不锈钢和钛合金选区激光熔化成形工艺与性能研究

发布时间：2018-11-01 15:31

【摘要】：选区激光熔化技术(Selective Laser Melting, SLM)是一种应用较广泛的增材制造技术,凭借其制造精度高、制造结构复杂和个性化等优势,越来越受到社会的关注。316L不锈钢和Ti-6Al-4V合金因其优良的性能在医疗与航空航天领域有着较大的应用空间。但是上述两合金SLM成形过程的组织与性能研究还不完善,其缺陷的控制技术还没成熟。为此,本课题对SLM成形316L不锈钢和Ti-6Al-4V合金的组织与性能进行了详细的研究。首先,考察了离焦打印与焦点打印对316L不锈钢组织与性能的影响;接着,考察了不同SLM工艺参数和热处理工艺对316L不锈钢和Ti-6Al-4V合金的缺陷、组织、拉伸力学性能、硬度和压缩性能的影响,从而确定较佳的SLM工艺参数和热处理工艺,从而为316L不锈钢和Ti-6Al-4V合金的3D打印应用提供技术支撑。本课题得出的主要结论如下:(1)焦点打印优于离焦打印,采用不同工艺参数正交试验,得出的316L不锈钢较优工艺参数组合为扫描间距S=0.05mm,扫描速度V=1500 mm/s,扫描功率P=450W,在此工艺下样品的致密度达到95.9%; Ti-6Vl-4V合金较优工艺参数组合为扫描间距S=0.07 mm,扫描速度V=2500mm/s,扫描功率P=450W,此工艺下的致密度为98.1%。(2) SLM成形的316L不锈钢组织主要由细小的柱状组织以及蜂窝状组织组成。其室温拉伸抗拉强度为645 MPa,屈服强度为560 MPa,伸长率达45%。其拉伸断口出现韧窝,表现为典型的韧性断裂。(3) 316L不锈钢在热处理后组织呈现出单一奥氏体组织,并且随热处理温度升高,晶粒发生长大,从而使熔合线搭接消失;通过热处理可以调节制件的力学性能,在750℃保温2h并随炉冷却的热处理工艺下,其表现出了较好的拉伸性能,其中抗拉强度为680MPa,屈服强度为480MPa;在1000℃保温lh并随炉冷的热处理工艺下,其延伸率最好,高达56%。(4) SLM成形的Ti-6All4V合金组织主要为细小针状的α'马氏体组织,其室温拉伸抗拉强度为1250MPa,屈服强度为1160MPa,延伸率仅8.0%,断口有撕裂棱,呈现出准解理断裂;抗压强度高于其抗拉强度,为1755Mpa;经850℃真空热处理后,组织发生了明显的粗化,且较均匀,此时的室温拉伸抗拉强度为1010 MPa,屈服强度为950 MPa,延伸率为9.00%。拉伸断口有大小不一的韧窝出现,塑性有所增强。
[Abstract]:Selective laser melting technology (Selective Laser Melting, SLM) is a widely used material increasing manufacturing technology, which has the advantages of high manufacturing precision, complex manufacturing structure and individuation. 316L stainless steel and Ti-6Al-4V alloys have great application space in medical and aerospace fields because of their excellent properties. However, the microstructure and properties of the two alloys in SLM forming process are not perfect, and the defect control technology is not mature. Therefore, the microstructure and properties of 316L stainless steel and Ti-6Al-4V alloy formed by SLM were studied in detail. Firstly, the effects of defocus printing and focus printing on the microstructure and properties of 316L stainless steel were investigated. Then, the effects of different SLM process parameters and heat treatment on the defects, microstructure, tensile mechanical properties, hardness and compression properties of 316L stainless steel and Ti-6Al-4V alloy were investigated, and the better SLM process parameters and heat treatment process were determined. It provides technical support for the application of 316L stainless steel and Ti-6Al-4V alloy in 3D printing. The main conclusions of this paper are as follows: (1) focus printing is superior to defocus printing. By orthogonal test of different process parameters, the optimum process parameters of 316L stainless steel are as follows: scanning distance S0. 05 mm, scanning speed V1 500 mm/s,. The scanning power is 450W, and the density of the sample reaches 95.9 under this process. The optimum process parameters of Ti-6Vl-4V alloy are as follows: scanning interval S0. 07 mm, scanning speed VN 2 500 mm / s, scanning power PX 450 W, (2) the microstructure of 316L stainless steel formed by SLM is mainly composed of fine columnar structure and honeycomb structure. The tensile strength at room temperature is 645 MPa, and the yield strength is 560 MPa,. (3) the microstructure of 316L stainless steel shows a single austenitic structure after heat treatment, and the grain grows up with the increase of heat treatment temperature, which makes the fusion line lap disappear; (3) the tensile fracture of stainless steel is characterized by ductile fracture. (3) the microstructure of 316L stainless steel shows a single austenitic structure after heat treatment. The mechanical properties of the parts can be adjusted by heat treatment. The tensile strength and yield strength are 680MPa and 480MPa respectively, and the tensile strength is 680MPa and the yield strength is 480MPa under the heat treatment process of 750 鈩，

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