Jack Lowe died at the scene on parkland off Cook Street just after 9pm on Wednesday, despite the best efforts of paramedics to save him.
Three teenagers – two aged 18 and a 16-year-old – were arrested on suspicion of murder.
Police say they have now been granted extra time to question the 16-year-old boy and 18-year-old man, but the other 18-year-old has been released with no further action.
Emotional messages have been left alongside floral tributes and a photograph of the young victim at the scene.
One read: "I can't believe you've gone so soon. "I'll never ever forget all of our good memories and that's a promise.
"I love you so much. The pit in my stomach is horrible."
Another said: "You'll be missed. Taken too soon. Rest easy."
Further tributes have continued to pour in on social media.
One said: "Such an amazing guy, taken in such a cruel way. Jack, you were such a light to so many others in a time when we were all, including you, surrounded by the dark.
"Always there for a laugh, you never failed to make us smile. Rest easy bro, you'll live on with us in our hearts and all the fantastic memories we have with you."
Another said: " I’m absolutely heart broken, rest easy Jack Lowe another victim to knife crime.
"Thank you for the many months we spend laughing together I will treasure them forever."
A statement released by West Midlands Police today said: "We're continuing to question two teenagers on suspicion of a murder in Darlaston.
"We've been granted extra time to question a 16-year-old boy and an 18-year-old man in connection with the death.
"Another 18-year-old man who was arrested has been released with no further action.
"We're continuing to offer full support to the family of the man who died during this deeply distressing time.
"We know how shocking the death of someone so young is, and we're doing all we can to understand exactly what happened and bring whoever was responsible to justice.
"Our homicide unit can be contacted via live chat on our website or by calling 101 quoting log number 4105 of 7/12."