Development for manufacturing of functionally gradient material by friction-assisted extrusion

采用粉末压制工艺、烧结工艺和薄带摩擦挤压工艺研究了Ti-10at%Al复合粉末的各种粉末成型和烧结工艺，将压制好的Ti-10at%Al复合粉末的绿色坯件在600 ℃加热10 h，烧结材料的维氏硬度提高到HV=165，这是因为在Ti基体中形成了Ti和Al之间的非金属化合物相。当Ti-10at%Al的绿色坯件在800 ℃下加热1 h后进行压缩试验时，最大压缩真应力约为900 MPa，临界压缩真应变约为0.4。当Ti-90at%Al的压制绿色坯件通过薄带的摩擦辅助挤压变形时，薄带具有约200-250 MPa的高拉伸强度。当摩擦辅助挤压变形的Ti-50at%Al薄带在600 ℃加热10 h时，烧结的薄带的维氏硬度为HV= 0.0001，已经证实，功能梯度材料可以通过粉末成形和烧结工艺来制造，其中层压绿色部件由各种粉末混合物并烧结，或者通过摩擦辅助挤出挤出层压绿色部件并烧结。

Various powder forming and sintering processes for producing a Ti-Al composite material have been investigated by a powder compacting process, a sintering process and a friction-assisted extrusion process of thin strip developed by the authors.When a compacted green part of Ti-10at%Al composite powder was heated at 600 C during 10 h, the Vickers hardness of the sintered material was incresed upto HV=165, because an inetermetalic compound phase between Ti and Al was formed in Ti matrix. When a green part of Ti-10at%Al was heated at 800 C during 1 h and then the sintered part was tested by a compression test, the maximum compressive true stress was about 900 MPa and the critical compressive true strain was about 0.4.When a compacted green part of Ti-90at%Al was deformed by the friction-assisted extrusion of thin strip, the thin strip had a high tensile strength of about 200-250 MPa. When a thin strip of Ti-50at%Al deformed by friction-assisted extrusion was heated at 600 C during 10 h, the Vickers hardness of the sintered thin strip was HV=200 because of formation of intermetallic compound phase between Ti and Al.It has been confirmed that functionally graident materials are possible to be manufactured by the powder forming and sintering processes in which a laminate green part is compacted from various powder mixtures and sintered, or the laminate green part is extruded by the friction-assisted extrusion and sintered.