Aços microligados pertencem à classe dos aços ARBL contendo baixa ou média quantidade de carbono e pequena adição de elementos de liga tais como Mn, Nb, Mo, V e Ti. A variedade microestrutural desses aços pode ser obtida dependendo da temperatura de conformação, taxa de resfriamento e composição química. Os tratamentos intercríticos e isotérmicos produzem microestruturas multifásicas com diferentes quantidades de ferrita, martensita, bainita e austenita retida. A presença de diferentes fases nestes materiais, com morfologias distintas, pode afetar de modo significativo seu comportamento mecânico, afetando, por exemplo, o fechamento da trinca e resultando em mudanças na taxa de crescimento da mesma. O objetivo deste trabalho é avaliar as propriedades de tração e a resistência ao crescimento da trinca por fadiga de um aço microligado RD 480 com 0.08%C-1, 5%Mn (p), correlacionando-as com suas características microestruturais. Esse aço, desenvolvido recentemente pela CSN (Companhia Siderúrgica Nacional), é considerado promissor como alternativa para substituir o aço de baixo carbono utilizado em componentes de rodas na indústria automotiva. Distintas condições microestruturais foram obtidas por meio de tratamentos térmicos seguidos de resfriamento em água. As condições de tratamento intercrítico e têmpera simples foram escolhidas para se avaliar a resistência à propagação da trinca por fadiga. Os resultados dos ensaios foram sintetizados em termos da taxa de crescimento da trinca (da/dN) versus a variação do Fator Intensidade de Tensão (_K) no ciclo de carregamento. Para descrever o comportamento das trincas foram utilizados dois modelos: a equação convencional de Paris e um novo modelo exponencial que mostra o comportamento não linear das curvas de fadiga. Os resultados mostraram que uma microestrutura combinando ferrita de aspecto acicular e fases duras (martensita/bainita) resultou em menores taxas de crescimento da trinca. No entanto, a melhor combinação entre as propriedades de tração (limite de escoamento, resistência e ductilidade) e fadiga foi obtida com uma microestrura bifásica contendo martensita dispersa em uma matriz ferrítica. Observou-se uma transição nas curvas de crescimento da trinca para todas as condições tratadas termicamente e, por conta disto, as curvas das condições microestruturais bifásicas e multifásicas foram melhores modeladas quando divididas em duas regiões. As superfícies de fratura dessas amostras, bem como o caminho percorrido pela trinca, foram analisados via MEV e MO. / Microalloyed steels are a class of HSLA steels with low or medium carbon content and small additions of alloy elements such as Mn, Nb, Mo, V and Ti. A variety of microstructures in microalloyed steels can be obtained depending on the deformation temperature, cooling rate and chemical composition. Heat treatments and isothermal transformation on these materials, with various temperatures and holding times, produce multiphase microstructures with different amounts of ferrite, martensite, bainite and retained austenite. These different phases, with distinct morphologies, are determinant of the mechanical behavior of the steel and can, for instance, affect crack closure or promote crack shielding, thus resulting in changes on its propagation rate under cyclic loading. The aim of this study is to evaluate the tensile properties and resistance to fatigue crack growth in a microalloyed steel RD 480 with 0.08%C-1, 5% Mn (wt), correlating with their microstructural characteristics. This steel, recently developed by CSN (Companhia Siderurgica Nacional), is being considered as a promising alternative to replace low carbon steel in wheel components for the automotive industry. Distinct microstructural conditions were obtained by means of heat treatments followed by water quench. The intercritical treatment and quenching conditions were chosen to evaluate the strength to crack propagation. The crack propagation test results were summarized in terms of FCG rate (da/dN) versus stress intensity factor range (?K) curves. In order to describe the FCG behavior, two models were tested: the conventional Paris equation and a new exponential equation developed for materials showing non-linear FCG behavior. The results showed that a microstructure combining aspect acicular ferrite and hard phases (martensite / bainite) resulted in lower rates of crack growth. However, the best combination between the tensile properties (yield stress, tensile strength and ductility) and fatigue was obtained with a dual phase steel microstructure containing martensite dispersed in a ferrite matrix. It was observed a transition in the crack growth curves for all heat treated conditions, so the curves of the dual and multiphase microstructural conditions were better modeled by dividing them in two regions. The fracture planes of the fatigued specimens, as well as the crack path, were examined using a scanning electron microscope (SEM) and optical micrography (OM).

Neste trabalho foi avaliada a influência das condições de processamento (pouring temperature and de vazamento e condições de isolamento térmico dos moldes cerâmicos) na formação de trincas nas palhetas de turbinas policristalinas, a base da superliga B1914, produzidas por microfusão. E devido à falta de informações sobre a superliga B1914 foram levantadas informações sobre o equilíbrio de fases (THERMOCALC) e foi realizada a caracterização microestrutural e mecânica deste material desta liga no estado bruto e tratada termicamente. Todas as palhetas vazadas a 1570, 1520 e 1470 °C em moldes sem isolamento e com isolamento parcial apresentaram trincas e outros defeitos de solidificação. Já as palhetas vazadas em moldes totalmente isolados estavam livres das trincas. No entanto foram identificados aglomerados de microporos na raíz de todas as palhetas. Os resultados de simulação de fração de fases mostraram que o equilíbrio de fases da superliga B1914 é constituído majoritariamente pelas fases γ e γ\' e pelas fases minoritárias MB2, M3B2 e sigma. A caracterização microestrutural da superliga B1914 confirmou os resultados de simulação e foram identificadas as fases gama (&#947) - dendritas e os precipitados da fase gama linha (&#947\') - no interior das dendritas e na região interdendrítica. As fases M3B2 e eram os microconstituintes do eutético. Os resultados de DTA e Scheil mostraram que o processo de solidificação, da superliga B1914, ocorreu fora de equilíbrio. Nos resultados obtidos a partir dos tratamentos térmicos, ficaram evidentes as dificuldades encontradas para solubilização das placas da fase &#947\'. A integridade estrutural dos corpos-de-prova foi comprometida pela presença de defeitos de solidificação (vazios). Tanto que os valores de LR e r obtidos nos ensaios estão muito abaixo dos valores encontrados na literatura. / This study was evaluated the influence of processing conditions (temperatures of casting conditions and thermal insulation of ceramic shells) in crack formation of equiaxed B1914 turbine blades produced by investment casting. Due to lack of information about B1914 alloy was performed microstructural and mechanical characterization of this alloy material in the raw state and treated. In shells uninsulated and partly insulated, after pouring was observed casting solidification defects. However the shells in a fully insulated were not observed casting crack formation. However were identified clusters of micropores in the root of all blades. The results of simulation phase fraction showed that the balance of phases in B1914 alloy is made mostly by γ and γ\' phases and the minority phases: MB2, M3B2 and sigma. The microstructural characterization of B1914 alloy confirmed the results of simulation and were identified: gamma (γ) - dendrites and gamma prime (γ\') - inside the dendrites and interdendritic regions. The M3B2 was found in eutectic. The results of DTA and Scheil showed that the process of solidification occurred in non-equilibrium. The results obtained from the thermal treatments showed difficulties to solubilize γ\' phase. The structural integrity of samples was compromised by the presence of solidification defects (pores). Both values of LR and εr obtained in the tests are much below the values found in literature.

Atualmente, há a necessidade de se desenvolver aços com alta resistência à propagação de trincas, especialmente em condições de carregamentos cíclicos, ou seja, resistentes à fadiga, na qual sua aplicabilidade se da em função de suas propriedades mecânicas. No presente trabalho estudou-se o efeito do preaquecimento na zona afetada pelo calor do aço AISI/SAE 4130 com composição química modificada, com altos teores de Mo, comparando as propriedades mecânicas e microestruturais nas condições como soldada, tratada termicamente e aplicando a técnica de Metodologia do Preaquecimento Combinado (MPC) com otimização de ciclos térmicos através da combinação do preaquecimento entre o 1º e 3º passe da 1º e 2º camada, respectivamente. A fim de avaliar as propriedades mecânicas, foram realizados ensaios de microdureza, mapeamento de dureza e ensaio de tenacidade ao impacto charpy. Para análise microestrutural, foi realizado microscopia ótica e microscópio eletrônico de varredura (MEV) para analisar as regiões de grãos grosseiros, fino e as intersecções entre as regiões da Zona Afetada pelo Calor (ZAC), quando aplicado o MPC. Como resultado, observa-se que preaquecimento é uma forma efetiva de redução de dureza, chegando a uma redução máxima de 71 HV0,1, quando comparado às temperaturas de preaquecimento entre 150 e 400 ºC. No entanto há um severo efeito deletério na tenacidade, podendo chegar a uma queda de 71% da energia absorvida. O tratamento térmico pós soldagem (TTPS) se mostrou eficiente apenas para amostra soldada com temperaturas de preaquecimento de 150 ºC, para as demais temperaturas não houve benefício, tanto em redução de dureza, quanto na restauração da tenacidade. No entanto, para temperatura de preaquecimento de 230 ºC também foi observado o acréscimo de dureza após o TTPS devido ao efeito de endurecimento secundário por precipitação de carbonetos metálicos (MC). A técnica MPC se mostrou muito eficiente em redução da dureza e restauração da tenacidade, e este fenômeno está associado à capacidade de solubilizar os carbonetos que precipitam durante a soldagem, fenômeno que não ocorre com a aplicação do TTPS. / Currently, it is necessary to develop materials with high resistance to crack propagation, especially under conditions of cyclic loading condition such as fatigue resistant, in which its applicability is due to its mechanical properties. In the present work the effect of preheating in the heat-affected zone of the AISI / SAE 4130 steel with modified chemical composition (High Mo) was compared, regarding its mechanical and microstructural properties of each welding condition, As weld, post weld heat treated and applying the Methodology of combined preheating (MCP) with optimization of thermal cycles by combining the preheating between the 1st pass of 1st layer and the 3rd pass of 2nd layer. In order to evaluate the mechanical properties, microhardness tests, hardness mapping and charpy V notch tests were performed. For microstructural analysis, optical and scanning electron microscopy (SEM) were used to analyze the coarse grained regions and the intersections between the Heat Affected Zones (HAZ) regions, when applied to the MPC. As a result, it is observed that preheating is an effective form of reduction of hardness, reaching a maximum reduction of 71 HV0,1, when compared to the preheating temperatures between 150 and 400ºC, however there is a severe deleterious effect in the toughness, dropping up to 71% of the absorbed energy. The post weld heat treatment (PWHT) is efficient only for welded sample with preheating temperatures of 150 ºC, for the other temperatures there was no benefit, either in reduction of hardness or restoration of toughness. However, for the preheating temperature of 230 °C it was observed the increase of hardness after the PWHT due to the effect of secondary hardening by precipitation of metal carbides (MC). The MPC technique proved to be very efficient in decreasing hardness and restoring toughness, and this phenomenon is associated with the ability to solubilize the carbides that precipitate during welding, which is not observed while PWHT is applied.

Bakgrunden till detta examensarbete var att Qumex Materialteknik vid ett flertal tillfällen konstaterat att material av typen SS 0725 har uppvisat bristfälliga härdresultat. Materialet, som är relativt nytt på marknaden, är ett gjutjärn av typen segjärn och utmärker sig gentemot andra segjärn på grund av sitt höga innehåll av kisel. Då segjärn enligt den nu gällande EN-standarden klassificeras efter sina mekaniska egenskaper uppstår ett problem gällande SS 0725. Materialet uppfyller de krav som är ställda för EN-GJS-500-7 och hamnar därmed under samma materialbeteckning som ett segjärn med betydligt lägre kiselhalt. Att två material med olika kemisk sammansättning hamnar under samma beteckning kan innebära problem. Syftet med denna rapport är att fastslå vilken påverkan den höga kiselhalten har på materialet vid värmebehandling av typen släckhärdning med efterföljande anlöpning. I försöken ingick fyra material. Det som skiljde materialen åt var halterna av koppar och kisel. De härdades vid tre olika temperaturer och under tre olika tider för att sedan släckas i olja. Målet med släckhärdningen var att materialen skulle få en helt martensitisk struktur vilket då klassades som ett bra härdresultat. Resultatet utvärderades sedan genom optisk mikroskopi och hårdhetsmätningar. En undersökning av materialens fasomvandlingstemperaturer genomfördes med hjälp av Differential Scanning Calorimetry. Resultatet visar att kiselhalten har stor påverkan på den temperatur som krävs för att erhålla ett bra härdresultat. För material med låg kiselhalt uppnåddes fullständig martensitbildning efter släckhärdning från 840°C. För material med hög kiselhalt uppnåddes liknande strukturella och hårdhetsmässiga resultat först vid en så hög temperatur som 900°C och behandlingstider längre än 1 h. Den relativa skillnad som uppmättes i fasomvandlingstemperatur med hjälp av Differential Scanning Calorimetry mellan högkiselmaterial och lågkiselmaterial var 45°C. Detta resultat kombinerat med analyserna av härdprocesserna visar att det krävs kraftigt ökad temperatur vid värmebehandling av högkiselmaterialet SS 0725. / The background to this thesis was that Qumex Materialteknik at several occasions had received material of type SS 0725 that had shown deficient heat treatment results. The material, which is relatively new, is a cast iron of type ductile iron and differ against other ductile irons because of its high silicon content. According to EN standard ductile irons are classified by their mechanical properties. A problem then occurs with the new material SS 0725 because of this. The material fulfils the requirements for EN-GJS-500-7 and is therefore in the same classification as a ductile iron with much lower silicon content. Two materials having major differences in chemical composition ending up in the same classification can be problematic. The purpose of this report is to determine impact of high silicon content in ductile iron when heat treated and quench hardened. The experiment included four materials, and the major difference between the materials were their content of copper and silicon. The heat treatment process was performed at three different temperatures and three different treatment times. Afterwards the samples were quenched in oil. The ambition of the quench hardening was to obtain a material structure of 100% martensite. By optical microscopy and hardness measurements the results then were evaluated. An investigation of the phase transformation temperature in the materials was made by using Differential Scanning Calorimetry. The results show that the amount of silicon content has great influence on the temperature for receiving good hardening results. To achieve 100% martensite after quench hardening in materials with low silicon content the temperature needs to be over 840°C. For material with high level of silicon content the temperature for achieving 100% martensite needs to be 900°C and the treatment time should be over 1 h. The relative difference in phase transformation temperature was measured using Differential Scanning Calorimetry. The results of the measurements between the materials with high silicon content and materials with low silicon content was 45°C. This result combined with the analysis of the heat treatment process shows that a major increase of the temperature is needed to heat treat SS 0725.

The metallurgical processes and the products developed from these processes have been the cornerstone on which our civilizations have developed and flourished. Many of the new materials that have been developed over centuries were often the result of serendipitous occurrences. Because of the importance of new materials to the improvement of society, it is necessary to accelerate the way in which new alloys and processes are designed, developed and implemented. Over the last two decades the computational side of materials science has thrived as a result of bigger and faster computers. However, the application of new computational methods to the development of new materials and structures is still in the early stages primarily because of the complexity of most metallurgical processes. One such process is the decarburization of steel. Because of the importance of the microstructure on the mechanical properties, changes in the near surface properties are affected by the loss of carbon in the alloy. The topics investigated in this thesis include a variety of alloys and microstructures that are considered to be important in the development of a unique structure necessary for a more efficient method of recovering natural gas and oil from underground reserves as well as structures for energy absorbing systems. Since both the material application and the structure are new, this research represents an ideal opportunity to combine processing, properties, microstructure and computations to accelerate the development of these new structures. Compared to other commercially available proppants which tend to fail in demanding environments, the thin-walled hollow metal proppants are regarded more promising due to the low density and high mechanical strength. The energy-absorbing composite material manufactured by embedding said spheres in the Mg/Al matrix material is optimized by improving sphere and matrix properties at each step in the process. Ultimately the mechanical strength, fracture toughness, and energy absorption are expected to achieve a factor of 2-5 higher than previously reported. Modeling makes it economically practical to assess the targeted materials' overall properties, behaviors and the mechanical responses in conjunction with stress environment, material properties, material dimensions among other variables, before a structure is built. Additionally, more advanced modeling can enable the quantitative descriptions of more complex metallurgical phenomena such as the effects of impurity elements and deformation under complex loading conditions.

High strength secondary hardening lath martensitic steel is a strong candidate for high performance and reliable transmission systems in aircraft and automotives. The fatigue resistance of this material depends both on intrinsic microstructure attributes, such as fine scale (M2C) precipitates, and extrinsic attributes such as nonmetallic primary inclusions. Additionally, the aforementioned attributes are affected by processing history. The objective of this research is to develop a computational framework to quantify the influence of both extrinsic (primary inclusions and residual stresses) and intrinsic (martensite laths and carbides) microstructure attributes on fatigue crack formation and the early stage of microstructurally small crack (MSC) growth that dominate high cycle fatigue (HCF) lifetime. To model the fatigue response at various microstructure scales, a hierarchical approach is adopted. A simplified scheme is developed to simulate processing effects such as shot peening that is suitable to introduce representative residual stresses prior to conducting fatigue calculations. Novel strategies are developed to couple process route (residual stresses) and microstructure scale response for comprehensive analysis of fatigue potency at critical life-limiting primary inclusions in gear steels. Relevant microstructure-scale response descriptors that permit relative assessment of fatigue resistance are identified. Fatigue crack formation and early growth is highly heterogeneous at the grain scale. Hence, a scheme for physically-based constitutive models that is suitable to investigate crack formation and early growth in martensitic steel is introduced and implemented. An extreme value statistical/probabilistic framework to assess the influence of variability of various microstructure attributes such as size and spatial distribution of primary inclusions on minimum fatigue crack formation life is devised. Understanding is sought regarding the relative role of microstructure attributes in the HCF process, thereby providing a basis to modify process route and/or composition to enhance fatigue resistance. Parametric studies are conducted to assess the effect of hot isostatic pressing and introduction of compliant coatings at debonded inclusion-matrix interface on enhancement of fatigue resistance. A comprehensive set of 3D computational tools and algorithms for hierarchical microstructure-sensitive fatigue analysis of martensitic gear steels is developed as an outcome of this research; such tools and methodologies will lend quantitative and qualitative support to designing improved, fatigue-resistant materials and accelerating insertion of new or improved materials into service.

In this paper, we report that various kinds of active sites on graphite surface including active hydrophilic sites markedly affect the electrochemical performance of graphite anodes for lithium ion batteries under different humidity conditions. After depositing metals such as Ag and Cu by immersing and heat-treating, these active sites on the graphite surface were removed or covered and its electrochemical performance under the high humidity conditions was markedly improved. This suggests that lithium ion batteries can be assembled under less strict conditions and that it provides a valuable direction to lower the manufacturing cost for lithium ion batteries.

High rolling contact fatigue parts are vital for the long service life of fuel pumps. Cummins Fuel Systems are currently using an M2 tool steel for one of the most important roller bearing application in their pumps, namely the cam follower. The future design of the cam follower is a pin-less tappet roller. The wear and fatigue properties of the roller is vital to ensure reliability of the fuel system. M2 tool steel is an expensive material and becomes even more so if diamond like coating (DLC) is needed to decrease the friction coefficients. To cut costs of the fuel pump it might be possible to replace the M2 tool steel with 52100 steel (100Cr6). Competitive methods have proven that carbonitrided 52100 can reach excellent wear and fatigue properties making it a candidate to replace M2 tool steel. How the properties of hardness, toughness and compressive residual stresses are developed in 52100 and how they affect the fatigue and wear resistance has been researched from the literature. A big part of this project was to do an extensive analysis of a roller bearing that was believed to have gone through one of these competitive methods that produce excellent wear and fatigue resistance. The analysis was done with background to the knowledge gathered from the literature. Finally process trials were set up to carbonitride 52100 steel samples. The trials were done to develop a better understanding of how adding carbon together with nitrogen to the surface of 52100 steel will influence the metallurgical parameters that results in good wear and fatigue resistance. From this analysis Cummins hope to create a process recipe that can be used for carbonitriding the cam follower and maybe other components in their fuel systems.

Το αντικείμενο της παρούσας διατριβής είναι η ανάπτυξη μεθοδολογίας προσδιορισμού της κατανομής της σκληρότητας και του βάθους διείσδυσης της σκλήρυνσης που προκαλείται σε ένα εξάρτημα το οποίο έχει υποστεί Σκλήρυνση μέσω Λείανσης (Grind-Hardening). Η διεργασία Σκλήρυνσης μέσω Λείανσης είναι μία νέα επιφανειακή θερμική κατεργασία η οποία χρησιμοποιεί την θερμότητα που αναπτύσσεται στην ζώνη λείανσης για την θερμική κατεργασία του κομματιού. Η παρούσα διατριβή επικεντρώνεται στην ανάπτυξη μαθηματικών μοντέλων ικανών να προβλέψουν τα διάφορα χαρακτηριστικά της διεργασίας (δηλ. τη τοπογραφία της επιφάνειας του λειαντικού τροχού, τις δυνάμεις κατεργασίας, την παραγωγή και τον επιμερισμό της θερμότητας και την θερμοκρασιακή κατανομή). Τα μοντέλα αυτά συνδυαζόμενα επιτρέπουν τον προσδιορισμό της κατανομής σκληρότητας και του βάθος δι-είσδυσης της σκλήρυνσης συναρτήσει των παραμέτρων της διεργασίας και των χαρακτηριστικών του λειαντικού τροχού που χρησιμοποιείται. Παράλληλα, η εφαρμογή των μοντέλων αυτών οδηγεί σε χρήσιμα συμπεράσματα σχετικά με τα όρια εφαρμογής της διεργασίας. Μετά την επιβεβαίωση των θεωρητικών προβλέψεων, εξάχθηκε βάση δεδομένων υπολογισμού του βάθους διείσδυσης της σκλήρυνσης συναρτήσει της ροής θερμότητας στο κομμάτι και των παραμέτρων της διεργασίας. Η μεθοδολογία που αναπτύχθηκε εφαρμόστηκε για την περίπτωση σκλήρυνσης οδηγών κύλισης (raceway). Το σημαντικότερο συμπέρασμα που προκύπτει από την συγκεκριμένη διατριβή είναι ότι η διεργασία σκλήρυνσης μέσω λείανσης μπορεί να θεωρηθεί αρκετά «ώριμη» ούτως ώστε να μπορεί να εισαχθεί στην βιομηχανική πρακτική για την επιφανειακή σκλήρυνση εξαρτημάτων. Τα διάφορα χαρακτηριστικά της διεργασίας μπορούν να προβλεφθούν ενώ τέθηκαν οι βάσεις δημιουργίας ενός συστήματος παρακολούθησης και προγραμματισμού της διεργασίας. / The objective of the present study is the development of a methodology capable of predicting the hardness distribution and the hardness penetration within a grind-hardened workpiece. Grind-hardening is a novel-alternative surface hardening process that utilizes the heat generated in the grinding zone for the heat treatment of the workpiece material. The present work has employed analytical and numerical modeling techniques for describing the characteristics and output of the process, i.e. the topography of the grinding wheel, the process induced forces, the heat generation and partition and the temperature distribution within the work-piece. These models when coupled allow the estimation of the hardness distribution and the hardness penetration depth as a function of the process parameters and the characteristics of the grinding wheel. Additionally, through the process modeling, the process limitations are identified. After proving the validity of the theoretical predictions, the coupled models were utilized for the extraction of a data base providing the hardness penetration depth as a function of the heat flow entering the workpiece and the process parameters. The developed methodology was used for programming the grind-hardening of raceways. The main conclusion of this work is that grind-hardening process can be nowadays introduced in the industrial practice. The methodology developed, allows the prediction of the process outcome and can be used in the future for setting up an on-line monitoring system and / or develop an off-line process programming system.

Qualitative and quantitative research methods were employed to evaluate the acceptability and feasibility of HIV-1 infected, urban South African mothers being able to feed their infants heat-treated expressed breast milk (HTEBM). Nutritional status assessment of HIV-infected breastfeeding mothers (n=84) indicated that maternal status was not compromised; mean body mass index 26.8 (4.0) kg/m2, triceps skinfold 14.8 (5.50) mm and hemoglobin 11.6 (1.49) g/dL. However, severely immunocompromised mothers (CD4 + < 200 cells/mm3) were more likely to be anemic. Breastmilk viral loads were also higher in mothers with lower CD4+ cell counts. Community based inquiry on the acceptability of HTEBM was accomplished through in-depth interviews of participants (n=31), at the individual (mothers), family (partners, grandparents, mothers-in-law) and at the community level (traditional healers, daycare worker, health care counselors). Although an unfamiliar concept for all interviewed, overall, HTEBM was found to be an acceptable feeding choice regardless of respondents' gender, age, maternal status, family or community role. Further, data indicated mothers rarely received quality infant feeding counseling, consequently mixed feeding, a high risk for HIV transmission, was a common practice. In a pilot longitudinal study, using mixed-methods, the feasibility of mothers successfully implementing a modified breastfeeding intervention (6 months exclusive breastfeeding (EBF), cessation of breastfeeding, followed by use of HTEBM with complementary diet) was evaluated. The majority of mothers (36/66) practiced EBF for 6 months, 42% of whom also used HTEBM, expressing a range of approximately, 65 ml to 600 ml of breastmilk daily, for varying durations (2 weeks to 5 months). Mothers did not experience breast pathology. Home visits were highly enabling as was disclosure of HIV status to a partner. This is the first study to demonstrate that use of HTEBM is a feasible infant feeding option for HIV infected women. HTEBM may offer one solution to reduce vertical transmission of HIV and help maintain nutritional adequacy, as a component of complementary feeding.