal and base metal away from the weld show similar transition temperatures. The other two alloys studied are high-purity materials containing 29Cr-4Mo and 29Cr-4Mo-2Ni, respectively. These are similar to E-BRITE alloy in impact behavior with the exceptions (1) that 2 percent nickel can lower water-quenched FATT 5 0 , and (2) that these alloys are sensitive to precipitation of σ and Χ phases. Full-size (10 mm) impact specimens of each alloy can show FATT 5 0 below room temperature if satisfactorily heat-treated.
Patent•
11 Mar 1980
TL;DR: In this article, a low carbon steel is used as a material for a molten slag pan undergoing frequent heat impacts, and the ratio of Mn/C < 7 results in a stable high Charpy impact value.
Abstract: PURPOSE:To provide cast steel with stable Charpy impact value and superior heat check resistance suitable for use as a material for a molten slag pan by holding a specified ratio between C and Mn contained in low carbon steel. CONSTITUTION:As a material for a molten slag pan undergoing frequent heat impacts, cast steel is used contg. C 0.1-0.2%, Mn 0.8-2.0% and Al 0.03-0.10% and satisfying the ratio of Mn/C<=7. The ratio of Mn/C<=7 results in a stable high Charpy impact value over a wide temp. range and high tensile strength. Accordingly, the steel can be used without being checked over a long term when used as a material for a molten slag pan undergoing sudden heat impacts.
TL;DR: In this paper, the propensity to strain aging of six HSLA steels with ferrite-pearlite and with acicular ferrite microstructures was investigated by tensile and Charpy impact tests.
Abstract: The propensity to strain aging of six HSLA steels with ferrite-pearlite and with acicular ferrite microstructures was investigated by tensile and Charpy impact tests. Tensile prestraining was either at 1.3 pct or 4 pct. The subsequent aging treatments were at temperatures to simulate natural aging, accelerated aging, stress relieving and coating. While all steels were more or less responsive to strain aging as observed by other investigators, the superposition of strain aging cycles caused a severe reduction of uniform elongation and thus, of the formability of all but one of the steels.
01 Jan 1980
TL;DR: In this paper, the impact transition behavior of commercial heats of three low interstitial vacuum induction melted high-chromium ferritic stainless steels was studied as a function of gage.
Abstract: Impact transition behavior of commercial heats of three low interstitial vacuum induction melted high-chromium ferritic stainless steels was studied as a function of gage. A 50 percent shear fracture (FATT 5 0 ) (fracture appearance transition temperature) of Charpy V-notch impact specimens was used as the transition criterion. E-BRITE alloy, a 26Cr-1Mo alloy, was studied as formerly melted using electron beam refining and as currently melted by vacuum induction melting. With either melting, E-BRITE shows substantially lower impact transition at a given gage than a titanium-stabilized 26Cr-1Mo alloy made to conventional interstitial levels. Gage was observed to affect impact transition, with light gages showing lower FATT 5 0 . Slow cooling from anneal is observed to substantially increase FATT 5 0 in comparison with water quenching. This effect is also seen in the heat-affected zone of welds. Using proper shielding and preparation, however, weld metal and base metal away from the weld show similar transition temperatures. The other two alloys studied are high-purity materials containing 29Cr-4Mo and 29Cr-4Mo-2Ni, respectively. These are similar to E-BRITE alloy in impact behavior with the exceptions (1) that 2 percent nickel can lower water-quenched FATT 5 0 , and (2) that these alloys are sensitive to precipitation of σ and Χ phases. Full-size (10 mm) impact specimens of each alloy can show FATT 5 0 below room temperature if satisfactorily heat-treated.