Thermomechanical fatigue of particulate-reinforced aluminum 2xxx-T4

Thermomechanical fatigue (TMF) and isothermal fatigue of unreinforced and SiC_p-reinforced aluminum 2xxx-T4 alloy were examined. Thermomechanical fatigue experiments were conducted underT _min = 100 °C,T _max = 300 °C andT _min = 100 °C,T _max = 200 °C conditions, and isothermal experiments were conducted at 200 °C and 300 °C. Based on stress range, substantial improvements in fatigue life were observed with reinforcement under both isothermal and thermomechanical loading conditions. Based on strain range, the TMF lives of the reinforced material increased in out-of-phase (OP) loading and remained unchanged in in-phase (IP) loading. A decrease in isothermal fatigue lives of the reinforced material compared to those of unreinforced material was observed in both 3 × 10⁻³ s⁻¹ and 3 × 10⁻⁵ s⁻¹ experiments at 200 °C and in 3 × 10⁻³ s⁻¹ experiments at 300 °C. Crack growth mechanism maps were constructed to identify crack growth behavior of the unreinforced and the reinforced materials. The TMF OP conditions were more favorable to transgranular cracking. Mixed (transgranular and intergranular) crack growth occurred in TMF IP experiments. Evidence of void formation at grain boundaries, crack deflection due to particles, and oxide penetration at the crack tips is demonstrated using scanning electron microscopy (SEM) and Auger spectroscopy analysis.     

High Cycle Fatigue of (Fe,Ni, Co)3V type alloys

High cycle fatigue tests in vacuum have been performed on ordered (Fe, Co, Ni)₃V alloys between 25 °C and 850 °C. Heat-to-heat variations in fatigue properties of a Co-16.5 wtpct Fe-25 pct alloy, LRO-1, appeared to be due to differing quantities of grain boundary precipitates. Modification of this alloy with 0.4 pct Ti, to produce an alloy designated LRO-23, reduced the density of grain boundary precipitates and increased ductility, resulting in superior fatigue strength at high temperatures. The fatigue lives of LRO-1 and LRO-23 decreased rapidly above 650 °C, and increased intergranular failure was noted. The fatigue resistance of a cobalt-free alloy, Fe-29 pct Ni-22 pct V-0.4 pct Ti (LRO-37), was examined at 25 °C, 400 °C, and 600 °C; there was little evidence for intergranular fracture at any of these temperatures. Fatigue behavior of the LRO alloys is compared to that of conventional high temperature alloys.     

Thermomechanical Fatigue Behavior of the Intermetallic <Emphasis Type="Italic">γ</Emphasis>-TiAl Alloy TNB-V5 with Different Microstructures

The cyclic deformation and fatigue behavior of the γ-TiAl alloy TNB-V5 is evaluated under thermomechanical load for three different microstructures. For this purpose, strain-controlled thermomechanical fatigue (TMF) tests were carried out with different temperature-strain cycles, different temperature ranges from 400 °C to 800 °C (673 K to 1073 K), and with two different strain ranges to set a fatigue-life relation. Cyclic deformation curves, stress-strain hysteresis loops, and fatigue lives of the tests are presented. The microstructures near-gamma (NG) and duplex (DP) show comparable fatigue lives under all test parameters. The microstructure fully-lamellar (FL) offers longer fatigue lives at the same loading conditions. For a general life prediction, the damage parameter of Smith, Watson, and Topper, P _SWT vs fatigue life, is well suitable, if the testing and the application temperature ranges, respectively, include temperatures above the ductile-brittle transition (approximately 750 °C). In the completely brittle material behavior regime the quality of the lifetime prediction is unacceptable. The damage parameter P _HL by Haibach and Lehrke shows a comparable correlation to the fatigue life as P _SWT. The results are discussed with microstructural investigations.     

Comparison of orthorhombic and alpha-two titanium aluminides as matrices for continuous SiC-reinforced composites

The attributes of an orthorhombic Ti aluminide alloy, Ti-21Al-22Nb (at. pct), and an alpha-two Ti aluminide alloy, Ti-24Al-11Nb (at. pct), for use as a matrix with continuous SiC (SCS-6) fiber reinforcement have been compared. Foil-fiber-foil processing was used to produce both unreinforced (“neat”) and unidirectional “SCS-6” reinforced panels. Microstructure of the Ti-24A1-11Nb matrix consisted of ordered Ti₃Al (α ₂) + disordered beta(β), while the Ti-21 Al-22Nb matrix contained three phases: α₂, ordered beta (β ₀), and ordered orthorhombic(O). Fiber/ matrix interface reaction zone growth kinetics at 982 °C were examined for each composite system. Although both systems exhibited similar interface reaction products(i.e., mixed Ti carbides, silicides, and Ti-Al carbides), growth kinetics in theα ₂ +β matrix composite were much more rapid than in theO +β ₀ +α ₂ matrix composite. Additionally, interfacial reaction in theα ₂ +β} composite resulted in a relatively large brittle matrix zone, depleted of beta phase, which was not present in theO +β ₀+α ₂ matrix composite. Mechanical property measurements included room and elevated temperature tensile, thermal stability, thermal fatigue, thermo-mechanical fatigue (TMF), and creep. The three-phase orthorhombic-based alloy outperformed the α₂+β alloy in all of these mechanical behavioral areas, on both an absolute and a specific(i.e., density corrected) basis.     

Composite materials with an intermetallic matrix based on nickel and titanium monoaluminides hardened by oxide particles or fibers

Hardening phase/intermetallic matrix pairs are chosen for composite materials (CMs) intended for long-term high-temperature operation. These materials must have high and stable mechanical properties during a long time at high temperatures and loads. The compatibility of the physicochemical and mechanical properties of CM components is estimated to choose hardening phase/intermetallic matrix pairs in which the matrix is represented by an alloy based on NiAl or TiAl monoaluminide and the hardening phase is a refractory thermodynamically stable oxide of a Group III transition metal M ₂O₃. The following two schemes are used to perform hardening of a CM with a matrix consisting of a TiAl or NiAl alloy by the most thermodynamically stable interstitial phases, i.e., refractory oxides, at temperatures higher than the operating temperature (T _op) of the IMM. The first scheme consists in creating Al₂O₃/TiAl CMs hardened by continuous single-crystal sapphire fibers using the impregnation of a bundle of single-crystal fibers with a matrix melt followed by directional solidification. The TiAl-based matrix in these CMs serves as a binder connecting oxide phase fibers and preventing them from fracture due to high adhesion forces between oxide fibers and the matrix and a high fiber/matrix interface strength. In the second scheme, Y₂O₃/NiAl CMs are produced by powder metallurgy methods, which include severe deformation by extrusion accompanied by the formation of deformation texture and subsequent recrystallization annealing. In these CMs, disperse refractory oxide particles stabilize grain boundaries in a recrystallized matrix material and lead to the formation of directional structures with coarse elongated grains and a low fraction of transverse boundaries. Al₂O₃/TiAl CMs containing 20–25 vol % hardening single-crystal sapphire Al₂O₃ fibers can operate at temperatures of 1000–1050°C (∼0.7T _m of matrix), which is 250–300°C higher than the maximum values of T _op of a TiAl-based matrix and 400-450°C higher than the maximum values of T _op of a Ti-based matrix. An Y₂O₃/NiAl composite with a directionally recrystallized structure of a NiAl-based matrix hardened by 2.5 vol % Y{ia2}O₃ particles can be recommended for operation at temperatures of 1400–1500°C ((0.8–0.9)T _m of matrix), which are higher by 100–400°C than not only T _op but also T _m of Ni superalloys.     

The influence of ageing on fatigue crack growth in SiC-particulate reinforced 8090

A study of the influence of SiC-particulate reinforcement on ageing and subsequent fatigue crack growth resistance in a powder metallurgy 8090 aluminium alloy-SiC composite has been made. Macroscopic hardness measurements revealed that ageing at 170°C in the composite is accelerated with respect to the unreinforced alloy, though TEM studies indicate that this is not due to the enhanced precipitation of S'. Fatigue crack growth rates in the naturally aged condition of the composite and unreinforced matrix are similar at low to medium values of δK, but diverge above ≈ 8 MPa√m owing to the lower fracture toughness of the composite. As a result of the presence of the reinforcement, planar slip in the composite is suppressed and facetted crack growth is not observed. Ageing at or above 170°C has a deleterious effect on fatigue crack growth. Increased ageing time decreases the roughness of the fracture path at higher growth rates. These effect are though to be due to microstructural changes occurring at or near to the SiC/matrix interfaces, providing sites for static mode failure mechanisms to operate. This suggestion is supported by the observation that as δK increases, crack growth rates become K_max dependent, implying the crack growth rate is strongly influenced by static modes.     

The influence of growth rate and temperature on high cycle fatigue of Al-Al3Ni

High-cycle fatigue tests have been conducted on specimens of an Al-Al₃Ni eutectic alloy, unidirectionally solidified at selected rates from 1.39 × 10^-4 cm/s to 0.3 cm/s. Tests were conducted in air at 298, 458 and 683 K. Room temperature fatigue lives were independent of growth rate at low solidification rates (1.39 × 10^-4•8.33 × 10^-3 cm/s, but were markedly improved in samples grown at 0.3 cm/s. Materials grown at 8.33 × 10^-3 cm/s exhibited fatigue lives similar to those of the lower growth rates, despite gross misalignment due to cellular growth. At 0.5T _m (458 K) and 0.75T _m (683 K), the fatigue lives of the material grown at low solidification rates were dependent on growth rate. The dependence of fatigue life on growth rate at elevated temperatures appears to be due primarily to differences in cyclic creep rates as a result of varying interfiber spacings. Crack initiation and propagation mechanisms were established by metallographic and fractographic examination. Dislocation substructure-fiber interactions were studied by transmission electron microscopy.     

Thermomechanical fatigue behavior of the third-generation,single-crystal superalloy TMS-75: Deformation structure

The deformation structure after the out-of-phase thermomechanical fatigue (OP TMF) of the single-crystal (SC), Ni-based superalloy TMS-75 has been studied. Mechanical experiments were performed at temperatures between 400 °C and 900 °C under different total strain ranges with varying hold times in the compression stage. The lives of TMF for samples with hold times of 10 and 60 minutes dropped drastically by one order of magnitude as compared with those without it. Different structures developed during TMF were correlated to the difference in mechanical behavior for the two cases. The dislocations in the γ phase and the stacking faults (SFs) in the γ′ phase were quantitatively analyzed by transmission electron microscopy (TEM). This work verified that shearing of the γ′ precipitates occurred with a single-dislocation mechanism rather than a dislocation-reaction mechanism. The implications of this work on the design of superalloys are presented.     

The low-cycle fatigue and fatigue-crack-growth behavior of HAYNES® HR-120 alloy

The low-cycle fatigue and fatigue-crack-growth behavior of the HAYNES HR-120 alloy was investigated over the temperature range of 24°C to 980°C in laboratory air. The result showed that increasing the temperature usually led to a substantial decrease in the low-cycle fatigue life. The reduction of fatigue life could be attributed to oxidation and dynamic strain-aging (DSA) processes. The strain vs fatigue-life data obtained at different temperatures were analyzed. It was also found that the fatigue-crack-growth rate per cycle generally increased with increasing temperature and R ratio (R=σ _min/σ _max, where σ _min and σ _max are the applied minimum and maximum stresses, respectively). The relationship between the stress-intensity-factor range and fatigue-crack-growth rate was determined. Scanning-electron-microscopy (SEM) examinations of the fracture surfaces revealed that the fatigue cracks initiated and propagated predominantly in a transgranular mode.     

Thermomechanical deformation modeling of Al2xxxT4/SiCp composites

A constitutive model for metal matrix composites is developed and its capabilities for predicting cyclic isothermal and cyclic thermomechanical behavior are demonstrated. The silicon carbide particulate reinforced Al2xxxT4 alloy was studied experimentally and theoretically with the model. Cyclic stress-strain behavior of 15 and 20% reinforced silicon carbide particulate reinforced Al2xxx-T4 were successfully predicted at temperatures of 20, 200 and 300°C at strain rates between 3 × 10⁻⁵s⁻¹ and 3 × 10⁻³s⁻¹. The themomechanical stress-strain behaviors (T_min = 100°C, T_max = 200, 300°C) were studied experimentally and the results were closely predicted when temperature-strain phasing was in-phase and out-of-phase. This study clarifies the influence of mechanical property mismatch in the elastic and in the inelastic ranges vs the thermal property mismatch on composite and the matrix behaviors. The transverse and hydrostatic stresses in the matrix, developed during cyclic loading, are reported for both isothermal and thermomechanical loading conditions.     

The effect of tempering temperature on near- threshold fatigue crack behavior in quenched and tempered 4140 steel

Fatigue crack growth in compact tension samples of high purity 4140 steel quenched and tempered to various strength levels was investigated. Tempering temperatures of 200, 400, 550, and 700 °C produced yield strengths from 1600 to 875 MPa, respectively. Crack propagation and crack closure were monitored inK-decreasing tests performed underR = 0.05 loading conditions in laboratory air. Results indicated that as the yield strength increased the crack growth rate increased at a given ΔK and ΔK_th decreased. Threshold values varied from 2.8 MPa m^1/2 (200 °C temper) to 9.5 MPa m_1/2 (700 °C temper). Cracks in the 200 °C tempered samples grew by an intergranular mechanism following prior austenite grain boundaries probably caused by hydrogen embrittlement or tempered martensite embrittlement. Tempering above 200 °C produced transgranular fatigue crack growth. The level of crack closure increased with tempering temperature and with crack propagation in a given tempered condition. Crack closure was caused by a combination of plasticity-induced and oxide-induced mechanisms. The use of an effective stress intensity range based on crack closure consolidated the fatigue crack growth curves and the threshold values for all tempering temperatures except 200 °C. Formerly Graduate Research Assistant, Department of Materials Science and Engineering, Stanford University, Stanford, CA. Formerly Professor, Department of Materials Science and Engineering, Stanford University, Stanford, CA.     

Localized corrosion susceptibility of Al-Li-Cu-Mg-Zn alloy AF/C458 due to interrupted quenching from solutionizing temperature

Isothermal time-temperature-localized corrosion-behavior curves were determined for the Al-1.8Li-2.70Cu-0.6Mg-0.3Zn alloy AF/C458, to understand the effect of slow or delayed quenching on localized corrosion susceptibility. Alloy samples were subject to a series of systematic interrupted quenching experiments conducted at temperatures ranging from 480 °C to 230 °C for times ranging from 5 to 1000 seconds. Individual samples were then exposed to an oxidizing aqueous chloride solution consisting of 57 g/L NaCl plus 10 mL/L H₂O₂ to induce localized attack. The localized corrosion mode was characterized by optical microscopy. Additionally, the microstructure of selected samples was characterized by transmission electron microscopy (TEM) to relate the corrosion mode and morphology to microstructural features. Results showed that only pitting attack was exhibited by samples subjected to isothermal treatment at temperatures greater than 430 °C. At temperatures ranging from 280 °C to 430 °C, isothermal treatment tended to induce susceptibility to intergranular attack (IGA) and intersubgranular attack (ISGA) for all treatment times investigated. For isothermal treatments at temperatures lower than 280 °C, only pitting was observed for treatment times less than about 30 seconds, while IGA and ISGA were observed for longer treatment times. Comparisons showed that the time-temperature domains for IGA and ISGA were virtually coincident. Based on this finding and the results from TEM characterization, IGA and ISGA appear to be related to the precipitation of a Zn-modified T ₁ (Al₂(Cu,Zn)Li) precipitate, which can occur both on low-angle and high-angle grain boundaries in this alloy. When the alloy is resistant to IGA and ISGA, the grain boundaries are decorated by θ′ (Al₂Cu), and T _B (Al₇Cu₄Li) phase particles, or subgrain boundaries are populated by a comparatively low density of T ₁ precipitates. It is, therefore, speculated that θ′ and T _B are more corrosion-resistant precipitate phases than T ₁, and that a critical concentration of boundary T ₁ must exist for IGA or ISGA to occur.     

The Effect of Thermomechanical Processing on the Tensile, Fatigue, and Creep Behavior of Magnesium Alloy AM60

Tensile, fatigue, fracture toughness, and creep experiments were performed on a commercially available magnesium-aluminum alloy (AM60) after three processing treatments: (1) as-THIXOMOLDED (as-molded), (2) THIXOMOLDED then thermomechanically processed (TTMP), and (3) THIXOMOLDED then TTMP then annealed (annealed). The TTMP procedure resulted in a significantly reduced grain size and a tensile yield strength greater than twice that of the as-molded material without a debit in elongation to failure (ε _f ). The as-molded material exhibited the lowest strength, while the annealed material exhibited an intermediate strength but the highest ε _f (>1 pct). The TTMP and annealed materials exhibited fracture toughness values almost twice that of the as-molded material. The as-molded material exhibited the lowest fatigue threshold values and the lowest fatigue resistance. The annealed material exhibited the greatest fatigue resistance, and this was suggested to be related to its balance of tensile strength and ductility. The fatigue lives of each material were similar at both room temperature (RT) and 423 K (150 °C). The tensile-creep behavior was evaluated for applied stresses ranging between 20 and 75 MPa and temperatures between 373 and 473 K (100 and 200 °C). During both the fatigue and creep experiments, cracking preferentially occurred at grain boundaries. Overall, the results indicate that thermomechanical processing of AM60 dramatically improves the tensile, fracture toughness, and fatigue behavior, making this alloy attractive for structural applications. The reduced creep resistance after thermomechanical processing offers an opportunity for further research and development.     

On the fracture and fatigue properties of Mo-Mo<Subscript>3</Subscript>Si-Mo<Subscript>5</Subscript>SiB<Subscript>2</Subscript> refractory intermetallic alloys at ambient to elevated temperatures (25 °C to 1300 °C)

The need for structural materials with high-temperature strength and oxidation resistance coupled with adequate lower-temperature toughness for potential use at temperatures above ∼1000 °C has remained a persistent challenge in materials science. In this work, one promising class of intermetallic alloys is examined, namely, boron-containing molybdenum silicides, with compositions in the range Mo (bal), 12 to 17 at. pct Si, 8.5 at. pct B, processed using both ingot (I/M) and powder (P/M) metallurgy methods. Specifically, the oxidation (“pesting”), fracture toughness, and fatigue-crack propagation resistance of four such alloys, which consisted of ∼21 to 38 vol. pct α-Mo phase in an intermetallic matrix of Mo₃Si and Mo₅SiB₂ (T₂), were characterized at temperatures between 25 °C and 1300 °C. The boron additions were found to confer improved “pest” resistance (at 400 °C to 900 °C) as compared to unmodified molybdenum silicides, such as Mo₅Si₃. Moreover, although the fracture and fatigue properties of the finer-scale P/M alloys were only marginally better than those of MoSi₂, for the I/M processed microstructures with coarse distributions of the α-Mo phase, fracture toughness properties were far superior, rising from values above 7 MPa √m at ambient temperatures to almost 12 MPa √m at 1300 °C. Similarly, the fatigue-crack propagation resistance was significantly better than that of MoSi₂, with fatigue threshold values roughly 70 pct of the toughness, i.e., rising from over 5 MPa √m at 25 °C to ∼8 MPa √m at 1300 °C. These results, in particular, that the toughness and cyclic crack-growth resistance actually increased with increasing temperature, are discussed in terms of the salient mechanisms of toughening in Mo-Si-B alloys and the specific role of microstructure.     

Microstructural refinement and mechanical properties improvement of elemental powder metallurgy processed Ti-46.6Al-1.4Mn-2Mo alloy by carbon addition

Strengthening of a gamma TiAl alloy was sought by a chemical modification of the composition with carbon. Up to 0.6 at. pct of carbon was added to the Ti-46.6Al-1.4Mn-2Mo alloy processed by elemental powder metallurgy. Carbon addition resulted in considerable microstructural changes such as refinement, by a factor of about 2, of the lamellar microstructure and carbide precipitation. The cause of the lamellar structure refinement is twofold, increased heterogeneous nucleation rate and decreased γ platelet growth rate, the net result of which was a retarded diffusional transformation kinetics of α to α/γ lamellae. As a consequence of the microstructural changes, the high-temperature tensile properties and the creep properties of the alloy were significantly improved. Anomalous hardening was also observed at 800 °C, resulting in a tensile yield strength of 700 MPa. The strengthening effect of carbon was realized by the microstructural refinement and by precipitation hardening of intergranular as well as interlamellar Ti₃AlC. In terms of the tensile properties and the creep properties, the optimum amount of carbon addition was 0.3 at. pct.     

Comparisons of experimental measurements and a theoretical model for specimen self-heating during fatigue of type 316 LN stainless steel

The Type 316 stainless steel is being considered as a candidate target-container material for the spallation neutron source (SNS) being built at the Oak Ridge National Laboratory. Satisfactory behavior under fatigue loading is a requirement for the target container. Stress-controlled fatigue experiments were performed on the 316 stainless steel at 0.2 and 10 Hz with an R ratio of −1, where R=σ _min./σ _max.; σ _min. and σ _max. are the minimum and maximum applied stresses, respectively. At R=−1, a large specimen-temperature increase at 10 Hz was observed, which approached approximately 350 °C at a stress amplitude of 263 MPa, and affected fatigue lives. The specimen temperature at 0.2 Hz was about room temperature. The fatigue lives at 10 Hz were found to be shorter than those at 0.2 Hz. Different specimen temperatures were achieved by varying test frequencies. Significant differences in fatigue lives as a function of test frequency were observed with shorter fatigue lives at higher frequencies. The higher specimen temperature at 10 than at 0.2 Hz reduced the fatigue life at 10 Hz. A model based on the dissipation energy of the specimen during fatigue tests was developed to explain the fatigue-life result and predict the specimen-temperature evolution. The present research is sponsored by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, United States Department of Energy, under Contract No. DE-AC05-00OR22725 with UT-Battelle, LLC.     

Influence of time and temperature dependent processes on strain controlled low cycle fatigue behavior of alloy 617

Strain controlled low cycle fatigue tests have been conducted in air to ascertain the influence of strain rate(ε = 4 × 10^-6'to 4 × 10^-3 s^-1) and temperature(T = 750/850/950 °C) on LCF behavior of Alloy 617. A strain range of 0.6 pct and a symmetrical triangular wave form were employed for all the tests. Crack initiation and propagation modes were studied. Microstructural changes that occurred during fatigue deformation were evaluated and compared with the results obtained on isothermal aging. Deformation and damage mechanisms which influence the endurance have been identified. A reduction in fatigue life was observed with decreasing ε at 850 °C and with increasing temperature at ε = 4 × 10^-5 s^-1. Cyclic stress response varied as a complex function of temperature and strain rate. Fatigue deformation was found to induce cellular precipitation of carbides at 750 and 850 ‡. Dynamic strain aging characterized by serrated flow was observed at 750 °C (ε = 4 × 10^-5 s^-1) and in the tests at higher ε at 850 °C. Strengthening of the matrix due to dynamic strain aging of matrix dislocations by precipitation of M₂₃C₆ carbides led to fracture of grain boundary carbide films formed at 750 °C, producing brittle intergranular crack propagation. At 850 °C transgranular crack propagation was observed at the higher strain rates ε≥4× 10^-4 s^-1. At 850 and 950 °C even at strain rates of 4 × 10^-5 s^-1 or lower, life was not governed by intergranular creep rupture damage mechanisms under the symmetrical, continuous cycling conditions employed. Reduction of endurance at lower strain rates is caused by increased inelastic strain and intergranular crack initiation due to oxidation of surface connected grain boundaries. formerly Guest Scientist at the De-partment for Reactor Materials of the Nuclear Research Centre, Juelich (IRW/KFA),     

On the mechanisms of high-temperature intergranular embrittlements of Ni3Al-Zr Alloys

Recent studies on the room-temperature fracture behavior of Ni₃Al-Zr alloys after preexposure at elevated temperatures show various types of intergranular failure. In the presently studied Ni₇₈Al₂₁Zr₁B_0.2 alloy, a strong intergranular fracture tendency at room temperature has been found after preexposure at 750 °C, which is caused by the grain boundary precipitation in this alloy. After short-term exposure above 1200 °C and bending fracture at room temperature, the alloy also suffers intergranular embrittlement due to grain boundary melting. The intergranular fracture appearance is quite different from that observed in a previous study for a Ni_77.4Al₂₂Zr_0.6B_0.2 alloy after air exposure for 100 hours at 1200 °C. In that case, the intergranular fracture was accompanied by grain boundary diffusion (invasion) and segregation of oxygen. The mechanisms of these types of grain boundary failure are discussed. Formerly Doctoral Candidate, Institute of Materials Science and Engineering, National Taiwan University.     

Creep-fatigue life prediction of in situ composite solders

Eutectic tin-lead solder alloys subjected to cyclic loading at room temperature experience creep-fatigue interactions due to high homologous temperature. Intermetallic reinforcements of Ni₃Sn₄ and Cu₆Sn₅ are incorporated into eutectic tin-lead alloy by rapid solidification processes to formin situ composite solders. In this study, thein situ composite solders were subjected to combined creep and fatigue deformation at room temperature. Under cyclic deformation, the dominant damage mechanism ofin situ composite solders is proposed to be growth of cavities. A constrained cavity growth model is applied to predict creep-fatigue life by taking into account the tensile loading component as well as the compressive loading component when reversed processes can occur. An algorithm to calculate cavity growth in each fatigue cycle is used to predict the number of fatigue cycles to failure, based on a critical cavity size of failure. Calculated lives are compared to experimental data under several fatigue histories, which include fully reversed stress-controlled fatigue, zero-tension stress-controlled fatigue, stress-controlled fatigue with tension hold time, fully reversed strain-controlled fatigue, and zero-tension straincontrolled fatigue. The model predicts the creep-fatigue lives within a factor of 2 with the incorporation of an appropriate compressive healing factor in most cases. Discrepancy between calculated lives and experimental results is discussed. This article is based on a presentation made in the symposium entitled “Creep and Fatigue in Metal Matrix Composites” at the 1994 TMS/ASM Spring meeting, held February 28–March 3, 1994, in San Francisco, California, under the auspices of the joint TMS-SMD/ASM-MSD Composite Materials Committee.