The Role of Friction Stir Processing (FSP) Parameters on TiC Reinforced Surface Al7075-T651 Aluminum Alloy

Abstract

Aluminum alloys are very promising for structural applications in aerospace, military and transportation industries due to their light weight, high strength-to-weight ratio and excellent resistance to corrosion. In comparison to unreinforced aluminum alloys, aluminum/aluminum alloy matrix composites reinforced with ceramic phases exhibit higher strength and hardness, improved tribological characteristics. A novel surface modifying technique, friction stir processing (FSP), has been developed for fabrication of surface composite with an improved performance. The effect of FSP parameters such as number of passes, direction of each pass, sealed or unsealed groove on microstructure was investigated. In this work, nano-particles of TiC (2% in weight) were added to aluminum alloy AA7075-T651 to produce a functional surface. Fixed parameters for this AA7075 alloy were used; rotation speed of 1000 rpm, travel speed of 300 mm/min and pin penetration of 2.8 mm. Optical microscopy (OM), scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed to study the microstructure of the fabricated surface composites. The results indicated that the selected FSP parameters influenced the area of surface composite, distribution of TiC particles and micro-hardness of the surface composites. Finally, in order to evaluate rate wear the pin on disk test was carried out. Key-words:Friction Stir Processing (FSP); Nano-particles; Aluminum alloy 7075; Surface composite; Wear. Efeito dos Parâmetros do Proceso de Fricção Agitação para Reforçar Uma Placa de Aluminio Al7075-T651 com TiCResumo: As ligas de alumínio são promissoras para aplicações estruturais nas indústrias aeroespaciais e de transporte devido ao seu elevada relação resistência-peso e excelente resistência à corrosão. Em comparação com as ligas de alumínio não reforçadas e alumínio/compósitos de matriz de alumínio reforçados com fases cerâmicas, exibem maior resistência e características tribológicas melhoradas. Foi desenvolvida uma técnica de modificação superficial, friction stir processing, para a fabricação de superfície de compósitos. Foi investigado o efeito dos parâmetros FSP como número de passes, direção de cada passe e ranhura selado ou não selada. Neste trabalho, nanopartículas de TiC (2% em peso) foram adicionadas à liga de alumínio AA7075-T651 para produzir uma superfície funcional. Foram utilizados parâmetros fixos para a liga AA7075: velocidade de rotação de 1000 rpm, velocidade de deslocamento de 300 mm/min e penetração do pino de 2,8 mm. Microscopia óptica (MO), microscopia eletrônica de varredura (MEV) e microscopia de força atômica (AFM) foram utilizadas para estudar a microestrutura. Os resultados indicaram que os parâmetros FSP selecionados influenciaram na área da superfície do compósito, na distribuição de partículas de TiC e na microdureza da superfície. Finalmente, a fim de avaliar a taxa de desgaste o teste de pino sobre disco foi realizado. Palavras-chave:Processamento por Fricção Agitação (FSP); Nanopartículas; Liga de ...

Review of Friction Stir Processing (FSP) Parameters and Materials for Surface Composites

“…This can be explained with strength and wear resistance increase and reduction in contact area between the steel counterpart and fabricated composite rather than changing in the material structure [10]. García-Vázquez et al, [14] exhibited increases in wear rate coefficient comparing to the Al 7075 substrate. Palanivel et al [15] used FSP process to add TiB2 powder as reinforcement into AA7075 which led to the sliding wear resistance increase.…”

“…Adding TiB2 particles to AA6063 matrix increased hardness from 55 HV to 140 HV (2.5 times) [13]. García-Vázquez et al [14] showed that Al7075 substrate material has higher hardness than Al/TiC FSP fabricated composite. Similar reports can be found also in other literature [18][19][20]37].…”

“…The authors have also concluded that with the larger increase of TPD (0.35 mm) defects appear in the stir zone. On the other hand, with some other material combinations (TiC Reinforced Surface Al7075-T651 Aluminium Alloy), almost no cracks and voids appeared except of very small amount within the stir zone [14]. Palanivel et al [15] identified TiB2 and BN particles homogeneously dispersed throughout the aluminium matrix.…”

“…In order to create the surface composites by FSP method, two approaches are commonly used: by grooves, or by drilled holes [2]. The grooves or holes are machined on the surface, and further filled with a reinforcement particles, as shown in Figure 2 [8][9][10][11][12][13][14][15][16][17][18][19][20]. There are several approaches that can be used, but the widely investigated one is to start with FSP with pin-less tool over these filled grooves, followed by the repeated FSP by using the tool with a pin to homogenously distribute reinforcements.…”

“…Narimani et al [13] achieved relatively uniform TiB2 distribution with four passes. García-Vázquez et al [14] examined one-and two-pass FSP processes where two passes showed better results in hardness and wear resistance, compared to only one pass. In their study, Mirjavadi et al [16], investigated the influence of multi-pass FSP on AA5803/ZrO2 composite microstructure, mechanical and wear properties and found out that multi-pass FSP improves tensile properties consistently, with pass number increase, while wear rate decreased with pass number increase.…”