Thixoforging of continuous fiber-reinforced AlSi/AlMg-alloys

High strength in combination with low density is the key features for lightweight constructions in automotive and aerospace applications. Tailor-made fiber reinforcements in light-metal matrices could help to achieve this goal. However, the integration of fibers with conventional casting-route manufacturing techniques like squeeze casting or diffusion bonding restricts the component geometry and results in elevated process cost due to long cycle times and the need of additional fiber coatings. In the center of competence for casting and thixoforging Stuttgart (CCT), new processes for manufacturing metal matrix composites are developed. Long-fiber reinforced Al–Si alloys and components are produced by thixoforging of laminates made of alternating metal matrix layers and carbon fiber fabrics. This paper illustrates the manufacturing technology and first experimental results with special focus on fiber penetration and infiltration behavior and also on the formation of fiber-matrix interface to analyze fiber damage by mechanical or chemical attack.     

Investigation on microstructure and mechanical properties of Ti14 alloy after semisolid deformation

Abstract

This study details the development of microstructure of Ti14 alloy as a function of the forging temperature and forging ratio in semisolid state and influence of resulting microstructure on the mechanical properties. The results reveal that dynamic recrystallisation occurred during semisolid forging, and the grain refinement was attained. Grain size increased in the forging temperature and decreased in the forging ratio. High ultimate tensile strengths and low elongation have been achieved after semisolid forging. The strength decreased with increasing forging temperature, while the ductility increased with increasing forging ratio. The relative contributions of tensile properties were attributed to the varieties of grain size obtained by thixoforging.     

半固态AlSi7Mg合金坯料连续制备和触变成形研究

系统研究了半固态AlSi7Mg合金连铸坯料的制备和触变成形。研究表明:在电磁搅拌下,制备出半固态AlSi7Mg合金连铸坯料,合适的连铸速度为1.5～3 mm/s;半固态AlSi7Mg合金坯料的合适加热温度为580～590℃;在模具温度100～300℃和比压15～25 MPa条件下,触变锻造出汽车制动总泵体和比例阀毛坯。     

Microstructural evolution and tensile mechanical properties of thixoforged ZK60-Y magnesium alloys produced by two different routes

Semi-solid processing of magnesium alloys is generally based on conventional magnesium-based casting alloys such as Mg–Al series. However, these casting alloys do not give such high mechanical properties as the alloys that are conventionally wrought such as Mg–Zn series. In this paper, a ZK60 magnesium alloy with the addition of Y was thixoforged. The semi-solid thermal transformation (SSTT) route and the recrystallisation and partial melting (RAP) route were used to obtain the semi-solid feedstocks for thixoforging. Microstructural evolution during partial remelting was studied at temperatures for times. Tensile mechanical properties of thixoforged components at room temperature were examined. Results show that a fine spheroidal microstructure can be obtained by the RAP route. Compared to the RAP route, the SSTT alloy shows coarsened solid grains with a relatively high proportion of intragranular liquid droplets. With prolonged holding time, the solid grain sizes of the SSTT alloy and the RAP alloy increased. Coalescence was dominant in the SSTT alloy and Ostwald ripening was dominant in the RAP alloy. Thixoforging for the SSTT alloy and the RAP alloy resulted in successful filling of the die. The tensile properties of the thixoforged RAP alloy were satisfactory and exceeded those of the thixoforged SSTT alloy. However, the mechanical properties of both the thixoforged SSTT alloy and the thixoforged RAP alloy decreased with prolonged holding time.     

A study on manufacturing of aluminum automotive piston by thixoforging

The manufacture of many products related to the automobile and airplane industries by semi-solid forming is nowadays increasing from environmental and economical points of view. Especially in the automobile industry, to upgrade engine capability and reduce engine weight, the aluminum engine piston has already been developed by researchers and industrial technicians. Currently, forming methods to manufacture engine piston are casting, squeeze casting and hot forging. These methods, however, include several casting defects and need post machining as well. In this study, aluminum engine piston will be manufactured by thixoforging according to forming variables. In addition, it is very important to find the effects of forming variables on the final product by thixoforging. In order to determine the effects, however, researchers and industrial technicians have depended upon many experimental trials. In this study, a statistical approach for thixoforging has been adopted to improve experimental efficiency. Forming variables such as initial solid fraction, die temperature, and compression holding time were considered for manufacturing aluminum engine piston by thixoforging. Hardness and microstructure characterization were carried out so that the optimal forming condition could be found by the statistical approach. The experiment to make aluminum engine piston was performed under the optimal condition found by the statistical approach.